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ruanhaishen
Nodemcu Firmware
Commits
04ed036c
Commit
04ed036c
authored
Jan 26, 2015
by
HuangRui
Browse files
Merge branch 'master' of
https://github.com/nodemcu/nodemcu-firmware
into devfloat
parents
530e964d
09335d82
Changes
2
Hide whitespace changes
Inline
Side-by-side
lua_modules/dht22/README.md
View file @
04ed036c
# DHT22 module
This module is compatible with DHT22 and DHT21.
No need to use a resistor to connect the pin data of DHT22 to ESP8266.
## Example
```
lua
PIN
=
4
-- data pin, GPIO2
...
...
@@ -9,14 +12,41 @@ dht22.read(PIN)
t
=
dht22
.
getTemperature
()
h
=
dht22
.
getHumidity
()
-- temperature in degrees Celsius and Farenheit
print
(
"Temperature: "
..
(
t
/
10
)
..
"."
..
(
t
%
10
)
..
" deg C"
)
print
(
"Temperature: "
..
(
9
*
t
/
50
+
32
)
..
"."
..
(
9
*
t
/
5
%
10
)
..
" deg F"
)
if
h
==
-
1
then
print
(
"Error reading from DHT22"
)
else
-- temperature in degrees Celsius and Farenheit
print
(
"Temperature: "
..
(
t
/
10
)
..
"."
..
(
t
%
10
)
..
" deg C"
)
print
(
"Temperature: "
..
(
9
*
t
/
50
+
32
)
..
"."
..
(
9
*
t
/
5
%
10
)
..
" deg F"
)
-- humidity
print
(
"Humidity: "
..
(
h
/
10
)
..
"."
..
(
h
%
10
)
..
"%"
)
-- humidity
print
(
"Humidity: "
..
(
h
/
10
)
..
"."
..
(
h
%
10
)
..
"%"
)
end
-- release module
dht22
=
nil
package.loaded
[
"dht22"
]
=
nil
```
## Functions
### read
read(pin)
Read humidity and temperature from DHT22.
**Parameters:**
*
pin - ESP8266 pin connect to data pin in DHT22
### getHumidity
getHumidity()
Returns the humidity of the last reading.
**Returns:**
*
last humidity reading in per thousand
### getTemperature
getTemperature()
Returns the temperature of the last reading.
**Returns:**
*
last temperature reading in 0.1ºC
lua_modules/dht22/dht22.lua
View file @
04ed036c
...
...
@@ -13,23 +13,22 @@ _G[moduleName] = M
local
humidity
local
temperature
local
checksum
local
checksumTest
function
M
.
read
(
pin
)
local
checksum
local
checksumTest
humidity
=
0
temperature
=
0
checksum
=
0
-- Use Markus Gritsch trick to speed up read/write on GPIO
gpio_read
=
gpio
.
read
gpio_write
=
gpio
.
write
local
gpio_read
=
gpio
.
read
bitStream
=
{}
local
bitStream
=
{}
for
j
=
1
,
40
,
1
do
bitStream
[
j
]
=
0
end
bitlength
=
0
local
bitlength
=
0
-- Step 1: send out start signal to DHT22
gpio
.
mode
(
pin
,
gpio
.
OUTPUT
)
...
...
@@ -43,13 +42,13 @@ function M.read(pin)
-- Step 2: DHT22 send response signal
-- bus will always let up eventually, don't bother with timeout
while
(
gpio_read
(
pin
)
==
0
)
do
end
c
=
0
while
(
gpio_read
(
pin
)
==
1
and
c
<
1
00
)
do
c
=
c
+
1
end
local
c
=
0
while
(
gpio_read
(
pin
)
==
1
and
c
<
5
00
)
do
c
=
c
+
1
end
-- bus will always let up eventually, don't bother with timeout
while
(
gpio_read
(
pin
)
==
0
)
do
end
c
=
0
while
(
gpio_read
(
pin
)
==
1
and
c
<
1
00
)
do
c
=
c
+
1
end
while
(
gpio_read
(
pin
)
==
1
and
c
<
5
00
)
do
c
=
c
+
1
end
-- Step 3: DHT22 send data
for
j
=
1
,
40
,
1
do
while
(
gpio_read
(
pin
)
==
1
and
bitlength
<
10
)
do
...
...
@@ -63,17 +62,17 @@ function M.read(pin)
--DHT data acquired, process.
for
i
=
1
,
16
,
1
do
if
(
bitStream
[
i
+
0
]
>
2
)
then
if
(
bitStream
[
i
]
>
4
)
then
humidity
=
humidity
+
2
^
(
16
-
i
)
end
end
for
i
=
1
,
16
,
1
do
if
(
bitStream
[
i
+
16
]
>
2
)
then
if
(
bitStream
[
i
+
16
]
>
4
)
then
temperature
=
temperature
+
2
^
(
16
-
i
)
end
end
for
i
=
1
,
8
,
1
do
if
(
bitStream
[
i
+
32
]
>
2
)
then
if
(
bitStream
[
i
+
32
]
>
4
)
then
checksum
=
checksum
+
2
^
(
8
-
i
)
end
end
...
...
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