How to use RFID module MFRC522-UART serial on python 3? (encoding/decoding issue)

I am trying to use a modified MFRC522 module on UART, but I am stuck finding the correct formatting for serial read/write in python 3.

There is a library for python 2 which works for me:

The readme on that link also describes the modification to the module.

I'm having trouble getting the .self.ser.write and .self.ser.read in functions writeRegister and readRegister to work in python 3. These get string inputs, which I now understand is fine for python 2, but must be converted to bytes for python 3.

def writeRegister(self, addr, val, size=None):
    if size is None:
      count = 0
      while True:
        self.ser.flushInput()
        self.ser.write(chr(addr&0x7F))
        self.ser.write(chr(val))
        tmp = ord(self.ser.read(1))   
        if(tmp == addr):      
          return True
        count+=1
        if(count > 10):
          print ("Error de escritura en: "+ hex(addr))
          return False  
    else:       
      self.ser.flushInput()
      for txBytes in range (0, size):
        self.ser.write(chr(addr&0x7F))
        tmp = ord(self.ser.read(1))
        if(tmp == addr):
          self.ser.write(chr(val[txBytes]))
        else:
          print ("Error de escritura en bloque")
          return False

      return True    

  def readRegister(self, addr):
    self.ser.flushInput()
    self.ser.write(chr(addr|0x80))
    val = self.ser.read(1)
    return ord(val)

I suspected it's a matter of correctly applying .encode('utf-8') or similar, but I can't find a working solution. If I try

chr(0x80).encode('utf-8')

I get

UnicodeDecodeError: 'ascii' codec can't decode byte 0x80 in position 0: ordinal not in range(128)

Maybe I am going down the wrong path with that.
I'll try bytes:

bytes(chr(0x80), 'utf-8')

Gives 2 bytes in this case (>128 i guess):

b'\xc2\x80'

Maybe this is getting closer, but I get stuck on how to read back and decode. I don't know how or if to modify the ord parts. So I can't seem to get the response from the mfrc522.

Does anyone have any suggestions?
Anybody successfully used this mfrc522 UART on python 3?

Solution

There should be no need to use char in either Python 2.x or 3.x, you can just write bytes to the port: self.ser.write(bytes[addr&0x7F])

For the reading function just drop the ord() from the return sentence, it's not needed for Python 3.x.

See here for more details.