2026-05-13 11:13 PM - last edited on 2026-05-14 1:47 AM by mƎALLEm
I was wondering what is that. I created a custom bootloader firmware and application firmware. But once I successfully uploaded. When I send application firmware resquest I do not receive application firmware responses. Why is that? what is that? do you recognize that?
The AA 01 00 00 BB is the application firmware request frame.
0xAA is the begining
0x01 is the length
0x00 is the frame request ID
0x00 is the checksum
0xBB is the end of the frame
Thanks for all.
2026-05-13 11:42 PM
Is this UART?
Too many 1s (FFs and similar) usually indicate baudrate mismatch. Factory bootloader autobauds, do that's unlikely to be the culprit.
Using debugger may help immensely.
JW
2026-05-14 12:44 AM
What kind of baudrate mismatch. All is at 9600 baud rate.
2026-05-14 1:26 AM
Well, you don't know what is it what's responding to you. That is running at a different baudrate.
Observe the reply using oscilloscope or logic analyzer and infer the baudrate from the shortest pulse length. Or listen to it using a terminal program in PC which allows you to change baudrate and display framing errors.
It may well be your program, too, with misconfigured clocks or UART.
JW
2026-05-14 1:51 AM
Hello,
The question is not clear.
You are using a custom bootloader on LPUART and you are asking about ST bootloader in the title? knowing that ST bootloader doesn't use LPUART for that device: