Program STM32H7xx over UART3 timeout

[niallp]

So new problem while trying to bypass non functioning SWD...

Using a working NUCLEO_H723 I can use the STM32CubeProgrammer to access it via STLINK (internal and external) as well as via USB DFU after reset with BOOT0 high.

From my reading of AN2606, once the bootloader has initialized, it cycles through the various options in sequence till it gets a connection (CAN first, then USARTx, I2Cx, SPIx, USB). The diagram indicates USB cable detection so I'm assuming as long as it isn't connected that the other peripherals will be checked.

I'm unclear on it checks all the possibilities for each USARTx (and I2C, SPI) or just one of them ? The only readily accessible USART is UART3 on CN10 of the Nucleo so I've started with that. Tried using RTS/DTR for BOOT0 and reset control but can't get the timing/polarity correct so just holding BOOT0 high and tried both manual reset and a pulse from DTR. I can see a single 0x7F being sent but no reply, then one more 0x7F after 2 seconds before it times out and quits.

The board works otherwise so assuming I don't have a fried serial port but maybe will have to connect to another to make sure. Open to suggestions, thanks,

[TDK]

It check all supported bootloader peripherals/pins.

Checks pins being used against supported pins in AN2606. Ensure pins being used are actually connected to the chip by looking at the user manual and/or schematic.

If SWD is not functioning, I don't expect the bootloader will function either. Sounds like the chip got killed somehow.

[niallp]

Note these tests are being done on a working NUCLEO_H723, not our (probably dead) custom board with H725. I want to make sure I can actually get STM32CubeProg to connect via serial.

Trying USART3 with Tx - PB10, Rx - PB11, connected to CN-10 pins 32, 34 respectively. MB1364 shows them connected but I guess I'd better check continuity now. Could also prove USART3 with other code.

[niallp · Accepted solution]

Turns out USART3 has conflicts with the default config on the Nucleo, as does USART1. Finally managed to get serial bootloader connection using USART2 on pins PA2, PA3 (PA2 still connected to RMII_MDIO by default but this doesn't seem to bother the bootloader).