nodemcu-firmware/lua_modules/dht22/dht_lib.lua

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-- ***************************************************************************
-- DHTxx(11,21,22) module for ESP8266 with nodeMCU
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--
-- Written by Javier Yanez mod by Martin
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-- 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======================
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local moduleName = ...
local M = {}
_G[moduleName] = M
--==========================Local the UMI and TEMP===========
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local humidity
local temperature
--==========================Local the bitStream==============
local bitStream = {}
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---------------------------Read bitStream from DHTXX--------------------------
local function read(pin)
local bitlength = 0
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humidity = 0
temperature = 0
-- Use Markus Gritsch trick to speed up read/write on GPIO
local gpio_read = gpio.read
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for j = 1, 40, 1 do
bitStream[j] = 0
end
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-- 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
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-- 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
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-- 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
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-- 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
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--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.
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for i = 1, 16, 1 do
if (bitStream[i] > 3) then
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humidity = humidity + 2 ^ (16 - i)
end
end
for i = 1, 16, 1 do
if (bitStream[i + 16] > 3) then
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temperature = temperature + 2 ^ (16 - i)
end
end
for i = 1, 8, 1 do
if (bitStream[i + 32] > 3) then
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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)
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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
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end
end
---------------------------Check out the data--------------------------
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function M.getTemperature()
return temperature
end
function M.getHumidity()
return humidity
end
return M