SDS011 + ESP8266

init.lua

DEVICE_ID="pmsensor-" .. string.format("%02X", node.chipid())

BOOT_WAIT = 3
DWEET_INTERVAL = 60
LED_PIN = 4

pm25 = nil
pm10 = nil

function led(state)
   gpio.mode(LED_PIN, gpio.OUTPUT)
   if state == 0 then
      gpio.write(LED_PIN, gpio.HIGH)
   elseif state == 1 then
      gpio.write(LED_PIN, gpio.LOW)
   else
      if gpio.read(LED_PIN) == gpio.HIGH then
         led(1)
      else
         led(0)
      end
   end
end

function dweet()
   led(0)
   url = "https://dweet.io/dweet/for/" .. DEVICE_ID
   headers = 'Content-Type: application/json\r\n'
   payload = '{"pm25":' .. pm25 .. ',"pm10":' .. pm10 .. '}'
   print("Dweeting measurements: " .. payload)
   http.post(
      url, headers, payload,
      function (code, data)
         if not code == 200 then
            print("Dweet failed, code: " .. code .. ", response: " .. data)
         else
            print("Measurements dweeted successfully: " .. data)
            led(1)
         end
      end
   )
end

function boot()
   uart.setup(0, 9600, 8, uart.PARITY_NONE, uart.STOPBITS_1, 1)
   uart.on(
      "data", "\171",
      function (data)
         if string.len(data) == 10 then
            header, command, pm25l, pm25h, pm10l, pm10h, id1, id2, sum, tail = struct.unpack("BBBBBBBBBB", data)
            if header == 0xAA and command == 0xC0 and (pm25l + pm25h + pm10l + pm10h + id1 + id2) % 256 == sum and tail == 0xAB then
               pm25 = (pm25h * 256 + pm25l) / 10
               pm10 = (pm10h * 256 + pm10l) / 10
               print("Received SDS011 message, PM 2.5: " .. pm25 .. ", PM 10: " .. pm10)
            else
               print("Malformed SDS011 message")
            end
         else
            print("Invalid SDS011 message size")
         end
      end,
      0
   )

   tmr.alarm(
      0, DWEET_INTERVAL * 1000, tmr.ALARM_AUTO,
      function ()
         if pm25 and pm10 then
            dweet()
         end
      end
   )
end

function setup()
   tmr.alarm(
      0, 100, tmr.ALARM_AUTO,
      function ()
         led()
      end
   )

   enduser_setup.start(
      function()
         tmr.unregister(0)
         led(1)
         boot()
      end,
      function(err, str)
         print("enduser_setup: Error #" .. err .. ": " .. str)
      end
   );
end

tmr.alarm(0, BOOT_WAIT * 1000, tmr.ALARM_SINGLE, setup)