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 by available memory. Attempting to receive pages larger than this will fail. If larger page/body sizes are necessary, consider using `net.createConnection()` and stream in the data.
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 by available memory. Attempting to receive pages larger than this will fail. If larger page/body sizes are necessary, consider using [`net.createConnection()`](#netcreateconnection) 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).
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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)
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 behavior.
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.
[Multicast DNS](https://en.wikipedia.org/wiki/Multicast_DNS) is used as part of Bonjour / Zeroconf. This allows system to identify themselves and the services that they provide on a local area network. Clients are then able to discover these systems and connect to them.
The client adheres to version 3.1.1 of the [MQTT](https://en.wikipedia.org/wiki/MQTT) protocol. Make sure that your broker supports and is correctly configured for version 3.1.1. The client is backwards incompatible with brokers running MQTT 3.1.
This module provides simple performance measurement for an application.
It samples the program counter roughly every 50 microseconds and builds
a histogram of the values that it finds. Since there is only a small amount
of memory to store the histogram, the user can specify which area of code
is of interest. The default is the enitre flash which contains code. Once the hotspots are
identified, then the run can then be repeated with different areas and at different
resolutions to get as much information as required.
This module provides simple performance measurement for an application. It samples the program counter roughly every 50 microseconds and builds a histogram of the values that it finds. Since there is only a small amount
of memory to store the histogram, the user can specify which area of code is of interest. The default is the entire flash which contains code. Once the hotspots are identified, then the run can then be repeated with different areas and at different resolutions to get as much information as required.
This module can read the state of cheap rotary encoder switches. These are available at
all the standard places for a dollar or two. They are five pin devices where three are used
for a gray code encoder for rotation, and two are used for the push switch. These switches
are commonly used in car audio systems.
These switches do not have absolute positioning, but only encode the number of positions
rotated clockwise / anticlockwise. To make use of this module, connect the common pin on the quadrature
encoder to ground and the A and B phases to the nodemcu. One pin of the push switch should
also be grounded and the other pin connected to the nodemcu.
This module can read the state of cheap rotary encoder switches. These are available at all the standard places for a dollar or two. They are five pin devices where three are used for a gray code encoder for rotation, and two are used for the push switch. These switches are commonly used in car audio systems.
These switches do not have absolute positioning, but only encode the number of positions rotated clockwise / anti-clockwise. To make use of this module, connect the common pin on the quadrature encoder to ground and the A and B phases to the NodeMCU. One pin of the push switch should also be grounded and the other pin connected to the NodeMCU.
The rtcfifo module implements a first-in,first-out storage intended for sensor readings. As the name suggests, it is backed by the [RTC](https://en.wikipedia.org/wiki/Real-time_clock) user memory and as such survives deep sleep cycles. Conceptually it can be thought of as a cyclic array of `{ timestamp, name, value }` tuples. Internally it uses a space-optimized storage format to allow the greatest number of samples to be kept. This comes with several trade-offs, and as such is not a one-solution-fits-all. Notably:
The rtcmem module provides basic access to the [RTC](https://en.wikipedia.org/wiki/Real-time_clock)(Real Time Clock) memory.
The RTC in the ESP8266 contains memory registers which survive a deep sleep, making them highly useful for keeping state across sleep cycles. Some of this memory is reserved for system use, but 128 slots (each 32bit wide) are available for application use. This module provides read and write access to these.
The rtctime module provides advanced timekeeping support for NodeMCU, including keeping time across deep sleep cycles (provided [`rtctime.dsleep()`](#rtctimedsleep) is used instead of [`node.dsleep()`](node.md#nodedsleep)). This can be used to significantly extend battery life on battery powered sensor nodes, as it is no longer necessary to fire up the RF module each wake-up in order to obtain an accurate timestamp.