Arduino for STM32

Yes. MCU with USB non OTG requires a PU while USB OTG has internal PU anyway several board with it has an external PU.

The fact is that this toggling was done in Roger's core, and is no more done in the STM32Duino core. So I must add the few lines above before initializing the Serial port.

This is done in the core Phono. As I said before. ..

But I just think that you talk about a discovery pin. So in your variant you have to define it.

You are right, my board has the discovery pin. And this one is not automatically handled by the core.

hi Phono,
if you make a variant, you may like to contribute that to the core. i think many people has this board
i.e. the stm32f103rb from Olimex
https://www.olimex.com/Products/Duino/S ... e-hardware
it is a nice board, one of those features they replicated is they use a separate LDO for the ADC supply, that reduce noise
it has a micro-sd card slot on SPI2
and an on board lipo charger and power supply

You are right, this is a good board especially for the applications where the CAN bus is needed.

the only slight dislike is the use of micro pins for swd/jtag, which requires a connecting adapter and it makes some pins that has double functions less accessible there. but the rb has quite a lot of pins, so it is normally adequate at other ports

Phono if you use the generic variant then define the USB disc pin:
#define USB_DISC_PIN PYn


You can use the hal_conf_extra.h or the build_opt.h to do this

Just for reference, the USB_DISC pin toggling is implemented here:
https://github.com/stm32duino/Arduino_C ... #L131-L152