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I've recently build my own dev board utilizing the ESP32-C3-MINI-1-N4 module. Everything works pretty well and just as expected, I can control a few onboard LEDs just fine and upload code and everything. The only (major) problem is that I apparently can't receive any Serial data. When using the Arduino VSCode Extensions Serial Monitor I get an error:

VSCode error message

the error is highlighted and German, it translates to something like

Error opening the serial port /dev/ttyACM0

In the top, you can also see my very simple test code. On pin 2 there's an LED which blinks just as expected.

When using screen /dev/ttyACM0 115200, I just get an empty screen, no error message but also no output. The same goes for tio:

TIO (no error message

When using the Arduino IDE on Windows, I don't get any error messages but only a blank Serial Monitor as well. I'm really out of ideas and would really appreciate any help you could give me.

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  • \$\begingroup\$ Are you using the USB pins on the C3 for serial debugging or a USB to UART bridge connected to the UART pins? \$\endgroup\$
    – Microcontroller Enjoyer
    Commented Jun 10 at 14:23
  • \$\begingroup\$ I'm using the internal USB to UART interface of the ESP, not an external one. \$\endgroup\$
    – EmilEmilchen
    Commented Jun 10 at 14:39
  • \$\begingroup\$ Not sure how it works with the Arduino VSCode extensions, but on PlatformIO there's some build flags that are required to enable USB CDC which I believe is required to use the Serial() functions over the USB pins. \$\endgroup\$
    – Microcontroller Enjoyer
    Commented Jun 10 at 14:41
  • \$\begingroup\$ Okay, I just tried it and it turns out that I just have to enable "USB CDC On Boot", and then serial works, the problem I'm encountering now is that I'm now unable to flash any new code without entering "Joint Download Mode" by pulling GPIO8 HIGH and GPIO9 LOW. This is especially problematic as I didn't incorporate any access to GPIO8 as, at the time, I thought GPIO9 was the only GPIO necessary for boot mode selection. I now have to desolder the entire chip and solder wires to it manually every time. Could there be any software based solution? \$\endgroup\$
    – EmilEmilchen
    Commented Jun 10 at 15:46
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    \$\begingroup\$ Thank you for your advice! I now just ordered new PCBs. \$\endgroup\$
    – EmilEmilchen
    Commented Jun 13 at 13:06

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