ST-Link/V3 MINIE / V3 Mods UART flash

[yaawl]

I have a question for you. The STM32 F303 processor can be programmed using the UART interface. I have ST-Link/V3 MINIE and V3-Mods and I'm trying to flash the processor using UART (I know it's possible via SWD but I absolutely need UART) After connecting to my board with STM32, I'm trying to connect the processor via the cube programmer but without success.

It says Error: Activating device: KO. Please, verify the boot mode configuration and check the serial port configuration. Reset your device then try again. I have the board powered by 3V especially because the MINIE does not contain power pins. Am I missing an error? Can you think of what I'm doing wrong?

My question is is it even possible to use MINIE or V3mods to program the processor using UART? thanks for any answer

[TDK]

You need to start the chip in bootloader mode in order for the UART programming interface to be active. To do this, generally you need BOOT0 to be 3.3V during reset.

[yaawl]

Thanks for your answer. We have BOOT0 connected to 3.3V during testing. Both BOOT0 and reset are connected to 3.3V. Parities we have sec. Baud rate 115200. Does the BOOT0 always have to be at 1 or only when connecting? thank you for answer. When we tried it via FTDI, I normally connect and flash the board. But for our purpose, I need a device (ST-Link V3) that can handle both SWD and UART

[TDK]

It only needs to be 3.3V immediately after reset.

Perhaps show how the devices are connected and verify pins are correct. Verify on a scope or logic analyzer than stm32cubeprogrammer is outputting signals on the appropriate line. It should be possible.

[yaawl]

What do you mean after reset? When connecting to the board or when connecting to target in cube programmer? Because i dont have reset button on the board.

[TDK]

"immediately after reset" means "when NRST goes from low to high".

If you don't have control of NRST, tie BOOT0 to 3.3V on powerup as NRST goes from low to high on powerup.

[yaawl]

I have pins on my board GND / TX / RX / BOOT0 / RST / 3V3. Can you please tell me how i connect this to ST-Link V3 MODS ? My board have RST in HIGH. I dont know what we can use on V3 MODS VCP, CAN or BRIDGE UART ? I plug V3 MODS to the pc, i choose in cube programmer COM and parity even (tested odd, none). When i click on connect  show me Error: Activating device: KO. Please, verify the boot mode configuration and check the serial port configuration. See attached image. We dont know where we connect RST and BOOT. And GND detect must be connected to ground ? Please help, thank you so much !