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dht22v2.lua
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dht22v2.lua
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-- ***************************************************************************
-- DHT11 module for ESP8266 with nodeMCU
--
-- Written by Javier Yanez
-- but based on a script of Pigs Fly from ESP8266.com forum
--
-- MIT license, http://opensource.org/licenses/MIT
-- ***************************************************************************
local moduleName = ...
local M = {}
_G[moduleName] = M
local humidity
local temperature
local checksum
local checksumTest
local checko1
local checko2
function M.read(pin)
humidity = 0
temperature = 0
checksum = 0
checko1=0
checko2=0
-- Use Markus Gritsch trick to speed up read/write on GPIO
gpio_read = gpio.read
gpio_write = gpio.write
bitStream = {}
for j = 1, 40, 1 do
bitStream[j] = 0
end
bitlength = 0
-- Step 1: send out start signal to DHT11
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: DHT11 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 < 100) 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 < 100) do c = c + 1 end
-- Step 3: DHT11 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
--DHT data acquired, process.
for i = 1, 8, 1 do
if(bitStream[i+0]>2)then
humidity=humidity+2^(8-i)
end
if(bitStream[i+8]>2)then
checko1=checko1+2^(8-i)
end
if(bitStream[i+16]>2)then
temperature=temperature+2^(8-i)
end
if(bitStream[i+24]>2)then
checko2=checko2+2^(8-i)
end
if (bitStream[i+32]>2)then
checksum=checksum+2^(8-i)
end
end
checksumTest=(humidity+checko1+temperature+checko2)%256
-- convert to negative format
--if temperature > 0x8000 then temperature = -(temperature - 0x8000)
--end
if checksum ~= checksumTest then
humidity = -1
end
end
function M.getTemperature()
return temperature
end
function M.getHumidity()
return humidity
end
return M