hlpm025k3.py

from umachine import UART
import utime as time

debug = False

class Driver:
  def __init__(self, uart):
    if type(uart) is not UART:
      raise ValueError("%s is not a valid type" % uart)
    self.uart = uart
    
  def readMsg(self):
    # At least wait for 1 sec for incomming message
    time.sleep_ms(1200)
    buffer = bytearray(7)
    counter = 0
    while True:
      char = self.uart.read(1)
      if char == b'\xaa':
        counter = 0
      buffer[counter] = int.from_bytes(char, 'little')
      counter += 1
      if char == b'\xff':
        break
    if debug:
      print("recvived buffer :" + buffer)
    if buffer[0] != 0xAA and buffer[6] != 0xFF:
      raise OSError("Invalid MSG format")
    return buffer
  
  def parseMsg(self, msg):
    pm25 = (msg[1] * 256 + msg[2]) * 0.1
    pm10 = (msg[3] * 256 + msg[4]) * 0.1
    # should check the CRC
    crc = msg[5]
    if debug:
      print("parse message: pm25 = %d, pm10=%d, crc = 0x%x" % (pm25, pm10, crc))
    return (pm25, pm10, crc)
  
  def getData(self):
    msg = self.readMsg()
    pm25, pm10, crc = self.parseMsg(msg)
    return (pm25, pm10)