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- -- ***************************************************************************
- -- DHTxx(11,21,22) module for ESP8266 with nodeMCU
- --
- -- Written by Javier Yanez mod by Martin
- -- but based on a script of Pigs Fly from ESP8266.com forum
- --
- -- MIT license, http://opensource.org/licenses/MIT
- -- ***************************************************************************
- --Support list:
- --DHT11 Tested ->read11
- --DHT21 Not Tested->read22
- --DHT22 Tested->read22
- --==========================Module Part======================
- local moduleName = ...
- local M = {}
- _G[moduleName] = M
- --==========================Local the UMI and TEMP===========
- local humidity
- local temperature
- --==========================Local the bitStream==============
- local bitStream = {}
- ---------------------------Read bitStream from DHTXX--------------------------
- local function read(pin)
- local bitlength = 0
- humidity = 0
- temperature = 0
- -- Use Markus Gritsch trick to speed up read/write on GPIO
- local gpio_read = gpio.read
-
-
- for j = 1, 40, 1 do
- bitStream[j] = 0
- end
-
- -- Step 1: send out start signal to DHT22
- gpio.mode(pin, gpio.OUTPUT)
- gpio.write(pin, gpio.HIGH)
- tmr.delay(100)
- gpio.write(pin, gpio.LOW)
- tmr.delay(20000)
- gpio.write(pin, gpio.HIGH)
- gpio.mode(pin, gpio.INPUT)
- -- Step 2: Receive bitStream from DHT11/22
- -- bus will always let up eventually, don't bother with timeout
- while (gpio_read(pin) == 0 ) do end
- local c=0
- while (gpio_read(pin) == 1 and c < 500) 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 < 500) 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
- bitlength = bitlength + 1
- end
- bitStream[j] = bitlength
- bitlength = 0
- -- bus will always let up eventually, don't bother with timeout
- while (gpio_read(pin) == 0) do end
- end
- end
- ---------------------------Convert the bitStream into Number through DHT11 Ways--------------------------
- function M.read11(pin)
- --As for DHT11 40Bit is consisit of 5Bytes
- --First byte->Humidity Data's Int part
- --Sencond byte->Humidity Data's Float Part(Which should be empty)
- --Third byte->Temp Data;s Intpart
- --Forth byte->Temp Data's Float Part(Which should be empty)
- --Fifth byte->SUM Byte, Humi+Temp
- read(pin)
- local checksum = 0
- local checksumTest
- --DHT data acquired, process.
- for i = 1, 8, 1 do -- Byte[0]
- if (bitStream[i] > 3) then
- humidity = humidity + 2 ^ (8 - i)
- end
- end
- for i = 1, 8, 1 do -- Byte[2]
- if (bitStream[i + 16] > 3) then
- temperature = temperature + 2 ^ (8 - i)
- end
- end
- for i = 1, 8, 1 do --Byte[4]
- if (bitStream[i + 32] > 3) then
- checksum = checksum + 2 ^ (8 - i)
- end
- end
- if(checksum ~= humidity+temperature) then
- humidity = nil
- temperature = nil
- end
-
- end
- ---------------------------Convert the bitStream into Number through DHT22 Ways--------------------------
- function M.read22( pin )
- --As for DHT22 40Bit is consisit of 5Bytes
- --First byte->Humidity Data's High Bit
- --Sencond byte->Humidity Data's Low Bit(And if over 0x8000, use complement)
- --Third byte->Temp Data's High Bit
- --Forth byte->Temp Data's Low Bit
- --Fifth byte->SUM Byte
- read(pin)
- local checksum = 0
- local checksumTest
- --DHT data acquired, process.
- for i = 1, 16, 1 do
- if (bitStream[i] > 3) then
- humidity = humidity + 2 ^ (16 - i)
- end
- end
- for i = 1, 16, 1 do
- if (bitStream[i + 16] > 3) then
- temperature = temperature + 2 ^ (16 - i)
- end
- end
- for i = 1, 8, 1 do
- if (bitStream[i + 32] > 3) then
- checksum = checksum + 2 ^ (8 - i)
- end
- end
- checksumTest = (bit.band(humidity, 0xFF) + bit.rshift(humidity, 8) + bit.band(temperature, 0xFF) + bit.rshift(temperature, 8))
- checksumTest = bit.band(checksumTest, 0xFF)
- if temperature > 0x8000 then
- -- convert to negative format
- temperature = -(temperature - 0x8000)
- end
- -- conditions compatible con float point and integer
- if (checksumTest - checksum >= 1) or (checksum - checksumTest >= 1) then
- humidity = nil
- end
- end
- ---------------------------Check out the data--------------------------
- function M.getTemperature()
- return temperature
- end
- function M.getHumidity()
- return humidity
- end
- return M
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