Same code different output between Pi3 and Pi4

Question

I got a simple rfid reader (brand unknown) connected to the serial0 rx port of a Pi4. Uploaden the following code and works perfect.

class RFID():
    def __init__(self):
        self.ser = serial.Serial(port="/dev/serial0",
                                baudrate = 9600,
                                bytesize=serial.EIGHTBITS,
                                parity=serial.PARITY_EVEN,
                                stopbits=serial.STOPBITS_ONE,
                                xonxoff=True

    def Read(self):
            while 1:
                received_data = None
                received_data = self.ser.read()
                time.sleep(0.03)
                data_left = self.ser.inWaiting()
                received_data += self.ser.read(data_left)
                self.received_data = received_data

     def returnTag(self):
            return self.received_data

The output is very neatly displayed with only giving an output after presenting the tag: b'?\xe6\xa6f\xa6\xcc\x99\x97\x97ff\xa6)\xd6\xf2\x00

Since the scanner eventually will be connected to a Pi3B I conducted the same steps strangely enough with with different result. The Pi3B is the flooding the terminal with b\x00 if nothing is detected and if the tag is presented sometimes the correct but most of the time incorrect tag values.

To check if I maybe made a setting error, I conducted the steps at the same time with both a clean installed Buster on a Pi4 and a Pi3, again with the same result.

Anybody a clue what's happening?

Answer 1

I've dun goofed myself... As the documention on the raspberryPi website states, the uart port the Rpi3 is shared with the bluetooth module.

https://www.raspberrypi.org/documentation/configuration/uart.md

After disabling the bt module in the config file everything was working perfect. Nevertheless thanks.