BOOTLOADER: Can't reach the default bootloader on my own PCB (STM32F429ZI)

[TUmsc.1]

Hello all,

I worked with the Nucleo-F429ZI (which includes the STM32F429ZI) at the project start. I updated my software via UART and do following steps:

1. I connect the Nucleo-F429ZI via USB to the PC (it's the power supply too)
2. I connect a MM232R to pin PA9 and PA10 (UART1) and GND.
3. I connect the BOOT0 pin to 3V3
4. I press the reset button B2
5. I start the tool "STM32CubeProgrammer"
6. I choose UART and my MM232R, set the baudrate to 115200 and the parity to even
7. I connect the MM232R load the new software and disconnect the MM232R
8. I remove the connection of BOOT0 and 3V3
9. I press the reset button B2
10. The new software works!

Then I designed my own PCB with the STM32F429ZI. My software works on it and I can update it with the STM32CubeIDE and the SWD connection (PA13 and PA14). Now I want to update the software via UART and the bootloader:

1. I have two leds which blink during my hole software.
2. If I connect BOOT0 to 3V3 and reset the mikrocontroller the leds don't blink any more. So I think the mikrocontroller is in a special mode (maybe the bootloader?).
3. But if i want to connect via STM32CubeProgrammer following error is generated always: 13:33:39 : Error: Activating device: KO. Please, verify the boot mode configuration and check the serial port configuration. Reset your device then try again...

Additional informations:

• BOOT1 pin on my own PCB is connected with nothing. On Nucleo-F429ZI it's connected with nothing too.
• My own PCB don't use the HSE

I have very little experience with a bootloader so I hope you can help me. The functionality is very important for me and my project.

Best regards,

Tobias

[waclawek.jan]

Can't some of the bootloaders be activated before the UART bootloader? Is there activity on other bootloader pins (see AN2606)?

JW

[Tesla DeLorean]

Check AN2606, look for other pins which might be transitioning and recognized as contact. ie a GNSS receiver that starts squawking at startup.

It is not looking for the 0x7F data pattern specifically, it is using the pulse to measure a baud rate. Watch USART3

[TUmsc.1]

Thank you for the quick response!

Interfaces:

• The STM32F429 have 4 USARTS:
  • USART1: My MM232R
  • USART2 communicates with a ble module from Silicon Labs (BGM13P), baudrate=115200 (maybe this is the problem? The reset of the STM and the BGM13P are connected. After a reset the BGM13P send something)
  • USART3 is not connected
  • USART6 is not connected
• CAN2 is not connected
• I2C1 is not connected
• A USB cable is not connected too

[waclawek.jan]

It's not about the interfaces but about the pins. You can have a signal toggling from outside on e.g. PC11 and that may activate the USART3 bootloader.

Also make sure the connection you have from the USB transceiver to USART1 pins (PA10/PA9) works as expected - try e.g. echo in the application.

JW

[TUmsc.1 · Accepted solution]

Thank you for the suppert! I could solve the problem.

The connection from the USB transceiver to USART1 worked. The problem was the BOOT1 pin. After I connected it with GND I could update the software. The reason why the update works on the Nucleo-F429ZI is following: Due to the environment on the board, the pin tended towards GND. On my own PCB the pin tended towards 3V3.

[waclawek.jan]

Thanks for coming back with the solution.

JW