ESP32-C3 framework arduino Serial.print USB

maxgerhardt · November 14, 2022, 2:23pm

Whether the Arduino-ESP32 framework uses hardware UART or USB-CDC as Serial depends on the value of the macros

espressif/arduino-esp32/blob/8ee5f0a11e5423a018e0f89146e05074466274db/cores/esp32/HWCDC.h#L101-L107


      
          #if ARDUINO_USB_MODE
          #if ARDUINO_USB_CDC_ON_BOOT//Serial used for USB CDC
          extern HWCDC Serial;
          #else
          extern HWCDC USBSerial;
          #endif
          #endif

github.com

espressif/arduino-esp32/blob/8ee5f0a11e5423a018e0f89146e05074466274db/cores/esp32/USBCDC.cpp#L449-L451


      
          #if ARDUINO_USB_CDC_ON_BOOT && !ARDUINO_USB_MODE //Serial used for USB CDC
          USBCDC Serial(0);
          #endif

So ARDUINO_USB_MODE can either be 0 or 1 (for either hardware USB-CDC or TinyUSB) but ARDUINO_USB_CDC_ON_BOOT must be 1.

Some board = ... selections preselect the value for you,

github.com

platformio/platform-espressif32/blob/develop/boards/lolin_c3_mini.json#L7-L11


      
          "extra_flags": [
            "-DARDUINO_LOLIN_C3_MINI",
            "-DARDUINO_USB_MODE=1",
            "-DARDUINO_USB_CDC_ON_BOOT=1"
          ],

while others do not.

So as a first try, add

board_flags =
   -DARDUINO_USB_CDC_ON_BOOT=1

in the platformio.ini and reupload the firmware.