Trouble with PySerial read

Question

I'm trying to read data from an Arduino serial monitor, but I'm having problems with pyserial's readline function. Here's the simple code which prints to the monitor:

void setup() {
  Serial.begin(19200);
}

void loop() {
  Serial.print("helloWorld");
  delay(1);        // delay in between reads for stability
}

And here's the Python code I'm using to read the printed output:

import serial
arduinoSerialData = serial.Serial()
arduinoSerialData.port = "COM4"
arduinoSerialData.baudrate = 19200
arduinoSerialData.timeout = 1
arduinoSerialData.setDTR(False)
#arduinoSerialData.setRTS(False)
arduinoSerialData.open()
while(True):
    b = arduinoSerialData.readline().decode('utf-8').strip().split(',')
    print(b)

This is the error:

  File "SerialRead.py", line 11, in <module>
    str_b = b.decode()
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x91 in position 7: invalid start byte

I have no clue what could be going wrong. Does anyone have any suggestions? Thank you for your time!

What exactly is the Arduino sending out the serial port? Nothing is shown in the code you posted. — jasonharper, Sep 18 '20 at 00:42
@jasonharper Sorry, I left out a line by mistake. It should be fixed now, but the error is still coming up. — Jonathan Lee, Sep 18 '20 at 20:39

score 1 · Answer 1 · answered Sep 23 '20 at 08:51

I have this code, and this is perfect:

import serial

Ser=serial.Serial(port='com8',baudrate='9600',timeout=1)

while True:
    print(Ser.readline())

Convert this data to string, and remove uneccesary character. Example:

import serial

Ser=serial.Serial(port='com8',baudrate='9600',timeout=1)

while True:
    data=Ser.readline()
    data=str(data)
    try:
        dat1=data.replace("b","")
        dat2=dat1.replace("\r\n","")
        dat3=dat2[:-5]
        dat4=dat3.replace("'", "")
        print(dat4)
    except:
        print("ERROR: replace method error")

Good luck!

Trouble with PySerial read

1 Answers1