Commit 82b19c4c authored by Marcel Stör's avatar Marcel Stör
Browse files

Merge branch 'newdocs' into dev

parents 7e8c5489 96a05dcd
......@@ -2,6 +2,7 @@
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###A lua based firmware for wifi-soc esp8266
- Build on [ESP8266 NONOS SDK 1.5.1](http://bbs.espressif.com/viewtopic.php?f=46&p=5315)
......@@ -411,173 +412,6 @@ Victor Brutskiy's [ESPlorer](https://github.com/4refr0nt/ESPlorer) is written in
package.loaded["ds18b20"]=nil
```
####Operate a display with u8glib
u8glib is a graphics library with support for many different displays. The nodemcu firmware supports a subset of these.
Both I2C and SPI:
* sh1106_128x64
* ssd1306 - 128x64 and 64x48 variants
* ssd1309_128x64
* ssd1327_96x96_gr
* uc1611 - dogm240 and dogxl240 variants
SPI only:
* ld7032_60x32
* pcd8544_84x48
* pcf8812_96x65
* ssd1322_nhd31oled - bw and gr variants
* ssd1325_nhd27oled - bw and gr variants
* ssd1351_128x128 - gh and hicolor variants
* st7565_64128n - variants 64128n, dogm128/132, lm6059/lm6063, c12832/c12864
* uc1601_c128032
* uc1608 - 240x128 and 240x64 variants
* uc1610_dogxl160 - bw and gr variants
* uc1611 - dogm240 and dogxl240 variants
* uc1701 - dogs102 and mini12864 variants
U8glib v1.18.1
#####I2C connection
Hook up SDA and SCL to any free GPIOs. Eg. [u8g_graphics_test.lua](lua_examples/u8glib/u8g_graphics_test.lua) expects SDA=5 (GPIO14) and SCL=6 (GPIO12). They are used to set up nodemcu's I2C driver before accessing the display:
```lua
sda = 5
scl = 6
i2c.setup(0, sda, scl, i2c.SLOW)
```
#####SPI connection
The HSPI module is used ([more information](http://d.av.id.au/blog/esp8266-hardware-spi-hspi-general-info-and-pinout/)), so certain pins are fixed:
* HSPI CLK = GPIO14
* HSPI MOSI = GPIO13
* HSPI MISO = GPIO12 (not used)
All other pins can be assigned to any available GPIO:
* CS
* D/C
* RES (optional for some displays)
Also refer to the initialization sequence eg in [u8g_graphics_test.lua](lua_examples/u8glib/u8g_graphics_test.lua):
```lua
spi.setup(1, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, 8, 8)
```
#####Library usage
The Lua bindings for this library closely follow u8glib's object oriented C++ API. Based on the u8g class, you create an object for your display type.
SSD1306 via I2C:
```lua
sla = 0x3c
disp = u8g.ssd1306_128x64_i2c(sla)
```
SSD1306 via SPI:
```lua
cs = 8 -- GPIO15, pull-down 10k to GND
dc = 4 -- GPIO2
res = 0 -- GPIO16, RES is optional YMMV
disp = u8g.ssd1306_128x64_hw_spi(cs, dc, res)
```
This object provides all of u8glib's methods to control the display.
Again, refer to [u8g_graphics_test.lua](lua_examples/u8glib/u8g_graphics_test.lua) to get an impression how this is achieved with Lua code. Visit the [u8glib homepage](https://github.com/olikraus/u8glib) for technical details.
#####Displays
I2C and HW SPI based displays with support in u8glib can be enabled. To get access to the respective constructors, add the desired entries to the I2C or SPI display tables in [app/include/u8g_config.h](app/include/u8g_config.h):
```c
#define U8G_DISPLAY_TABLE_I2C \
U8G_DISPLAY_TABLE_ENTRY(ssd1306_128x64_i2c) \
#define U8G_DISPLAY_TABLE_SPI \
U8G_DISPLAY_TABLE_ENTRY(ssd1306_128x64_hw_spi) \
U8G_DISPLAY_TABLE_ENTRY(pcd8544_84x48_hw_spi) \
U8G_DISPLAY_TABLE_ENTRY(pcf8812_96x65_hw_spi) \
```
An exhaustive list of available displays can be found in the [u8g module wiki entry](https://github.com/nodemcu/nodemcu-firmware/wiki/nodemcu_api_en#u8g-module).
#####Fonts
u8glib comes with a wide range of fonts for small displays. Since they need to be compiled into the firmware image, you'd need to include them in [app/include/u8g_config.h](app/include/u8g_config.h) and recompile. Simply add the desired fonts to the font table:
```c
#define U8G_FONT_TABLE \
U8G_FONT_TABLE_ENTRY(font_6x10) \
U8G_FONT_TABLE_ENTRY(font_chikita)
```
They'll be available as `u8g.<font_name>` in Lua.
#####Bitmaps
Bitmaps and XBMs are supplied as strings to `drawBitmap()` and `drawXBM()`. This off-loads all data handling from the u8g module to generic methods for binary files. See [u8g_bitmaps.lua](lua_examples/u8glib/u8g_bitmaps.lua).
In contrast to the source code based inclusion of XBMs into u8glib, it's required to provide precompiled binary files. This can be performed online with [Online-Utility's Image Converter](http://www.online-utility.org/image_converter.jsp): Convert from XBM to MONO format and upload the binary result with [nodemcu-uploader.py](https://github.com/kmpm/nodemcu-uploader).
#####Unimplemented functions
- [ ] Cursor handling
- [ ] disableCursor()
- [ ] enableCursor()
- [ ] setCursorColor()
- [ ] setCursorFont()
- [ ] setCursorPos()
- [ ] setCursorStyle()
- [ ] General functions
- [ ] setContrast()
- [ ] setPrintPos()
- [ ] setHardwareBackup()
- [ ] setRGB()
- [ ] setDefaultMidColor()
####Operate a display with ucglib
Ucglib is a graphics library with support for color TFT displays.
Ucglib v1.3.3
#####SPI connection
The HSPI module is used ([more information](http://d.av.id.au/blog/esp8266-hardware-spi-hspi-general-info-and-pinout/)), so certain pins are fixed:
* HSPI CLK = GPIO14
* HSPI MOSI = GPIO13
* HSPI MISO = GPIO12 (not used)
All other pins can be assigned to any available GPIO:
* CS
* D/C
* RES (optional for some displays)
Also refer to the initialization sequence eg in [GraphicsTest.lua](lua_examples/ucglib/GraphicsRest.lua):
```lua
spi.setup(1, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, 8, 8)
```
#####Library usage
The Lua bindings for this library closely follow ucglib's object oriented C++ API. Based on the ucg class, you create an object for your display type.
ILI9341 via SPI:
```lua
cs = 8 -- GPIO15, pull-down 10k to GND
dc = 4 -- GPIO2
res = 0 -- GPIO16, RES is optional YMMV
disp = ucg.ili9341_18x240x320_hw_spi(cs, dc, res)
```
This object provides all of ucglib's methods to control the display.
Again, refer to [GraphicsTest.lua](lua_examples/ucglib/GraphicsTest.lua) to get an impression how this is achieved with Lua code. Visit the [ucglib homepage](https://github.com/olikraus/ucglib) for technical details.
#####Displays
To get access to the display constructors, add the desired entries to the display table in [app/include/ucg_config.h](app/include/ucg_config.h):
```c
#define UCG_DISPLAY_TABLE \
UCG_DISPLAY_TABLE_ENTRY(ili9341_18x240x320_hw_spi, ucg_dev_ili9341_18x240x320, ucg_ext_ili9341_18) \
UCG_DISPLAY_TABLE_ENTRY(st7735_18x128x160_hw_spi, ucg_dev_st7735_18x128x160, ucg_ext_st7735_18) \
```
#####Fonts
ucglib comes with a wide range of fonts for small displays. Since they need to be compiled into the firmware image, you'd need to include them in [app/include/ucg_config.h](app/include/ucg_config.h) and recompile. Simply add the desired fonts to the font table:
```c
#define UCG_FONT_TABLE \
UCG_FONT_TABLE_ENTRY(font_7x13B_tr) \
UCG_FONT_TABLE_ENTRY(font_helvB12_hr) \
UCG_FONT_TABLE_ENTRY(font_helvB18_hr) \
UCG_FONT_TABLE_ENTRY(font_ncenR12_tr) \
UCG_FONT_TABLE_ENTRY(font_ncenR14_hr)
```
They'll be available as `ucg.<font_name>` in Lua.
####Control a WS2812 based light strip
```lua
-- set the color of one LED on GPIO2 to red
......
......@@ -74,7 +74,7 @@ static int ICACHE_FLASH_ATTR bmp085_init(lua_State* L) {
bmp085_data.MC = r16(bmp085_i2c_id, 0xBC);
bmp085_data.MD = r16(bmp085_i2c_id, 0xBE);
return 1;
return 0;
}
static uint32_t bmp085_temperature_raw_b5(void) {
......
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# NodeMCU Dokumentation
NodeMCU ist eine [eLua](http://www.eluaproject.net/)-basierende firmware für den [ESP8266 WiFi SOC von Espressif](http://espressif.com/en/products/esp8266/). Dies ist ein Partnerprojekt für die beliebten [NodeMCU dev kits](https://github.com/nodemcu/nodemcu-devkit-v1.0) - open source NodeMCU boards mit ESP8266-12E chips.
Diese firmware nutzt das Espressif NON-OS SDK, das Dateisystem basiert auf [spiffs](https://github.com/pellepl/spiffs).
There are essentially three ways to build your NodeMCU firmware: cloud build service, Docker image, dedicated Linux environment (possibly VM).
## Cloud Build Service
NodeMCU "application developers" just need a ready-made firmware. There's a [cloud build service](http://nodemcu-build.com/) with a nice UI and configuration options for them.
## Docker Image
Occasional NodeMCU firmware hackers don't need full control over the complete tool chain. They might not want to setup a Linux VM with the build environment. Docker to the rescue. Give [Docker NodeMCU build](https://hub.docker.com/r/marcelstoer/nodemcu-build/) a try.
## Linux Build Environment
NodeMCU firmware developers commit or contribute to the project on GitHub and might want to build their own full fledged build environment with the complete tool chain. There is a [post in the esp8266.com Wiki](http://www.esp8266.com/wiki/doku.php?id=toolchain#how_to_setup_a_vm_to_host_your_toolchain) that describes this.
\ No newline at end of file
# FAQ
**# # # Work in Progress # # #**
*This was started by [Terry Ellison](https://github.com/TerryE) as an unofficial FAQ in mid 2015. It never became officially official and it is in need of an overhaul, see [#937](https://github.com/nodemcu/nodemcu-firmware/issues/937). Yet, it is still very valuable and is, therefore, included here.*
## What is this FAQ for?
This FAQ does not aim to help you to learn to program or even how to program in Lua. There are plenty of resources on the Internet for this, some of which are listed in [Where to start](#where-to-start). What this FAQ does is to answer some of the common questions that a competent Lua developer would ask in learning how to develop Lua applications for the ESP8266 based boards running the [NodeMcu](http://NodeMCU.com/index_en.html) firmware.
## Lua Language
### Where to start
The NodeMCU firmware implements Lua 5.1 over the Espressif SDK for its ESP8266 SoC and the IoT modules based on this.
* The official lua.org **[Lua Language specification](http://www.lua.org/manual/5.1/manual.html)** gives a terse but complete language specification.
* Its [FAQ](http://www.lua.org/faq.html) provides information on Lua availability and licensing issues.
* The **[unofficial Lua FAQ](http://www.luafaq.org/)** provides a lot of useful Q and A content, and is extremely useful for those learning Lua as a second language.
* The [Lua User's Wiki](http://lua-users.org/wiki/) gives useful example source and relevant discussion. In particular, its [Lua Learning Lua](http://lua-users.org/wiki/Learning) section is a good place to start learning Lua.
* The best book to learn Lua is *Programming in Lua* by Roberto Ierusalimschy, one of the creators of Lua. It's first edition is available free [online](http://www.lua.org/pil/contents.html) . The second edition was aimed at Lua 5.1, but is out of print. The third edition is still in print and available in paperback. It contains a lot more material and clearly identifies Lua 5.1 vs Lua 5.2 differences. **This third edition is widely available for purchase and probably the best value for money**. References of the format [PiL **n.m**] refer to section **n.m** in this edition.
* The Espressif ESP8266 architecture is closed source, but the Espressif SDK itself is continually being updated so the best way to get the documentation for this is to [google Espressif IoT SDK Programming Guide](https://www.google.co.uk/search?q=Espressif+IoT+SDK+Programming+Guide) or to look at the Espressif [downloads forum](http://bbs.espressif.com/viewforum.php?f=5) .
* The **[NodeMCU documentation](http://www.NodeMCU.com/docs/)** is available online. However, please remember that the development team are based in China, and English is a second language, so the documentation needs expanding and be could improved with technical proofing.
* As with all Open Source projects the source for the NodeMCU firmware is openly available on the [GitHub NodeMCU-firmware](https://github.com/NodeMCU/NodeMCU-firmware) repository.
### How is NodeMCU Lua different to standard Lua?
Whilst the Lua standard distribution includes a host stand-alone Lua interpreter, Lua itself is primarily an *extension language* that makes no assumptions about a "main" program: Lua works embedded in a host application to provide a powerful, light-weight scripting language for use within the application. This host application can then invoke functions to execute a piece of Lua code, can write and read Lua variables, and can register C functions to be called by Lua code. Through the use of C functions, Lua can be augmented to cope with a wide range of different domains, thus creating customized programming languages sharing a syntactical framework.
The ESP8266 was designed and is fabricated in China by [Espressif Systems](http://espressif.com/new-sdk-release/). Espressif have also developed and released a companion software development kit (SDK) to enable developers to build practical IoT applications for the ESP8266. The SDK is made freely available to developers in the form of binary libraries and SDK documentation. However this is in a *closed format*, with no developer access to the source files, so ESP8266 applications *must* rely solely on the SDK API (and the somewhat Spartan SDK API documentation).
The NodeMCU Lua firmware is an ESP8266 application and must therefore be layered over the ESP8266 SDK. However, the hooks and features of Lua enable it to be seamlessly integrated without loosing any of the standard Lua language features. The firmware has replaced some standard Lua modules that don't align well with the SDK structure with ESP8266-specific versions. For example, the standard `io` and `os` libraries don't work, but have been largely replaced by the NodeMCU `node` and `file` libraries. The `debug` and `math` libraries have also been omitted to reduce the runtime footprint.
NodeMCU Lua is based on [eLua](http://www.eluaproject.net/overview), a fully featured implementation of Lua 5.1 that has been optimized for embedded system development and execution to provide a scripting framework that can be used to deliver useful applications within the limited RAM and Flash memory resources of embedded processors such as the ESP8266. One of the main changes introduced in the eLua fork is to use read-only tables and constants wherever practical for library modules. On a typical build this approach reduces the RAM footprint by some 20-25KB and this makes a Lua implementation for the ESP8266 feasible. This technique is called LTR and this is documented in detail in an eLua technical paper: [Lua Tiny RAM](http://www.eluaproject.net/doc/master/en_arch_ltr.html).
The mains impacts of the ESP8266 SDK and together with its hardware resource limitations are not in the Lua language implementation itself, but in how *application programmers must approach developing and structuring their applications*. As discussed in detail below, the SDK is non-preemptive and event driven. Tasks can be associated with given events by using the SDK API to registering callback functions to the corresponding events. Events are queued internally within the SDK, and it then calls the associated tasks one at a time, with each task returning control to the SDK on completion. *The SDK states that if any tasks run for more than 10 mSec, then services such as Wifi can fail.*
The NodeMCU libraries act as C wrappers around registered Lua callback functions to enable these to be used as SDK tasks. ***You must therefore use an Event-driven programming style in writing your ESP8266 Lua programs***. Most programmers are used to writing in a procedural style where there is a clear single flow of execution, and the program interfaces to operating system services by a set of synchronous API calls to do network I/O, etc. Whilst the logic of each individual task is procedural, this is not how you code up ESP8266 applications.
## ESP8266 Specifics
### How is coding for the ESP8266 the same as standard Lua?
* This is a fully featured Lua 5.1 implementation so all standard Lua language constructs and data types work.
* The main standard Lua libraries -- `core`, `coroutine`, `string` and `table` are implemented.
### How is coding for the ESP8266 different to standard Lua?
* The ESP8266 use onchip RAM and offchip Flash memory connected using a dedicated SPI interface. Both of these are *very* limited (when compared to systems than most application programmer use). The SDK and the Lua firmware already use the majority of this resource: the later build versions keep adding useful functionality, and unfortunately at an increased RAM and Flash cost, so depending on the build version and the number of modules installed the runtime can have as little as 17KB RAM and 40KB Flash available at an application level. This Flash memory is formatted an made available as a **SPI Flash File System (SPIFFS)** through the `file` library.
* However, if you choose to use a custom build, for example one which uses integer arithmetic instead of floating point, and which omits libraries that aren't needed for your application, then this can help a lot doubling these available resources. (See Marcel Stör's excellent [custom build tool](http://frightanic.com/NodeMCU-custom-build/) that he discusses in [this forum topic](http://www.esp8266.com/viewtopic.php?f=23&t=3001)). Even so, those developers who are used to dealing in MB or GB of RAM and file systems can easily run out of these resources. Some of the techniques discussed below can go a long way to mitigate this issue.
* Current versions of the ESP8266 run the SDK over the native hardware so there is no underlying operating system to capture errors and to provide graceful failure modes, so system or application errors can easily "PANIC" the system causing it to reboot. Error handling has been kept simple to save on the limited code space, and this exacerbates this tendency. Running out of a system resource such as RAM will invariably cause a messy failure and system reboot.
* There is currently no `debug` library support. So you have to use 1980s-style "binary-chop" to locate errors and use print statement diagnostics though the systems UART interface. (This omission was largely because of the Flash memory footprint of this library, but there is no reason in principle why we couldn't make this library available in the near future as an custom build option).
* The LTR implementation means that you can't easily extend standard libraries as you can in normal Lua, so for example an attempt to define `function table.pack()` will cause a runtime error because you can't write to the global `table`. (Yes, there are standard sand-boxing techniques to achieve the same effect by using metatable based inheritance, but if you try to use this type of approach within a real application, then you will find that you run out of RAM before you implement anything useful.)
* There are standard libraries to provide access to the various hardware options supported by the hardware: WiFi, GPIO, One-wire, I²C, SPI, ADC, PWM, UART, etc.
* The runtime system runs in interactive-mode. In this mode it first executes any `init.lua` script. It then "listens" to the serial port for input Lua chunks, and executes them once syntactically complete. There is no `luac` or batch support, although automated embedded processing is normally achieved by setting up the necessary event triggers in the `init.lua` script.
* The various libraries (`net`, `tmr`, `wifi`, etc.) use the SDK callback mechanism to bind Lua processing to individual events (for example a timer alarm firing). Developers should make full use of these events to keep Lua execution sequences short. *If any individual task takes too long to execute then other queued tasks can time-out and bad things start to happen.*
* Non-Lua processing (e.g. network functions) will usually only take place once the current Lua chunk has completed execution. So any network calls should be viewed at an asynchronous request. A common coding mistake is to assume that they are synchronous, that is if two `socket:send()` are on consecutive lines in a Lua programme, then the first has completed by the time the second is executed. This is wrong. Each `socket:send()` request simply queues the send operation for dispatch. Neither will start to process until the Lua code has return to is calling C function. Stacking up such requests in a single Lua task function burns scarce RAM and can trigger a PANIC. This true for timer, network, and other callbacks. It is even the case for actions such as requesting a system restart, as can be seen by the following example:
```lua
node.restart(); for i = 1, 20 do print("not quite yet -- ",i); end
```
* You therefore *have* to implement ESP8266 Lua applications using an event driven approach. You have to understand which SDK API requests schedule asynchronous processing, and which define event actions through Lua callbacks. Yes, such an event-driven approach makes it difficult to develop procedurally structured applications, but it is well suited to developing the sorts of application that you will typically want to implement on an IoT device.
### So how does the SDK event / tasking system work in Lua?
* The SDK employs an event-driven and task-oriented architecture for programming at an applications level.
* The SDK uses a startup hook `void user_init(void)`, defined by convention in the C module `user_main.c`, which it invokes on boot. The `user_init()` function can be used to do any initialisation required and to call the necessary timer alarms or other SDK API calls to bind and callback routines to implement the tasks needed in response to any system events.
* The API provides a set of functions for declaring application functions (written in C) as callbacks to associate application tasks with specific hardware and timer events. These are non-preemptive at an applications level.
* Whilst the SDK provides a number of interrupt driven device drivers, the hardware architecture severely limits the memory available for these drivers, so writing new device drivers is not a viable options for most developers
* The SDK interfaces internally with hardware and device drivers to queue pending events.
* The registered callback routines are invoked sequentially with the associated C task running to completion uninterrupted.
* In the case of Lua, these C tasks are typically functions within the Lua runtime library code and these typically act as C wrappers around the corresponding developer-provided Lua callback functions. An example here is the Lua `tmr.alarm(id, interval, repeat, callback)` function. The calls a function in the `tmr` library which registers a C function for this alarm using the SDK, and when this C function is called it then invokes the Lua callback.
The NodeMCU firmware simply mirrors this structure at a Lua scripting level:
* A startup module `init.lua` is invoked on boot. This function module can be used to do any initialisation required and to call the necessary timer alarms or libary calls to bind and callback routines to implement the tasks needed in response to any system events.
* The Lua libraries provide a set of functions for declaring application functions (written in Lua) as callbacks (which are stored in the [Lua registry](#so-how-is-the-lua-registry-used-and-why-is-this-important)) to associate application tasks with specific hardware and timer events. These are non-preemptive at an applications level.
* The Lua libraries work in consort with the SDK to queue pending events and invoke any registered Lua callback routines, which then run to completion uninterrupted.
* Excessively long-running Lua functions can therefore cause other system functions and services to timeout, or allocate memory to buffer queued data, which can then trigger either the watchdog timer or memory exhaustion, both of which will ultimately cause the system to reboot.
* By default, the Lua runtime also 'listens' to UART 0, the serial port, in interactive mode and will execute any Lua commands input through this serial port.
This event-driven approach is very different to a conventional procedural implementation of Lua.
Consider a simple telnet example given in `examples/fragment.lua`:
```lua
s=net.createServer(net.TCP)
s:listen(23,function(c)
con_std = c
function s_output(str)
if(con_std~=nil) then
con_std:send(str)
end
end
node.output(s_output, 0)
c:on("receive",function(c,l) node.input(l) end)
c:on("disconnection",function(c)
con_std = nil
node.output(nil)
end)
end)
```
This example defines five Lua functions:
| Function | Defined in | Parameters | Callback? |
|-----------|------------|------------|-----------|
| Main | Outer module | ... (Not used) | |
| Connection listener | Main | c (connection socket) | |
| s_output | Connection listener | str | Yes |
| On Receive| Connection listener | c, l (socket, input) | Yes |
| On Disconnect | Connection listener | c (socket) | Yes |
`s`, `con_std` and `s_output` are global, and no [upvalues](#why-is-it-importance-to-understand-how-upvalues-are-implemented-when-programming-for-the-esp8266) are used. There is no "correct" order to define these in, but we could reorder this code for clarity (though doing this adds a few extra globals) and define these functions separately one another. However, let us consider how this is executed:
* The outer module is compiled including the four internal functions.
* `Main` is then assigning the created `net.createServer()` to the global `s`. The `connection listener` closure is created and bound to a temporary variable which is then passed to the `socket.listen()` as an argument. The routine then exits returning control to the firmware.
* When another computer connects to port 23, the listener handler retrieves the reference to then connection listener and calls it with the socket parameter. This function then binds the s_output closure to the global `s_output`, and registers this function with the `node.output` hook. Likewise the `on receive` and `on disconnection` are bound to temporary variables which are passed to the respective on handlers. We now have four Lua function registered in the Lua runtime libraries associated with four events. This routine then exits returning control to the firmware.
* When a record is received, the on receive handler within the net library retrieves the reference to the `on receive` Lua function and calls it passing it the record. This routine then passes this to the `node.input()` and exits returning control to the firmware.
* The `node.input` handler polls on an 80 mSec timer alarm. If a compete Lua chunk is available (either via the serial port or node input function), then it executes it and any output is then passed to the `note.output` handler. which calls `s_output` function. Any pending sends are then processed.
* This cycle repeats until the other computer disconnects, and `net` library disconnection handler then calls the Lua `on disconnect` handler. This Lua routine dereferences the connected socket and closes the `node.output` hook and exits returning control to the disconnect handler which garbage collects any associated sockets and registered on handlers.
Whilst this is all going on, The SDK can (and often will) schedule other event tasks in between these Lua executions (e.g. to do the actual TCP stack processing). The longest individual Lua execution in this example is only 18 bytecode instructions (in the main routine).
Understanding how the system executes your code can help you structure it better and improve memory usage. Each event task is established by a callback in an API call in an earlier task.
### So what Lua library functions enable the registration of Lua callbacks?
SDK Callbacks include:
| Lua Module | Functions which define or remove callbacks |
|------------|--------------------------------------------|
| tmr | `alarm(id, interval, repeat, function())` |
| node | `key(type, function())`, `output(function(str), serial_debug)` |
| wifi | `startsmart(chan, function())`, `sta.getap(function(table))` |
| net.server | `sk:listen(port,[ip],function(socket))` |
| net | `sk:on(event, function(socket, [, data]))`, `sk:send(string, function(sent))`, `sk:dns(domain, function(socket,ip))` |
| gpio | `trig(pin, type, function(level))` |
| mqqt | `client:m:on(event, function(conn[, topic, data])` |
| uart | `uart.on(event, cnt, [function(data)], [run_input])` |
### So how is context passed between Lua event tasks?
* It is important to understand that any event callback task is associated with a single Lua function. This function is executed from the relevant NodeMCU library C code using a `lua_call()`. Even system initialisation which executes the `dofile("init.lua")` can be treated as a special case of this. Each function can invoke other functions and so on, but it must ultimate return control to the C library code.
* By their very nature Lua `local` variables only exist within the context of an executing Lua function, and so all locals are destroyed between these `lua_call()` actions. *No locals are retained across events*.
* So context can only be passed between event routines by one of three mechanisms:
* **Globals** are by nature globally accessible. Any global will persist until explicitly dereference by reassigning `nil` to it. Globals can be readily enumerated by a `for k,v in pairs(_G) do` so their use is transparent.
* The **File system** is a special case of persistent global, so there is no reason in principle why it can't be used to pass context. However the ESP8266 file system uses flash memory and this has a limited write cycle lifetime, so it is best to avoid using the file system to store frequently changing content except as a mechanism of last resort.
* **Upvalues**. When a function is declared within an outer function, all of the local variables in the outer scope are available to the inner function. Since all functions are stored by reference the scope of the inner function might outlast the scope of the outer function, and the Lua runtime system ensures that any such references persist for the life of any functions that reference it. This standard feature of Lua is known as *closure* and is described in [Pil 6]. Such values are often called *upvalues*. Functions which are global or [[#So how is the Lua Registry used and why is this important?|registered]] callbacks will persist between event routines, and hence any upvalues referenced by them can be used for passing context.
### So how is the Lua Registry used and why is this important?
So all Lua callbacks are called by C wrapper functions that are themselves callback activated by the SDK as a result of a given event. Such C wrapper functions themselves frequently need to store state for passing between calls or to other wrapper C functions. The Lua registry is simply another Lua table which is used for this purpose, except that it is hidden from direct Lua access. Any content that needs to be saved is created with a unique key. Using a standard Lua table enables standard garbage collection algorithms to operate on its content.
Note that we have identified a number of cases where library code does not correctly clean up Registry content when closing out an action, leading to memory leaks.
### Why is it importance to understand how upvalues are implemented when programming for the ESP8266?
Routines directly or indirectly referenced in the globals table, **_G**, or in the Lua Registry may use upvalues. The number of upvalues associated with a given routine is determined by the compiler and a vector is allocated when the closure is bound to hold these references. Each upvalues is classed as open or closed. All upvalues are initially open which means that the upvalue references back to the outer functions's register set. However, upvalues must be able to outlive the scope of the outer routine where they are declared as a local variable. The runtime VM does this by adding extra checks when executing a function return to scan any defined closures within its scope for back references and allocate memory to hold the upvalue and points the upvalue's reference to this. This is known as a closed upvalue.
This processing is a mature part of the Lua 5.x runtime system, and for normal Lua applications development this "behind-the-scenes" magic ensures that upvalues just work as any programmer might expect. Sufficient garbage collector metadata is also stored so that these hidden values will be garbage collected correctly *when properly dereferenced*. However allocating these internal structures is quite expensive in terms of memory, and this hidden overhead is hard to track or to understand. If you are developing a Lua application for a PC where the working RAM for an application is measured in MB, then this isn't really an issue. However, if you are developing an application for the ESP8266 where you might have 20 KB for your program and data, this could prove a killer.
One further complication is that some library functions don't correctly dereference expired callback references and as a result their upvalues may not be correctly garbage collected (though we are tracking this down and hopefully removing this issue). This will all be manifested as a memory leak. So using upvalues can cause more frequent and difficult to diagnose PANICs during testing. So my general recommendation is still to stick to globals for this specific usecase of passing context between event callbacks, and `nil` them when you have done with them.
### Can I encapsulate actions such as sending an email in a Lua function?
Think about the implications of these last few answers.
* An action such as composing and sending an email involves a message dialogue with a mail server over TCP. This in turn requires calling multiple API calls to the SDK and your Lua code must return control to the C calling library for this to be scheduled, otherwise these requests will just queue up, you'll run out of RAM and your application will PANIC.
* Hence it is simply ***impossible*** to write a Lua module so that you can do something like:
```lua
-- prepare message
status = mail.send(to, subject, body)
-- move on to next phase of processing.
```
* But you could code up a event-driven task to do this and pass it a callback to be executed on completion of the mail send, something along the lines of the following. Note that since this involves a lot of asynchronous processing and which therefore won't take place until you've returned control to the calling library C code, you will typically execute this as the last step in a function and therefore this is best done as a tailcall [PiL 6.3].
```lua
-- prepare message
local ms = require("mail_sender")
return ms.send(to, subject, body, function(status) loadfile("process_next.lua")(status) end)
```
* Building an application on the ESP8266 is a bit like threading pearls onto a necklace. Each pearl is an event task which must be small enough to run within its RAM resources and the string is the variable context that links the pearls together.
### When and why should I avoid using tmr.delay()?
If you are used coding in a procedural paradigm then it is understandable that you consider using `tmr.delay()` to time sequence your application. However as discussed in the previous section, with NodeMCU Lua you are coding in an event-driven paradigm.
If you look at the `app/modules/tmr.c` code for this function, then you will see that it executes a low level `ets_delay_us(delay)`. This function isn't part of the NodeMCU code or the SDK; it's actually part of the xtensa-lx106 boot ROM, and is a simple timing loop which polls against the internal CPU clock. It does this with interrupts disabled, because if they are enabled then there is no guarantee that the delay will be as requested.
`tmr.delay()` is really intended to be used where you need to have more precise timing control on an external hardware I/O (e.g. lifting a GPIO pin high for 20 μSec). It will achieve no functional purpose in pretty much every other usecase, as any other system code-based activity will be blocked from execution; at worst it will break your application and create hard-to-diagnose timeout errors.
The latest SDK includes a caution that if any (callback) task runs for more than 10 mSec, then the Wifi and TCP stacks might fail, so if you want a delay of more than 8 mSec or so, then *using `tmr.delay()` is the wrong approach*. You should be using a timer alarm or another library callback, to allow the other processing to take place. As the NodeMCU documentation correctly advises (translating Chinese English into English): *`tmr.delay()` will make the CPU work in non-interrupt mode, so other instructions and interrupts will be blocked. Take care in using this function.*
### How do I avoid a PANIC loop in init.lua?
Most of us have fallen into the trap of creating an `init.lua` that has a bug in it, which then causes the system to reboot and hence gets stuck in a reboot loop. If you haven't then you probably will do so at least once.
* When this happens, the only robust solution is to reflash the firmware.
* The simplest way to avoid having to do this is to keep the `init.lua` as simple as possible -- say configure the wifi and then start your app using a one-time `tmr.alarm()` after a 2-3 sec delay. This delay is long enough to issue a `file.remove("init.lua")` through the serial port and recover control that way.
* Also it is always best to test any new `init.lua` by creating it as `init_test.lua`, say, and manually issuing a `dofile("init_test.lua")` through the serial port, and then only rename it when you are certain it is working as you require.
## Techniques for Reducing RAM and SPIFFS footprint
### How do I minimise the footprint of an application?
* Perhaps the simplest aspect of reducing the footprint of an application is to get its scope correct. The ESP8266 is an IoT device and not a general purpose system. It is typically used to attach real-world monitors, controls, etc. to an intranet and is therefore designed to implement functions that have limited scope. We commonly come across developers who are trying to treat the ESP8266 as a general purpose device and can't understand why their application can't run.
* The simplest and safest way to use IoT devices is to control them through a dedicated general purpose system on the same network. This could be a low cost system such as a [RaspberryPi (RPi)](https://www.raspberrypi.org/) server, running your custom code or an open source home automation (HA) application. Such systems have orders of magnitude more capacity than the ESP8266, for example the RPi has 2GB RAM and its SD card can be up to 32GB in capacity, and it can support the full range of USB-attached disk drives and other devices. It also runs a fully featured Linux OS, and has a rich selection of applications pre configured for it. There are plenty of alternative systems available in this under $50 price range, as well as proprietary HA systems which can cost 10-50 times more.
* Using a tiered approach where all user access to the ESP8266 is passed through a controlling server means that the end-user interface (or smartphone connector), together with all of the associated validation and security can be implemented on a system designed to have the capacity to do this. This means that you can limit the scope of your ESP8266 application to a limited set of functions being sent to or responding to requests from this system.
* *If you are trying to implement a user-interface or HTTP webserver in your ESP8266 then you are really abusing its intended purpose. When it comes to scoping your ESP8266 applications, the adage **K**eep **I**t **S**imple **S**tupid truly applies.*
### How do I minimise the footprint of an application on the file system
* It is possible to write Lua code in a very compact format which is very dense in terms of functionality per KB of source code.
* However if you do this then you will also find it extremely difficult to debug or maintain your application.
* A good compromise is to use a tool such as [LuaSrcDiet](http://luaforge.net/projects/luasrcdiet/), which you can use to compact production code for downloading to the ESP8266:
* Keep a master repository of your code on your PC or a cloud-based versioning repository such as [GitHub](https://github.com/)
* Lay it out and comment it for ease of maintenance and debugging
* Use a package such as [Esplorer](https://github.com/4refr0nt/ESPlorer) to download modules that you are debugging and to test them.
* Once the code is tested and stable, then compress it using LuaSrcDiet before downloading to the ESP8266. Doing this will reduce the code footprint on the SPIFFS by 2-3x.
* Consider using `node.compile()` to pre-compile any production code. This removes the debug information from the compiled code reducing its size by roughly 40%. (However this is still perhaps 1.5-2x larger than a LuaSrcDiet-compressed source format, so if SPIFFS is tight then you might consider leaving less frequently run modules in Lua format. If you do a compilation, then you should consider removing the Lua source copy from file system as there's little point in keeping both on the ESP8266.
### How do I minimise the footprint of running application?
* The Lua Garbage collector is very aggressive at scanning and recovering dead resources. It uses an incremental mark-and-sweep strategy which means that any data which is not ultimately referenced back to the Globals table, the Lua registry or in-scope local variables in the current Lua code will be collected.
* Setting any variable to `nil` dereferences the previous context of that variable. (Note that reference-based variables such as tables, strings and functions can have multiple variables referencing the same object, but once the last reference has been set to `nil`, the collector will recover the storage.
* Unlike other compile-on-load languages such as PHP, Lua compiled code is treated the same way as any other variable type when it comes to garbage collection and can be collected when fully dereferenced, so that the code-space can be reused.
* Lua execution is intrinsically divided into separate event tasks with each bound to a Lua callback. This, when coupled with the strong dispose on dereference feature, means that it is very easy to structure your application using an classic technique which dates back to the 1950s known as Overlays.
* Various approaches can be use to implement this. One is described by DP Whittaker in his [Massive memory optimization: flash functions](http://www.esp8266.com/viewtopic.php?f=19&t=1940) topic. Another is to use *volatile modules*. There are standard Lua templates for creating modules, but the `require()` library function creates a reference for the loaded module in the `package.loaded` table, and this reference prevents the module from being garbage collected. To make a module volatile, you should remove this reference to the loaded module by setting its corresponding entry in `package.loaded` to `nil`. You can't do this in the outermost level of the module (since the reference is only created once execution has returned from the module code), but you can do it in any module function, and typically an initialisation function for the module, as in the following example:
```lua
local s=net.createServer(net.TCP)
s:listen(80,function(c) require("connector").init(c) end)
```
* **`connector.lua`** would be a standard module pattern except that the `M.init()` routine must include the lines
```lua
local M, module = {}, ...
...
function M.init(csocket)
package.loaded[module]=nil
...
end
--
return M
```
* This approach ensures that the module can be fully dereferenced on completion. OK, in this case, this also means that the module has to be reloaded on each TCP connection to port 80; however, loading a compiled module from SPIFFS only takes a few mSec, so surely this is an acceptable overhead if it enables you to break down your application into RAM-sized chunks. Note that `require()` will automatically search for `connector.lc` followed by `connector.lua`, so the code will work for both source and compiled variants.
* Whilst the general practice is for a module to return a table, [PiL 15.1] suggests that it is sometimes appropriate to return a single function instead as this avoids the memory overhead of an additional table. This pattern would look as follows:
```lua
--
local s=net.createServer(net.TCP)
s:listen(80,function(c) require("connector")(c) end)
```
```lua
local module = _ -- this is a situation where using an upvalue is essential!
return function (csocket)
package.loaded[module]=nil
module = nil
...
end
```
* Also note that you should ***not*** normally code this up listener call as the following because the RAM now has to accommodate both the module which creates the server *and* the connector logic.
```lua
...
local s=net.createServer(net.TCP)
local connector = require("connector") -- don't do this unless you've got the RAM available!
s:listen(80,connector)
```
### How do I reduce the size of my compiled code?
Note that there are two methods of saving compiled Lua to SPIFFS:
- The first is to use `node.compile()` on the `.lua` source file, which generates the equivalent bytecode `.lc` file. This approach strips out all the debug line and variable information.
- The second is to use `loadfile()` to load the source file into memory, followed by `string.dump()` to convert it in-memory to a serialised load format which can then be written back to a `.lc` file. This approach creates a bytecode file which retains the debug information.
The memory footprint of the bytecode created by method (2) is the same as when executing source files directly, but the footprint of bytecode created by method (1) is typically **60% of this size**, because the debug information is almost as large as the code itself. So using `.lc` files generated by `node.compile()` considerably reduces code size in memory -- albeit with the downside that any runtime errors are extremely limited.
In general consider method (1) if you have stable production code that you want to run in as low a RAM footprint as possible. Yes, method (2) can be used if you are still debugging, but you will probably be changing this code quite frequently, so it is easier to stick with `.lua` files for code that you are still developing.
Note that if you use `require("XXX")` to load your code then this will automatically search for `XXX.lc` then `XXX.lua` so you don't need to include the conditional logic to load the bytecode version if it exists, falling back to the source version otherwise.
### How do I get a feel for how much memory my functions use?
* You should get an overall understanding of the VM model if you want to make good use of the limited resources available to Lua applications. An essential reference here is [A No Frills Introduction to Lua 5.1 VM Instructions](http://luaforge.net/docman/83/98/ANoFrillsIntroToLua51VMInstructions.pdf) . This explain how the code generator works, how much memory overhead is involved with each table, function, string etc..
* You can't easily get a bytecode listing of your ESP8266 code; however there are two broad options for doing this:
* **Generate a bytecode listing on your development PC**. The Lua 5.1 code generator is basically the same on the PC and on the ESP8266, so whilst it isn't identical, using the standard Lua batch compiler `luac` against your source on your PC with the `-l -s` option will give you a good idea of what your code will generate. The main difference between these two variants is the size_t for ESP8266 is 4 bytes rather than the 8 bytes size_t found on modern 64bit development PCs; and the eLua variants generate different access references for ROM data types. If you want to see what the `string.dump()` version generates then drop the `-s` option to retain the debug information.
* **Upload your `.lc` files to the PC and disassemble then there**. There are a number of Lua code disassemblers which can list off the compiled code that you application modules will generate, `if` you have a script to upload files from your ESP8266 to your development PC. I use [ChunkSpy](http://luaforge.net/projects/chunkspy/) which can be downloaded [here](http://files.luaforge.net/releases/chunkspy/chunkspy/ChunkSpy-0.9.8/ChunkSpy-0.9.8.zip) , but you will need to apply the following patch so that ChunkSpy understands eLua data types:
```diff
--- a/ChunkSpy-0.9.8/5.1/ChunkSpy.lua 2015-05-04 12:39:01.267975498 +0100
+++ b/ChunkSpy-0.9.8/5.1/ChunkSpy.lua 2015-05-04 12:35:59.623983095 +0100
@@ -2193,6 +2193,9 @@
config.AUTO_DETECT = true
elseif a == "--brief" then
config.DISPLAY_BRIEF = true
+ elseif a == "--elua" then
+ config.LUA_TNUMBER = 5
+ config.LUA_TSTRING = 6
elseif a == "--interact" then
perform = ChunkSpy_Interact
```
* Your other great friend is to use `node.heap()` regularly through your code.
* Use these tools and play with coding approaches to see how many instructions each typical line of code takes in your coding style. The Lua Wiki gives some general optimisation tips, but in general just remember that these focus on optimising for execution speed and you will be interested mainly in optimising for code and variable space as these are what consumes precious RAM.
### What is the cost of using functions?
Consider the output of `dofile("test1a.lua")` on the following code compared to the equivalent where the function `pnh()` is removed and the extra `print(heap())` statement is placed inline:
```lua
-- test1b.lua
collectgarbage()
local heap = node.heap
print(heap())
local function pnh() print(heap()) end
pnh()
print(heap())
```
|Heap Value | Function Call | Inline |
|-----------|---------------|--------|
| 1 | 20712 | 21064 |
| 2 | 20624 | 21024 |
| 3 | 20576 | 21024 |
Here bigger means less RAM used.
Of course you should still use functions to structure your code and encapsulate common repeated processing, but just bear in mind that each function definition has a relatively high overhead for its header record and stack frame (compared to the 20 odd KB RAM available). *So try to avoid overusing functions. If there are less than a dozen or so lines in the function then you should consider putting this code inline if it makes sense to do so.*
### What other resources are available?
* Install lua and luac on your development PC. This is freely available for Windows, Mac and Linux distributions, but we strongly suggest that you use Lua 5.1 to maintain source compatibility with ESP8266 code. This will allow you not only to unit test some modules on your PC in a rich development environment, but you can also use `luac` to generate a bytecode listing of your code and to validate new code syntactically before downloading to the ESP8266. This will also allow you to develop server-side applications and embedded applications in a common language.
## Firmware and Lua app development
### How to save memory?
* The NodeMCU development team recommends that you consider using a tailored firmware build, which only includes the modules that you plan to use before developing any Lua application. Once you have the ability to make and flash custom builds, the you also have the option of moving time sensitive or logic intensive code into your own custom module. Doing this can save a large amount of RAM as C code can be run directly from Flash memory. If you want an easy-to-use intermediate option then why note try the [cloud based NodeMCU custom build service](http://frightanic.com/NodeMCU-custom-build)?.
## Hardware Specifics
### Why file writes fail all the time on DEVKIT V1.0?
NodeMCU DEVKIT V1.0 uses ESP12-E-DIO(ESP-12-D) module. This module runs the Flash memory in [Dual IO SPI](#whats-the-different-between-dio-and-qio-mode) (DIO) mode. This firmware will not be correctly loaded if you uses old flashtool version, and the filesystem will not work if you used a pre 0.9.6 firmware version (<0.9.5) or old. The easiest way to resolve this problem s update all the firmware and flash tool to current version.
- Use the latest [esptool.py](https://github.com/themadinventor/esptool) with DIO support and command option to flash firmware, or
- Use the latest [NodeMCU flasher](https://github.com/NodeMCU/NodeMCU-flasher) with default option. (You must select the `restore to default` option in advanced menu tab), or
- Use the latest Espressif's flash tool -- see [this Espressif forum topic](http://bbs.espressif.com/viewtopic.php?f=5&t=433) (without auto download support). Use DIO mode and 32M flash size option, and flash latest firmware to 0x00000. Before flashing firmware, remember to hold FLASH button, and press RST button once. Note that the new NodeMCU our firmware download tool, when released, will be capable of flashing firmware automatically without any button presses.
### What's the different between DIO and QIO mode?
<TODO>
### How to use DEVKIT V0.9 on Mac OS X?
<TODO>
### How does DEVKIT use DTR and RTS enter download mode?
<TODO>
Adafruit provides a really nice [firmware flashing tutorial](https://learn.adafruit.com/building-and-running-micropython-on-the-esp8266/flash-firmware). Below you'll find just the basics for the two popular tools esptool and NodeMCU Flasher.
!!! note "Note:"
Keep in mind that the ESP8266 needs to be put into flash mode before you can flash a new firmware!
To enable ESP8266 firmware flashing GPIO0 pin must be pulled low before the device is reset. Conversely, for a normal boot, GPIO0 must be pulled high or floating.
If you have a [NodeMCU dev kit](https://github.com/nodemcu/nodemcu-devkit-v1.0) then you don't need to do anything, as the USB connection can pull GPIO0 low by asserting DTR and reset your board by asserting RTS.
If you have an ESP-01 or other device without built-in USB, you will need to enable flashing yourself by pulling GPIO0 low or pressing a "flash" switch.
## esptool
> A cute Python utility to communicate with the ROM bootloader in Espressif ESP8266. It is intended to be a simple, platform independent, open source replacement for XTCOM.
Source: [https://github.com/themadinventor/esptool](https://github.com/themadinventor/esptool)
Supported platforms: OS X, Linux, Windows, anything that runs Python
**Running esptool.py**
Run the following command to flash an *aggregated* binary as is produced for example by the [cloud build service](build.md#cloud-build-service) or the [Docker image](build.md#docker-image).
`esptool.py --port <USB-port-with-ESP8266> write_flash 0x00000 <nodemcu-firmware>.bin`
## NodeMCU Flasher
> A firmware Flash tool for NodeMCU...We are working on next version and will use QT framework. It will be cross platform and open-source.
Source: [https://github.com/nodemcu/nodemcu-flasher](https://github.com/nodemcu/nodemcu-flasher)
Supported platforms: Windows
\ No newline at end of file
# NodeMCU Documentation
NodeMCU is an [eLua](http://www.eluaproject.net/) based firmware for the [ESP8266 WiFi SOC from Espressif](http://espressif.com/en/products/esp8266/). The firmware is based on the Espressif NON-OS SDK and uses a file system based on [spiffs](https://github.com/pellepl/spiffs). The code repository consists of 98.1% C-code that glues the thin Lua veneer to the SDK.
The NodeMCU *firmware* is a companion project to the popular [NodeMCU dev kits](https://github.com/nodemcu/nodemcu-devkit-v1.0), ready-made open source development boards with ESP8266-12E chips.
## Programming Model
The NodeMCU programming model is similar to that of [Node.js](https://en.wikipedia.org/wiki/Node.js), only in Lua. It is asynchronous and event-driven. Many functions, therefore, have parameters for callback functions. To give you an idea what a NodeMCU program looks like study the short snippets below. For more extensive examples have a look at the `/lua_examples` folder in the repository on GitHub.
```lua
-- a simple HTTP server
srv = net.createServer(net.TCP)
srv:listen(80, function(conn)
conn:on("receive", function(conn, payload)
print(payload)
conn:send("<h1> Hello, NodeMCU.</h1>")
end)
conn:on("sent", function(conn) conn:close() end)
end)
```
```lua
-- connect to WiFi access point
wifi.setmode(wifi.STATION)
wifi.sta.config("SSID", "password")
```
```lua
-- register event callbacks for WiFi events
wifi.sta.eventMonReg(wifi.STA_CONNECTING, function(previous_state)
if(previous_state==wifi.STA_GOTIP) then
print("Station lost connection with access point. Attempting to reconnect...")
else
print("STATION_CONNECTING")
end
end)
```
```lua
-- manipulate hardware like with Arduino
pin = 1
gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, gpio.HIGH)
print(gpio.read(pin))
```
## Getting Started
1. [Build the firmeware](build.md) with the modules you need.
1. [Flash the firmware](flash.md) to the chip.
1. [Upload code](upload.md) to the firmware.
# ADC Module
The ADC module provides access to the in-built ADC.
On the ESP8266 there is only a single-channel, which is multiplexed with the battery voltage. Depending on the setting in the "esp init data" (byte 107) one can either use the ADC to read an external voltage, or to read the system voltage, but not both.
The default setting in the NodeMCU firmware can be controlled via user_config.h at compile time, by defining one of ESP_INIT_DATA_ENABLE_READVDD33, ESP_INIT_DATA_ENABLE_READADC or ESP_INIT_DATA_FIXED_VDD33_VALUE. To change the setting at a later date, use Espressif's flash download tool to create a new init data block.
## adc.read()
Samples the ADC.
####Syntax
`adc.read(channel)`
####Parameters
`channel` always 0 on the ESP8266
####Returns
the sampled value (number)
####Example
```lua
val = adc.read(0)
```
## adc.readvdd33()
Reads the system voltage.
####Syntax
`adc.readvdd33()`
####Parameters
none
####Returns
system voltage in millivolts (number)
If the ESP8266 has been configured to use the ADC for sampling the external pin, this function will always return 65535. This is a hardware and/or SDK limitation.
\ No newline at end of file
# bit Module
Bit manipulation support, on 32bit integers.
## bit.arshift()
Arithmetic right shift a number equivalent to `value >> shift` in C.
####Syntax
`bit.arshift(value, shift)`
####Parameters
- `value` the value to shift
- `shift` positions to shift
####Returns
the number shifted right (arithmetically)
## bit.band()
Bitwise AND, equivalent to `val1 & val2 & ... & valn` in C.
####Syntax
`bit.band(val1, val2 [, ... valn])`
####Parameters
- `val1` first AND argument
- `val2` second AND argument
- `...valn` ...nth AND argument
####Returns
the bitwise AND of all the arguments (number)
## bit.bit()
Generate a number with a 1 bit (used for mask generation). Equivalent to `1 << position` in C.
####Syntax
`bit.bit(position)`
####Parameters
`position` position of the bit that will be set to 1
####Returns
a number with only one 1 bit at position (the rest are set to 0)
## bit.bnot()
Bitwise negation, equivalent to `~value in C.
####Syntax
`bit.bnot(value)`
####Parameters
`value` the number to negate
####Returns
the bitwise negated value of the number
## bit.bor()
Bitwise OR, equivalent to `val1 | val2 | ... | valn` in C.
####Syntax
`bit.bor(val1, val2 [, ... valn])`
####Parameters
- `val1` first OR argument.
- `val2` second OR argument.
- `...valn` ...nth OR argument
####Returns
the bitwise OR of all the arguments (number)
## bit.bxor()
Bitwise XOR, equivalent to `val1 ^ val2 ^ ... ^ valn` in C.
####Syntax
`bit.bxor(val1, val2 [, ... valn])`
####Parameters
- `val1` first XOR argument
- `val2` second XOR argument
- `...valn` ...nth XOR argument
####Returns
the bitwise XOR of all the arguments (number)
## bit.clear()
Clear bits in a number.
####Syntax
`bit.clear(value, pos1 [, ... posn])`
####Parameters
- `value` the base number
- `pos1` position of the first bit to clear
- `...posn` position of thet nth bit to clear
####Returns
the number with the bit(s) cleared in the given position(s)
## bit.isclear()
Test if a given bit is cleared.
####Syntax
`bit.isclear(value, position)`
####Parameters
- `value` the value to test
- `position` bit position to test
####Returns
true if the bit at the given position is 0, false othewise
## bit.isset()
Test if a given bit is set.
####Syntax
`bit.isset(value, position)`
####Parameters
- `value` the value to test
- `position` bit position to test
####Returns
true if the bit at the given position is 1, false otherwise
## bit.lshift()
Left-shift a number, equivalent to `value << shift` in C.
####Syntax
`bit.lshift(value, shift)`
####Parameters
- `value` the value to shift
- `shift` positions to shift
####Returns
the number shifted left
## bit.rshift()
Logical right shift a number, equivalent to `( unsigned )value >> shift` in C.
####Syntax
`bit.rshift(value, shift)`
####Parameters
- `value` the value to shift.
- `shift` positions to shift.
####Returns
the number shifted right (logically)
## bit.set()
Set bits in a number.
####Syntax
`bit.set(value, pos1 [, ... posn ])`
####Parameters
- `value` the base number.
- `pos1` position of the first bit to set.
- `...posn` position of the nth bit to set.
####Returns
the number with the bit(s) set in the given position(s)
\ No newline at end of file
# BMP085 Module
This module provides access to the [BMP085](https://www.sparkfun.com/tutorials/253) temperature and pressure sensor. The module also works with BMP180.
## bmp085.init()
Initializes the module and sets the pin configuration.
#### Syntax
`bmp085.init(sda, scl)`
#### Parameters
- `sda` data pin
- `scl` clock pin
#### Returns
`nil`
## bmp085.temperature()
Samples the sensor and returns the temperature in celsius as an integer multiplied with 10.
#### Syntax
`bmp085.temperature()`
#### Returns
temperature multiplied with 10 (integer)
#### Example
```lua
bmp085.init(1, 2)
local t = bmp085.temperature()
print(string.format("Temperature: %s.%s degrees C", t / 10, t % 10))
```
## bmp085.pressure()
Samples the sensor and returns the pressure in pascal as an integer.
The optional `oversampling_setting` parameter determines for how long time the sensor samples data.
The default is `3` which is the longest sampling setting. Possible values are 0, 1, 2, 3.
See the data sheet for more information.
#### Syntax
`bmp085.pressure(oversampling_setting)`
#### Parameters
`oversampling_setting` integer that can be 0, 1, 2 or 3
#### Returns
pressure in pascals (integer)
#### Example
```lua
bmp085.init(1, 2)
local p = bmp085.pressure()
print(string.format("Pressure: %s.%s mbar", p / 100, p % 100))
```
## bmp085.pressure_raw()
Samples the sensor and returns the raw pressure in internal units. Might be useful if you need higher precision.
#### Syntax
`bmp085.pressure_raw(oversampling_setting)`
#### Parameters
`oversampling_setting` integer that can be 0, 1, 2 or 3
#### Returns
raw pressure sampling value (integer)
# CJSON Module
The JSON support module. Allows encoding and decoding to/from JSON.
Please note that nested tables can require a lot of memory to encode. To catch out-of-memory errors, use `pcall()`.
## cjson.encode()
Encode a Lua table to a JSON string. For details see the [documentation of the original Lua library](http://kyne.com.au/~mark/software/lua-cjson-manual.html#encode).
####Syntax
`cjson.encode(table)`
####Parameters
`table` data to encode
While it also is possible to encode plain strings and numbers rather than a table, it is not particularly useful to do so.
####Returns
JSON string
####Example
```lua
ok, json = pcall(cjson.encode, {key="value"})
if ok then
print(json)
else
print("failed to encode!")
end
```
## cjson.decode()
Decode a JSON string to a Lua table. For details see the [documentation of the original Lua library](http://kyne.com.au/~mark/software/lua-cjson-manual.html#_decode).
####Syntax
`cjson.decode(str)`
####Parameters
`str` JSON string to decode
####Returns
Lua table representation of the JSON data
####Example
```lua
t = cjson.decode('{"key":"value"}')
for k,v in pairs(t) do print(k,v) end
```
\ No newline at end of file
# CoAP Module
The CoAP module provides a simple implementation according to [CoAP](http://tools.ietf.org/html/rfc7252) protocol.
The basic endpoint server part is based on [microcoap](https://github.com/1248/microcoap), and many other code reference [libcoap](https://github.com/obgm/libcoap).
This module implements both the client and the server side. GET/PUT/POST/DELETE is partially supported by the client. Server can register Lua functions and varibles. No observe or discover supported yet.
## Caution
This module is only in the very early stage and not complete yet.
## Constants
Constants for various functions.
`coap.CON`, `coap.NON` represent the request types.
`coap.TEXT_PLAIN`, `coap.LINKFORMAT`, `coap.XML`, `coap.OCTET_STREAM`, `coap.EXI`, `coap.JSON` represent content types.
## coap.Client()
Creates a CoAP client.
#### Syntax
`coap.Client()`
#### Parameters
none
#### Returns
CoAP client
#### Example
```lua
cc = coap.Client()
-- assume there is a coap server at ip 192.168.100
cc:get(coap.CON, "coap://192.168.18.100:5683/.well-known/core")
-- GET is not complete, the result/payload only print out in console.
cc:post(coap.NON, "coap://192.168.18.100:5683/", "Hello")
```
## coap.Server()
Creates a CoAP server.
#### Syntax
`coap.Server()`
#### Parameters
none
#### Returns
CoAP server
#### Example
```lua
-- use copper addon for firefox
cs=coap.Server()
cs:listen(5683)
myvar=1
cs:var("myvar") -- get coap://192.168.18.103:5683/v1/v/myvar will return the value of myvar: 1
all='[1,2,3]'
cs:var("all", coap.JSON) -- sets content type to json
-- function should tack one string, return one string.
function myfun(payload)
print("myfun called")
respond = "hello"
return respond
end
cs:func("myfun") -- post coap://192.168.18.103:5683/v1/f/myfun will call myfun
```
# CoAP Client
## coap.client:get()
Issues a GET request to the server.
#### Syntax
`coap.client:get(type, uri[, payload])`
#### Parameters
- `type` `coap.CON`, `coap.NON`, defaults to CON. If the type is CON and request fails, the library retries four more times before giving up.
- `uri` the URI such as "coap://192.168.18.103:5683/v1/v/myvar", only IP addresses are supported i.e. no hostname resoltion.
- `payload` optional, the payload will be put in the payload section of the request.
#### Returns
`nil`
## coap.client:put()
Issues a PUT request to the server.
#### Syntax
`coap.client:put(type, uri[, payload])`
#### Parameters
- `type` `coap.CON`, `coap.NON`, defaults to CON. If the type is CON and request fails, the library retries four more times before giving up.
- `uri` the URI such as "coap://192.168.18.103:5683/v1/v/myvar", only IP addresses are supported i.e. no hostname resoltion.
- `payload` optional, the payload will be put in the payload section of the request.
#### Returns
`nil`
## coap.client:post()
Issues a POST request to the server.
#### Syntax
`coap.client:post(type, uri[, payload])`
#### Parameters
- `type` coap.CON, coap.NON, defaults to CON. when type is CON, and request failed, the request will retry another 4 times before giving up.
- `uri` the uri such as coap://192.168.18.103:5683/v1/v/myvar, only IP is supported.
- `payload` optional, the payload will be put in the payload section of the request.
#### Returns
`nil`
## coap.client:delete()
Issues a DELETE request to the server.
#### Syntax
`coap.client:delete(type, uri[, payload])`
#### Parameters
- `type` `coap.CON`, `coap.NON`, defaults to CON. If the type is CON and request fails, the library retries four more times before giving up.
- `uri` the URI such as "coap://192.168.18.103:5683/v1/v/myvar", only IP addresses are supported i.e. no hostname resoltion.
- `payload` optional, the payload will be put in the payload section of the request.
#### Returns
`nil`
# CoAP Server
## coap.server:listen()
Starts the CoAP server on the given port.
#### Syntax
`coap.server:listen(port[, ip])`
#### Parameters
- `port` server port (number)
- `ip` optional IP address
#### Returns
`nil`
## coap.server:close()
Closes the CoAP server.
#### Syntax
`coap.server:close()`
#### Parameters
none
#### Returns
`nil`
## coap.server:var()
Registers a Lua variable as an endpoint in the server. the variable value then can be retrieved by a client via GET method, represented as an [URI](http://tools.ietf.org/html/rfc7252#section-6) to the client. The endpoint path for varialble is '/v1/v/'.
#### Syntax
`coap.server:var(name[, content_type])`
#### Parameters
- `name` the Lua variable's name
- `content_type` optional, defaults to `coap.TEXT_PLAIN`, see [Content Negotiation](http://tools.ietf.org/html/rfc7252#section-5.5.4)
#### Returns
`nil`
#### Example
```lua
-- use copper addon for firefox
cs=coap.Server()
cs:listen(5683)
myvar=1
cs:var("myvar") -- get coap://192.168.18.103:5683/v1/v/myvar will return the value of myvar: 1
-- cs:var(myvar), WRONG, this api accept the name string of the varialbe. but not the variable itself.
all='[1,2,3]'
cs:var("all", coap.JSON) -- sets content type to json
```
## coap.server:func()
Registers a Lua function as an endpoint in the server. The function then can be called by a client via POST method. represented as an [URI](http://tools.ietf.org/html/rfc7252#section-6) to the client. The endpoint path for function is '/v1/f/'.
When the client issues a POST request to this URI, the payload will be passed to the function as parameter. The function's return value will be the payload in the message to the client.
The function registered SHOULD accept ONLY ONE string type parameter, and return ONE string value or return nothing.
#### Syntax
`coap.server:func(name[, content_type])`
#### Parameters
- `name` the Lua function's name
- `content_type` optional, defaults to `coap.TEXT_PLAIN`, see [Content Negotiation](http://tools.ietf.org/html/rfc7252#section-5.5.4)
#### Returns
`nil`
#### Example
```lua
-- use copper addon for firefox
cs=coap.Server()
cs:listen(5683)
-- function should take only one string, return one string.
function myfun(payload)
print("myfun called")
respond = "hello"
return respond
end
cs:func("myfun") -- post coap://192.168.18.103:5683/v1/f/myfun will call myfun
-- cs:func(myfun), WRONG, this api accept the name string of the function. but not the function itself.
```
# crypto Module
The crypto modules provides various functions for working with cryptographic algorithms.
## crypto.hash()
Compute a cryptographic hash of a Lua string.
#### Syntax
`hash = crypto.hash(algo, str)`
#### Parameters
`algo` the hash algorithm to use, case insensitive string
Supported hash algorithms are:
- MD2 (not available by default, has to be explicitly enabled in `app/include/user_config.h`)
- MD5
- SHA1
- SHA256, SHA384, SHA512 (unless disabled in `app/include/user_config.h`)
#### Returns
A binary string containing the message digest. To obtain the textual version (ASCII hex characters), please use [`crypto.toHex()`](#cryptotohex ).
#### Example
```lua
print(crypto.toHex(crypto.hash("sha1","abc")))
```
## crypto.hmac()
Compute a [HMAC](https://en.wikipedia.org/wiki/Hash-based_message_authentication_code) (Hashed Message Authentication Code) signature for a Lua string.
#### Syntax
`signature = crypto.hmac(algo, str, key)`
#### Parameters
- `algo` hash algorithm to use, case insensitive string
- `str` data to calculate the hash for
- `key` key to use for signing, may be a binary string
Supported hash algorithms are:
- MD2 (not available by default, has to be explicitly enabled in `app/include/user_config.h`)
- MD5
- SHA1
- SHA256, SHA384, SHA512 (unless disabled in `app/include/user_config.h`)
#### Returns
A binary string containing the HMAC signature. Use [`crypto.toHex()`](#cryptotohex ) to obtain the textual version.
#### Example
```lua
print(crypto.toHex(crypto.hmac("sha1","abc","mysecret")))
```
## crypto.mask()
Applies an XOR mask to a Lua string. Note that this is not a proper cryptographic mechanism, but some protocols may use it nevertheless.
#### Syntax
`crypto.mask(message, mask)`
#### Parameters
- `message` message to mask
- `mask` the mask to apply, repeated if shorter than the message
#### Returns
The masked message, as a binary string. Use [`crypto.toHex()`](#cryptotohex) to get a textual representation of it.
#### Example
```lua
print(crypto.toHex(crypto.mask("some message to obscure","X0Y7")))
```
## crypto.toBase64()
Provides a Base64 representation of a (binary) Lua string.
#### Syntax
`b64 = crypto.toBase64(binary)`
#### Parameters
`binary` input string to Base64 encode
#### Return
A Base64 encoded string.
#### Example
```lua
print(crypto.toBase64(crypto.hash("sha1","abc")))
```
## crypto.toHex()
Provides an ASCII hex representation of a (binary) Lua string. Each byte in the input string is represented as two hex characters in the output.
#### Syntax
`hexstr = crypto.toHex(binary)`
#### Parameters
`binary` input string to get hex representation for
#### Returns
An ASCII hex string.
#### Example
```lua
print(crypto.toHex(crypto.hash("sha1","abc")))
```
# dht Module
## Constants
`dht.OK` (0), `dht.ERROR_CHECKSUM` (1), `dht.ERROR_TIMEOUT` (2)
## dht.read()
Read all kinds of DHT sensors, including DHT11, 21, 22, 33, 44 humidity temperature combo sensor.
#### Syntax
`dht.read(pin)`
#### Parameters
`pin` pin number of DHT sensor (can't be 0), type is number
#### Returns
- `status` as defined in Constants
- `temp` temperature (see note below)
- `humi` humidity (see note below)
- `temp_dec` temperature decimal
- `humi_dec` humidity decimal
!!! note "Note:"
If using float firmware then `temp` and `humi` are floating point numbers. On an integer firmware, the final values have to be concatenated from `temp` and `temp_dec` / `humi` and `hum_dec`.
#### Example
```lua
pin = 5
status, temp, humi, temp_dec, humi_dec = dht.read(pin)
if status == dht.OK then
-- Integer firmware using this example
print(string.format("DHT Temperature:%d.%03d;Humidity:%d.%03d\r\n",
math.floor(temp),
temp_deci,
math.floor(humi),
humi_deci
))
-- Float firmware using this example
print("DHT Temperature:"..temp..";".."Humidity:"..humi)
elseif status == dht.ERROR_CHECKSUM then
print( "DHT Checksum error." )
elseif status == dht.ERROR_TIMEOUT then
print( "DHT timed out." )
end
```
## dht.read11()
Read DHT11 humidity temperature combo sensor.
#### Syntax
`dht.read11(pin)`
#### Parameters
`pin` pin number of DHT11 sensor (can't be 0), type is number
#### Returns
- `status` as defined in Constants
- `temp` temperature (see note below)
- `humi` humidity (see note below)
- `temp_dec` temperature decimal
- `humi_dec` humidity decimal
!!! note "Note:"
If using float firmware then `temp` and `humi` are floating point numbers. On an integer firmware, the final values have to be concatenated from `temp` and `temp_dec` / `humi` and `hum_dec`.
#### See also
[dht.read()](#dhtread)
## dht.readxx()
Read all kinds of DHT sensors, except DHT11.
####Syntax
`dht.readxx(pin)`
#### Parameters
`pin` pin number of DHT sensor (can't be 0), type is number
#### Returns
- `status` as defined in Constants
- `temp` temperature (see note below)
- `humi` humidity (see note below)
- `temp_dec` temperature decimal
- `humi_dec` humidity decimal
!!! note "Note:"
If using float firmware then `temp` and `humi` are floating point numbers. On an integer firmware, the final values have to be concatenated from `temp` and `temp_dec` / `humi` and `hum_dec`.
#### See also
[dht.read()](#dhtread)
# enduser setup Module
This module provides a simple way of configuring ESP8266 chips without using a serial interface or pre-programming WiFi credentials onto the chip.
![enduser setup config dialog](../../img/enduser-setup.jpg "enduser setup config dialog")
After running [`enduser_setup.start()`](#enduser_setupstart) a portal like the above can be accessed through a wireless network called SetupGadget_XXXXXX. The portal is used to submit the credentials for the WiFi of the enduser.
After an IP address has been successfully obtained this module will stop as if [`enduser_setup.stop()`](#enduser_setupstop) had been called.
## enduser_setup.start()
Starts the captive portal.
#### Syntax
`enduser_setup.start([onConfigured()], [onError(err_num, string)], [onDebug(string)])`
#### Parameters
- `onConfigured()` callback will be fired when an IP-address has been obtained, just before the enduser_setup module will terminate itself
- `onError()` callback will be fired if an error is encountered. `err_num` is a number describing the error, and `string` contains a description of the error.
- `onDebug()` callback is disabled by default. It is intended to be used to find internal issues in the module. `string` contains a description of what is going on.
#### Returns
`nil`
#### Example
```lua
enduser_setup.start(
function()
print("Connected to wifi as:" .. wifi.sta.getip())
end,
function(err, str)
print("enduser_setup: Err #" .. err .. ": " .. str)
end
);
```
## enduser_setup.stop()
Stops the captive portal.
#### Syntax
`enduser_setup.stop()`
#### Parameters
none
#### Returns
`nil`
\ No newline at end of file
# file Module
The file module provides access to the file system and its individual files.
The file system is a flat file system, with no notion of directories/folders.
Only one file can be open at any given time.
## file.close()
Closes the open file, if any.
#### Syntax
`file.close()`
#### Parameters
none
#### Returns
`nil`
#### Example
```lua
-- open 'init.lua', print the first line.
file.open("init.lua", "r")
print(file.readline())
file.close()
```
#### See also
[`file.open()`](#fileopen)
## file.flush()
Flushes any pending writes to the file system, ensuring no data is lost on a restart. Closing the open file using [`file.close()`](#fileclose) performs an implicit flush as well.
#### Syntax
`file.flush()`
#### Parameters
none
#### Returns
`nil`
#### Example
```lua
-- open 'init.lua' in 'a+' mode
file.open("init.lua", "a+")
-- write 'foo bar' to the end of the file
file.write('foo bar')
file.flush()
-- write 'baz' too
file.write('baz')
file.close()
```
#### See also
[`file.close()`](#fileclose)
## file.format()
Format the file system. Completely erases any existing file system and writes a new one. Depending on the size of the flash chip in the ESP, this may take several seconds.
#### Syntax
`file.format()`
#### Parameters
none
#### Returns
`nil`
#### See also
[`file.remove()`](#fileremove)
## file.fsinfo()
Return size information for the file system, in bytes.
#### Syntax
`file.fsinfo()`
#### Parameters
none
#### Returns
- `remaining` (number)
- `used` (number)
- `total` (number)
#### Example
```lua
-- get file system info
remaining, used, total=file.fsinfo()
print("\nFile system info:\nTotal : "..total.." Bytes\nUsed : "..used.." Bytes\nRemain: "..remaining.." Bytes\n")
```
## file.list()
Lists all files in the file system.
#### Syntax
`file.list()`
#### Parameters
none
#### Returns
a lua table which contains the {file name: file size} pairs
#### Example
```lua
l = file.list();
for k,v in pairs(l) do
print("name:"..k..", size:"..v)
end
```
## file.open()
Opens a file for access, potentially creating it (for write modes).
When done with the file, it must be closed using `file.close()`.
#### Syntax
`file.open(filename, mode)`
#### Parameters
- `filename` file to be opened, directories are not supported
- `mode`:
- "r": read mode (the default)
- "w": write mode
- "a": append mode
- "r+": update mode, all previous data is preserved
- "w+": update mode, all previous data is erased
- "a+": append update mode, previous data is preserved, writing is only allowed at the end of file
#### Returns
`nil` if file not opened, or not exists (read modes). `true` if file opened ok.
#### Example
```lua
-- open 'init.lua', print the first line.
file.open("init.lua", "r")
print(file.readline())
file.close()
```
#### See also
- [`file.close()`](#fileclose)
- [`file.readline()`](#filereadline)
## file.read()
Read content from the open file.
#### Syntax
`file.read([n_or_str])`
#### Parameters
- `n_or_str`:
- if nothing passed in, read all byte in file
- if pass a number n, then read n bytes from file, or EOF is reached
- if pass a string "str", then read until 'str' or EOF is reached
#### Returns
fdile content in string, or nil when EOF
#### Example
```lua
-- print the first line of 'init.lua'
file.open("init.lua", "r")
print(file.read('\n'))
file.close()
-- print the first 5 byte of 'init.lua'
file.open("init.lua", "r")
print(file.read(5))
file.close()
```
#### See also
- [`file.open()`](#fileopen)
- [`file.readline()`](#filereadline)
## file.readline()
Read the next line from the open file.
#### Syntax
`file.readline()`
#### Parameters
none
#### Returns
File content in string, line by line, include EOL('\n'). Return `nil` when EOF.
#### Example
```lua
-- print the first line of 'init.lua'
file.open("init.lua", "r")
print(file.readline())
file.close()
```
#### See also
- [`file.open()`](#fileopen)
- [`file.close()`](#fileclose)
- [`file.read()`](#filereade)
## file.remove()
Remove a file from the file system. The file must not be currently open.
###Syntax
`file.remove(filename)`
#### Parameters
`filename` file to remove
#### Returns
`nil`
#### Example
```lua
-- remove "foo.lua" from file system.
file.remove("foo.lua")
```
#### See also
[`file.open()`](#fileopen)
## file.rename()
Renames a file. If a file is currently open, it will be closed first.
#### Syntax
`file.rename(oldname, newname)`
#### Parameters
- `oldname` old file name
- `newname` new file name
#### Returns
`true` on success, `false` on error.
#### Example
```lua
-- rename file 'temp.lua' to 'init.lua'.
file.rename("temp.lua","init.lua")
```
## file.seek()
Sets and gets the file position, measured from the beginning of the file, to the position given by offset plus a base specified by the string whence.
#### Syntax
`file.seek([whence [, offset]])`
#### Parameters
- `whence`
- "set": base is position 0 (beginning of the file)
- "cur": base is current position (default value)
- "end": base is end of file
- `offset` default 0
If no parameters are given, the function simply returns the current file offset.
#### Returns
the resulting file position, or `nil` on error
#### Example
```lua
file.open("init.lua", "r")
-- skip the first 5 bytes of the file
file.seek("set", 5)
print(file.readline())
file.close()
```
#### See also
[`file.open()`](#fileopen)
## file.write()
Write a string to the open file.
#### Syntax
`file.write(string)`
#### Parameters
`string` content to be write to file
#### Returns
`true` if the write is ok, `nil` on error
#### Example
```lua
-- open 'init.lua' in 'a+' mode
file.open("init.lua", "a+")
-- write 'foo bar' to the end of the file
file.write('foo bar')
file.close()
```
#### See also
- [`file.open()`](#fileopen)
- [`file.writeline()`](#filewriteline)
## file.writeline()
Write a string to the open file and append '\n' at the end.
#### Syntax
`file.writeline(string)`
#### Parameters
`string` content to be write to file
#### Returns
`true` if write ok, `nil` on error
#### Example
```lua
-- open 'init.lua' in 'a+' mode
file.open("init.lua", "a+")
-- write 'foo bar' to the end of the file
file.writeline('foo bar')
file.close()
```
#### See also
- [`file.open()`](#fileopen)
- [`file.readline()`](#filereadline)
\ No newline at end of file
# GPIO Module
This module provides access to the [GPIO](https://en.wikipedia.org/wiki/General-purpose_input/output) (General Purpose Input/Output) subsystem.
All access is based on the I/O index number on the NodeMCU dev kits, not the internal GPIO pin. For example, the D0 pin on the dev kit is mapped to the internal GPIO pin 16.
If not using a NodeMCU dev kit, please refer to the below GPIO pin maps for the index↔gpio mapping.
| IO index | ESP8266 pin | IO index | ESP8266 pin |
|---------:|:------------|---------:|:------------|
| 0 [*] | GPIO16 | 7 | GPIO13 |
| 1 | GPIO5 | 8 | GPIO15 |
| 2 | GPIO4 | 9 | GPIO3 |
| 3 | GPIO0 | 10 | GPIO1 |
| 4 | GPIO2 | 11 | GPIO9 |
| 5 | GPIO14 | 12 | GPIO10 |
| 6 | GPIO12 | | |
** [*] D0(GPIO16) can only be used as gpio read/write. No interrupt support. No pwm/i2c/ow support. **
## gpio.mode()
Initialize pin to GPIO mode, set the pin in/out direction, and optional internal pullup.
#### Syntax
`gpio.mode(pin, mode [, pullup])`
#### Parameters
- `pin` pin to configure, IO index
- `mode` one of gpio.OUTPUT or gpio.INPUT, or gpio.INT(interrupt mode)
- `pullup` gpio.PULLUP or gpio.FLOAT; default is gpio.FLOAT
#### Returns
`nil`
#### Example
```lua
gpio.mode(0, gpio.OUTPUT)
```
#### See also
- [`gpio.read()`](#gpioread)
- [`gpio.write()`](#gpiowrite)
## gpio.read()
Read digital GPIO pin value.
#### Syntax
`gpio.read(pin)`
#### Parameters
`pin` pin to read, IO index
#### Returns
a number, 0 = low, 1 = high
#### Example
```lua
-- read value of gpio 0.
gpio.read(0)
```
#### See also
[`gpio.mode()`](#gpiomode)
## gpio.serout()
Serialize output based on a sequence of delay-times. After each delay, the pin is toggled.
#### Syntax
`gpio.serout(pin, start_level, delay_times [, repeat_num])`
#### Parameters
- `pin` pin to use, IO index
- `start_level` level to start on, either `gpio.HIGH` or `gpio.LOW`
- `delay_times` an array of delay times between each toggle of the gpio pin.
- `repeat_num` an optional number of times to run through the sequence.
Note that this function blocks, and as such any use of it must adhere to the SDK guidelines of time spent blocking the stack (10-100ms). Failure to do so may lead to WiFi issues or outright crashes/reboots.
#### Returns
`nil`
#### Example
```lua
gpio.mode(1,gpio.OUTPUT,gpio.PULLUP)
gpio.serout(1,1,{30,30,60,60,30,30}) -- serial one byte, b10110010
gpio.serout(1,1,{30,70},8) -- serial 30% pwm 10k, lasts 8 cycles
gpio.serout(1,1,{3,7},8) -- serial 30% pwm 100k, lasts 8 cycles
gpio.serout(1,1,{0,0},8) -- serial 50% pwm as fast as possible, lasts 8 cycles
gpio.serout(1,0,{20,10,10,20,10,10,10,100}) -- sim uart one byte 0x5A at about 100kbps
gpio.serout(1,1,{8,18},8) -- serial 30% pwm 38k, lasts 8 cycles
```
## gpio.trig()
Establish a callback function to run on interrupt for a pin.
There is currently no support for unregistering the callback.
This function is not available if GPIO_INTERRUPT_ENABLE was undefined at compile time.
#### Syntax
`gpio.trig(pin, type [, function(level)])`
#### Parameters
- `pin` **1~12**, IO index, pin D0 does not support interrupt.
- `type` "up", "down", "both", "low", "high", which represent rising edge, falling edge, both edge, low level, high level trig mode correspondingly.
- `function(level)` callback function when triggered. The gpio level is the param. Use previous callback function if undefined here.
#### Returns
`nil`
#### Example
```lua
-- use pin 1 as the input pulse width counter
pin = 1
pulse1 = 0
du = 0
gpio.mode(pin,gpio.INT)
function pin1cb(level)
du = tmr.now() - pulse1
print(du)
pulse1 = tmr.now()
if level == gpio.HIGH then gpio.trig(pin, "down") else gpio.trig(pin, "up") end
end
gpio.trig(pin, "down", pin1cb)
```
#### See also
[`gpio.mode()`](#gpiomode)
## gpio.write ()
Set digital GPIO pin value.
#### Syntax
`gpio.write(pin, level)`
#### Parameters
- `pin` pin to write, IO index
- `level` `gpio.HIGH` or `gpio.LOW`
#### Returns
`nil`
#### Example
```lua
-- set pin index 1 to GPIO mode, and set the pin to high.
pin=1
gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, gpio.HIGH)
```
#### See also
- [`gpio.mode()`](#gpiomode)
- [`gpio.read()`](#gpioread)
\ No newline at end of file
# HTTP Module
Basic HTTP client module.
Provides an interface to do basic GET/POST/PUT/DELETE over HTTP(S), as well as customized requests. Due to the memory constraints on ESP8266, the supported page/body size is limited to 1k. Attempting to receive pages larger than this limit will fail. If larger page/body sizes are necessary, consider using `net.createConnection()` and stream in the data.
Each request method takes a callback which is invoked when the response has been received from the server. The first argument is the status code, which is either a regular HTTP status code, or -1 to denote a DNS, connection or out-of-memory failure, or a timeout (currently at 10 seconds).
For each operation it is also possible to include custom headers. Note that following headers *can not* be overridden however:
- Host
- Connection
- User-Agent
The `Host` header is taken from the URL itself, the `Connection` is always set to `close`, and the `User-Agent` is `ESP8266`.
Note that it is not possible to execute concurrent HTTP requests using this module. Starting a new request before the previous has completed will result in undefined behaviour.
#### See also
- [`net.createConnection()`](#netcreateconnection)
## http.delete()
Executes a HTTP delete request.
#### Syntax
`http.delete(url, headers, body, callback)`
#### Parameters
- `url` The URL to fetch, including the `http://` or `https://` prefix
- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
- `body` The body to post; must already be encoded in the appropriate format, but may be empty
- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
#### Returns
`nil`
#### Example
```lua
http.delete('https://connor.example.com/john',
"",
"",
function(code, data)
if (code < 0)
print("HTTP request failed")
else
print(code, data)
end
end)
```
## http.get()
Executes a HTTP GET request.
#### Syntax
`http.get(url, headers, callback)`
#### Parameters
- `url` The URL to fetch, including the `http://` or `https://` prefix
- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
#### Returns
`nil`
#### Example
```lua
http.get("https://www.vowstar.com/nodemcu/", nil, function(code, data)
if (code < 0)
print("HTTP request failed")
else
print(code, data)
end
end)
```
## http.post()
Executes a HTTP POST request.
#### Syntax
`http.post(url, headers, body, callback)`
#### Parameters
- `url` The URL to fetch, including the `http://` or `https://` prefix
- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
- `body` The body to post; must already be encoded in the appropriate format, but may be empty
- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
#### Returns
`nil`
#### Example
```lua
http.post('http://json.example.com/something',
'Content-Type: application/json\r\n',
'{"hello":"world"}',
function(code, data)
if (code < 0)
print("HTTP request failed")
else
print(code, data)
end
end)
```
## http.put()
Executes a HTTP PUT request.
#### Syntax
`http.put(url, headers, body, callback)`
#### Parameters
- `url` The URL to fetch, including the `http://` or `https://` prefix
- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
- `body` The body to post; must already be encoded in the appropriate format, but may be empty
- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
#### Returns
`nil`
#### Example
```lua
http.put('http://db.example.com/items.php?key=deckard',
'Content-Type: text/plain\r\n',
'Hello!\nStay a while, and listen...\n',
function(code, data)
if (code < 0)
print("HTTP request failed")
else
print(code, data)
end
end)
```
## http.request()
Execute a custom HTTP request for any HTTP method.
#### Syntax
`http.request(url, method, headers, body, callback)`
#### Parameters
- `url` The URL to fetch, including the `http://` or `https://` prefix
- `method` The HTTP method to use, e.g. "GET", "HEAD", "OPTIONS" etc
- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
- `body` The body to post; must already be encoded in the appropriate format, but may be empty
- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
#### Returns
`nil`
#### Example
```lua
http.request("https://www.example.com", "HEAD", "", "", function(code, data)
function(code, data)
if (code < 0)
print("HTTP request failed")
else
print(code, data)
end
end)
```
# HX711 Module
This module provides access to an [HX711 load cell amplifier/ADC](https://learn.sparkfun.com/tutorials/load-cell-amplifier-hx711-breakout-hookup-guide). The HX711 is an inexpensive 24bit ADC with programmable 128x, 64x, and 32x gain. Currently only channel A at 128x gain is supported.
Note: To save ROM image space, this module is not compiled into the firmware by default.
## hx711.init()
Initialize io pins for hx711 clock and data.
#### Syntax
`hx711.init(clk, data)`
#### Parameters
- `clk` pin the hx711 clock signal is connected to
- `data` pin the hx711 data signal is connected to
#### Returns
`nil`
#### Example
```lua
-- Initialize the hx711 with clk on pin 5 and data on pin 6
hx711.init(5,6)
```
## hx711.read()
Read digital loadcell ADC value.
#### Syntax
`hx711.read(mode)`
#### Parameters
`mode` ADC mode. This parameter is currently ignored and reserved to ensure backward compatability if support for additional modes is added. Currently only channel A @ 128 gain is supported.
|mode | channel | gain |
|-----|---------|------|
| 0 | A | 128 |
#### Returns
a number (24 bit signed ADC value extended to the machine int size)
#### Example
```lua
-- Read ch A with 128 gain.
raw_data = hx711.read(0)
```
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