what are boot loader reserved pins for first programming?

[PR.10]

Hi, I have a board with STM32G071KBU6N with new and empty flas.

I have difficulty programming it because it seems to set some pins as output after power up. for example PA6 and PB7. This is causing a over current in the circuit.

I suspect some kind of built in boot loader is running and doing this.

There is 100nF to gnd on reset pin without any pull resistor. I also tried add pull up and pull down on pb14/boot0 without any effect.

how to prevent the boot loader from running and keep all pins as inputs until the device is programmed?

Is it even possible or do I have to reserve some pins to be outputs because of this?

[TDK]

There is a "connect under reset" option in STM32CubeProgrammer. You can try that.

[Kraal]

Good find Jan !

[PR.10]

I have tried all of hem at the beginning :-), but none of them holds reset. At least not with my nucleo board. I think they only work after pressing connect button, by which time the cpu is already running. The tutorial suggests that reset has to by held by an external connection and it does seem to be the case. It is not mass production solution, but with some additional wireds/soldering the board can be recovered this way.

[waclawek.jan]

I made a faint attempt to ask ST to implement a direct control of reset. Note the date of that thread. Given how CubeProgrammer is a showcase of all "fresh new exciting ideas" like throwing controls all over the place, and focus on "modern feel and look", I doubt anybody gave this a though.

But you can ask them to implement that properly, too.

JW