No connection from ST-Link

[JRS]

I have two custom boards with STM32G0B1 Chips. I am using an ST-Link V3 (V3J10M3 on Stm32CubeProgrammer - SWD default settings)to flash them.

On the first board, I could connect, but on flashing it for the first time, it reported failed to erase memory. The chip were factory-new. I checked the option bytes (no visible write protection) and tried to write them. Then the write failed and since then I could not connect with the debugger anymore.

I tried connection under reset- to no avail.

Also to pullup the Boot0 pin at POR to at least get a connection, but same result.

I checked the power pins and the reset line, it seems fine (reset pulse is visible up to the reset pin).

In short: Is there a way to connect to the chip if the option bytes are really messed up?

(without USB, SPI, USART).

[MM..1]

With connection under reset is OB not relevant, but on chips with secure modes you can block it.

Your steps seems hw issue...

[Tesla DeLorean]

What pin count or device specifically? Seem to be getting a lot of issues reported on G0 parts recently.

Is NRST connected?

For CM0(+) parts use low clock rate connections.

Not really any magic methods if SWDIO/SWCLK are rendered nonviable, or unpowered.

Walked parts out of odd states with UART before, foreclosed evidently here.

[JRS]

It is an STM32G0B1RET LQFP64 Device. NRST on Pin12 is connected and the Reset-Pulse from the Debugger is visible on the pin, though it does not seem to do anything.

HW Issues is of course possible, but as I have a second board, which can connect and be programmed, it only leaves the chip itself. Though I am still thinking the problem is in the initial failed programming of the OBs. If OB are ignored under reset, but the reset line itself could have been changed by the OB, then it would effectively lock me out.

[JRS]

As a follow up, I did try to get the part via CAN Bootloader, but also no response on PD0/PD1. POR with Boot0 high or low, did nothing, but if I interpret pattern 11 of the AN2606 correctly, in case the OB nBoot1 is 0 there is no way to get into the bootloader, so a bad OB Pattern can seemingly completely brick the device.

Thanks @Community member​ and @MM..1​ !