ESP32C3 - Any PWM output creates serial port interference.

[andrewpriddis]

I have a simple piece of code that reads a pin and writes the state to a serial port (USB) every 500 milliseconds. If the pin is HIGH then a pwm signal is wrttien to the tonePin with a duty cycle of 128. Either 00 or FF should be written out the port. This works great unless I add the analogWirte function to the code. If I do then that serial data becomes garbage. See code below and then serial output examples below that.

    if ((millis() - writePauseTimer) > 500)
    {
        if (digitalRead(inputPin))
        {
            pauseState = 0xff;
            analogWrite(tonePin, 128);
        }
        else
        {
            pauseState = 0;
        }
        Serial.write(pauseState);
        writePauseTimer = millis();
    }

This is the garbage written out the serial port when the button is pushed. It appears that the PWM timer is messing with the serial port.

[MatthewJeffson]

Thanks for the information here! I really appreciated!

[andrewpriddis]

@MatthewJeffson - Any ideas on how I can handle this?

[andrewpriddis]

@MatthewJeffson - Any help on this?

[grilliiiii]

Hi andrewpriddis
I've tried adding the serial print code to our PWM demo, and the serial monitor is outputting the print information correctly. Perhaps you could double-check the rest of your code to see if something is causing the confusion?

[andrewpriddis]

Ok, I put the serial monitor into text mode and now I see what all the garbage is.... all the extra text coming over the port. How do I shut that off? I was viewing as Hex expecting to only see 1s and 0s like your example...