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Start USART Bootloader on STM32F070 device does not work

Question asked by jung.thomas.001 on May 22, 2016
Latest reply on Aug 28, 2017 by Ran Kai
Hi all,

i am using a Nucleo board "NUCLEO F070RB" and i want to start the UART Bootloader. Unfortunately the bootloader doesn´t send the Ack  byte (0x79) after activation.

My procedure to start the bootloader:
- connect the boot0 pin to 3V3
- reset the board (black botton)
- send the 0x7F Byte with 9600, even parity, 1 start bit, 1 stop bit
=> at this point i expect to receive the 0x79 ACK byte from the micro

What i did till now to find what i am doing wrong:
- i checked that nBOOT1 bit in the option bytes is set to 1
- due to the fact that the F070 device has an USB interface i removed the crystal (and i opened SB50 from the NUCLEO to avoid getting clock from the debugger)
- i am quite sure that the micro is in bootloader mode, because the application doesn´t start.
- i verified my sequence with a NUCLEO-F030RB
=> here erverything works fine. The problem just excists on the F070.
=> all my HW-connections should be ok (same Pins)

I am running out of ideas :-( 

Any help is appreciated.