Merge branch 'master' of https://github.com/nodemcu/nodemcu-firmware into devfloat
This commit is contained in:
commit
04ed036cc1
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@ -1,5 +1,8 @@
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# DHT22 module
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# DHT22 module
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This module is compatible with DHT22 and DHT21.
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No need to use a resistor to connect the pin data of DHT22 to ESP8266.
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## Example
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## Example
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```lua
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```lua
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PIN = 4 -- data pin, GPIO2
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PIN = 4 -- data pin, GPIO2
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@ -9,14 +12,41 @@ dht22.read(PIN)
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t = dht22.getTemperature()
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t = dht22.getTemperature()
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h = dht22.getHumidity()
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h = dht22.getHumidity()
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if h == -1 then
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print("Error reading from DHT22")
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else
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-- temperature in degrees Celsius and Farenheit
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-- temperature in degrees Celsius and Farenheit
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print("Temperature: "..(t / 10).."."..(t % 10).." deg C")
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print("Temperature: "..(t / 10).."."..(t % 10).." deg C")
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print("Temperature: "..(9 * t / 50 + 32).."."..(9 * t / 5 % 10).." deg F")
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print("Temperature: "..(9 * t / 50 + 32).."."..(9 * t / 5 % 10).." deg F")
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-- humidity
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-- humidity
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print("Humidity: "..(h/10).."."..(h%10).."%")
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print("Humidity: "..(h/10).."."..(h%10).."%")
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end
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-- release module
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-- release module
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dht22 = nil
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dht22 = nil
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package.loaded["dht22"]=nil
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package.loaded["dht22"]=nil
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```
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```
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## Functions
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### read
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read(pin)
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Read humidity and temperature from DHT22.
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**Parameters:**
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* pin - ESP8266 pin connect to data pin in DHT22
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### getHumidity
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getHumidity()
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Returns the humidity of the last reading.
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**Returns:**
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* last humidity reading in per thousand
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### getTemperature
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getTemperature()
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Returns the temperature of the last reading.
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**Returns:**
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* last temperature reading in 0.1ºC
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@ -13,23 +13,22 @@ _G[moduleName] = M
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local humidity
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local humidity
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local temperature
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local temperature
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local checksum
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local checksumTest
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function M.read(pin)
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function M.read(pin)
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local checksum
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local checksumTest
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humidity = 0
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humidity = 0
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temperature = 0
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temperature = 0
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checksum = 0
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checksum = 0
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-- Use Markus Gritsch trick to speed up read/write on GPIO
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-- Use Markus Gritsch trick to speed up read/write on GPIO
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gpio_read = gpio.read
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local gpio_read = gpio.read
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gpio_write = gpio.write
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bitStream = {}
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local bitStream = {}
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for j = 1, 40, 1 do
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for j = 1, 40, 1 do
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bitStream[j] = 0
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bitStream[j] = 0
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end
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end
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bitlength = 0
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local bitlength = 0
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-- Step 1: send out start signal to DHT22
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-- Step 1: send out start signal to DHT22
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gpio.mode(pin, gpio.OUTPUT)
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gpio.mode(pin, gpio.OUTPUT)
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@ -43,12 +42,12 @@ function M.read(pin)
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-- Step 2: DHT22 send response signal
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-- Step 2: DHT22 send response signal
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-- bus will always let up eventually, don't bother with timeout
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-- bus will always let up eventually, don't bother with timeout
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while (gpio_read(pin) == 0 ) do end
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while (gpio_read(pin) == 0 ) do end
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c=0
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local c=0
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while (gpio_read(pin) == 1 and c < 100) do c = c + 1 end
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while (gpio_read(pin) == 1 and c < 500) do c = c + 1 end
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-- bus will always let up eventually, don't bother with timeout
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-- bus will always let up eventually, don't bother with timeout
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while (gpio_read(pin) == 0 ) do end
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while (gpio_read(pin) == 0 ) do end
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c=0
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c=0
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while (gpio_read(pin) == 1 and c < 100) do c = c + 1 end
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while (gpio_read(pin) == 1 and c < 500) do c = c + 1 end
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-- Step 3: DHT22 send data
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-- Step 3: DHT22 send data
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for j = 1, 40, 1 do
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for j = 1, 40, 1 do
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@ -63,17 +62,17 @@ function M.read(pin)
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--DHT data acquired, process.
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--DHT data acquired, process.
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for i = 1, 16, 1 do
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for i = 1, 16, 1 do
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if (bitStream[i + 0] > 2) then
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if (bitStream[i] > 4) then
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humidity = humidity + 2 ^ (16 - i)
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humidity = humidity + 2 ^ (16 - i)
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end
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end
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end
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end
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for i = 1, 16, 1 do
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for i = 1, 16, 1 do
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if (bitStream[i + 16] > 2) then
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if (bitStream[i + 16] > 4) then
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temperature = temperature + 2 ^ (16 - i)
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temperature = temperature + 2 ^ (16 - i)
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end
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end
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end
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end
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for i = 1, 8, 1 do
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for i = 1, 8, 1 do
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if (bitStream[i + 32] > 2) then
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if (bitStream[i + 32] > 4) then
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checksum = checksum + 2 ^ (8 - i)
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checksum = checksum + 2 ^ (8 - i)
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end
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end
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end
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end
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