STM32L412 UART bootloader not writing data

[fabces]

Hi,

I'm curentlly in the process of switching to a STM32L412 from an STM32F3 on a custom design and I'm having an issue with the UART bootloader. The bootloader worked as intended on the F3 chip but on the L4 chip I can't write to the chip.

Everything works until then, I can enter the bootloader mode and erase the flash but when it comes to writing I never get a ACK or NACK back and it just spins.

I tried various commands like "Get Version & Read Protection Status command" interestingly I only get 00s and then a ACK, which is strange, I should at least get the version number.

The UART baud rate is 1152000 (I also tried slower speeds to no avail). The commands are sent from another ARM.

Any help would be greatly appreciated, thanks!

Fabien

[TDK]

> I never get a ACK or NACK back and it just spins

> interestingly I only get 00s and then a ACK, which is strange

Getting 0s and ACKs means it's doing something. Double check your settings. Even parity. Put a scope on the lines to see what is happening. It is unlikely that there is a bug in the bootloader, so look for bugs in your code.

> The UART baud rate is 1152000

Presumably you meant 115200.