dht11.lua

-- Read temperature and humidity data from DHT11 sensor.
-- Connect Data pin of DHT11 sesnor to PIN 3 (GPIO 0 - GPIO ZERO) of ESP8266 wifi module.
-- Learn: www.roboindia.com/tutorials
-- Ref-esp8266.com

pin = 3

Humidity = 0
HumidityDec=0
Temperature = 0
TemperatureDec=0
Checksum = 0
ChecksumTest=0


local function get_data()
Humidity = 0
HumidityDec=0
Temperature = 0
TemperatureDec=0
Checksum = 0
ChecksumTest=0


bitStream = {}
for j = 1, 40, 1 do
     bitStream[j]=0
end
bitlength=0

gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, gpio.LOW)
tmr.delay(20000)
--Use Markus Gritsch trick to speed up read/write on GPIO
gpio_read=gpio.read
gpio_write=gpio.write

gpio.mode(pin, gpio.INPUT)

--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

--acquisition loop
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, processing it :-

for i = 1, 8, 1 do
     if (bitStream[i+0] > 2) then
          Humidity = Humidity+2^(8-i)
     end
end
for i = 1, 8, 1 do
     if (bitStream[i+8] > 2) then
          HumidityDec = HumidityDec+2^(8-i)
     end
end
for i = 1, 8, 1 do
     if (bitStream[i+16] > 2) then
          Temperature = Temperature+2^(8-i)
     end
end
for i = 1, 8, 1 do
     if (bitStream[i+24] > 2) then
          TemperatureDec = TemperatureDec+2^(8-i)
     end
end
for i = 1, 8, 1 do
     if (bitStream[i+32] > 2) then
          Checksum = Checksum+2^(8-i)
     end
end
ChecksumTest=(Humidity+HumidityDec+Temperature+TemperatureDec) % 0xFF

print ("Temperature: "..Temperature.."."..TemperatureDec)
print ("Humidity: "..Humidity.."."..HumidityDec)
print ("ChecksumReceived: "..Checksum)
print ("ChecksumTest: "..ChecksumTest)
end


 -- Set module name as parameter of require and return module table
local M = {
  get_data = get_data
}
_G[modname or 'dht11'] = M
return M