I want to know if it is possible to use the arduino uno's built-in FTDI chip as a USB to ttl adapter (instead of an FT232). I have shorted the uno's Reset pin to GND, and have connected the RX and TX pins to the A9 and A10 pins of the STM32, respectively. I can upload code from the arduino IDE, but nothing happens on the board.

I am wondering if it is because I am trying to program with an Uno rather than a designated USB to TTL device.

  • \$\begingroup\$ what is the state of the BOOT pins on the Blue Pill? you have to change them for upload versus run \$\endgroup\$
    – Juraj
    Jun 3, 2023 at 5:39

1 Answer 1


The Arduino IDE assumes there's an arduino bootloader on your device that accepts data via serial.

If that's not the case, the Arduino IDE doesn't know what to do.

You would need to get one of these cheap stlink v2 / v3 clones and program the Arduino bootloader.

  • \$\begingroup\$ the STM32 has a bootloader from factory and OP is able to use it \$\endgroup\$
    – Juraj
    Jun 3, 2023 at 5:37
  • \$\begingroup\$ @Juraj I thought the Arduino platform requires a specific bootloader? \$\endgroup\$ Jun 3, 2023 at 8:28
  • \$\begingroup\$ there is no Arduino specific bootloader. there are a few bootloaders modified by Arduino, but there is nothing Arduino specific on their usage. a bootloader is only about how to get the binary into the flash memory. \$\endgroup\$
    – Juraj
    Jun 3, 2023 at 8:55

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