I am trying to read potential meter data from Arduino using python, with the program on Arduino as follows :

#include <cvzone.h>

SerialData serialData;
int sendVals[2];

void setup() {

void loop() {
  int potVal = analogRead(A0);
  sendVals[0]= potVal;

the program on the arduino side is running fine

and program in python as follows

from cvzone.SerialModule import SerialObject

arduino = SerialObject("COM7")

while True:
   data = arduino.getData()

but i get error :(

Traceback (most recent call last): data = arduino.getData() File "C:...\site-packages\cvzone\SerialModule.py", line 68, in getData data = data.decode("utf-8") UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf7 in position 0: invalid start byte

how to solve it?

  • the new USB connection resets the Mega and it spends some time in bootloader waiting for upload.
    – Juraj
    Dec 6 '21 at 13:32
  • Maybe add some delay on the Arduino after initializing the serialData in startup() before it starts sending data in the loop().
    – Dave X
    Dec 6 '21 at 14:45

I would embed the call to .getData() into a try block and handle this specific exception with except UnicodeDecodeError. There can always be a transmission error, especially when the script is started.

However, I would do it differently:

void loop() {

...and on the python side use serial.readline() from pyserial instead. But I don't know cvzone and you might have a reason to use this instead of the commonly used pyserial.


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