Broken device through optoin bytes

[machinist]

Hello,

I am currently fiddling around with a STM32G491 in bare metal. I wanted to test the write protection. So I executed following code

	FLASH->KEYR = FLASH_KEY1;
	FLASH->KEYR = FLASH_KEY2;
	while(FLASH->CR&bit31);		// wait for unlock
	FLASH->OPTKEYR = FLASH_OPTKEY1;
	FLASH->OPTKEYR = FLASH_OPTKEY2;
	while(FLASH->CR&bit30);		// wait for option unlock
	//#define PROTECT(start, end)	FLASH->WRP1AR = (((start>>11)&0xFF)|(((end>>11)&0xFF)<<16))
	PROTECT(0x5000, 0x6000);
	FLASH->CR |= bit17;			// option start 
	while(FLASH->CR&bit17);		// wait for option done
	FLASH->CR |= bit27;			// option load 
	while(FLASH->CR&bit27);		// wait for option reload done
	FLASH->CR |= bit30;			// lock option
	FLASH->CR |= bit31;			// lock 

Just to note my code worked fine (except the locking) until I added line 12. It seems the OB_LAUNCH bit is never reset to 0.

The problem is now that I can not reach my device any more. I am connected through SWD via STlinkV2 with a hardware reset connectd. But none of the connection methods works any more using STProg or STCubeIDE. Not even connect under reset works. How can that be? Is there anything I can do to erase it?

Edit: the error I get is

Target no device found

Error in initializing ST-LINK device.

Reason: No device found on target.

[Tesla DeLorean · Accepted solution]

Is it stuck running this code again? 

Try pulling BOOT0 High?

[machinist]

Thanks for the reply. But it didnt do anything pulling boot0 to high. Also not when trying to connect while Boot0 is high.

I hooked up a logic analyzer to the reset line. I see ~3,8ms high pulse every ~140ms. The reset is low otherwise. Also when the STLink is not connected these pulses are there.

This pattern does not change if the STlink is connected and I try to connect under reset. Shouldn't the STlink pull the reset low in order to connect?

[machinist]

Working again. Seems fiddeling with the Boot0 pin high and low while connecting somehow anabled STprog to connect.

Thanks.