6 out of 11 boards eventually reset right after starting.

Forum|Forum|3 years ago
November 7, 2022
13 replies
3717 views

I have 11 boards of our prototype with the STM32L4A6AGI6 (i.e. 169 BGA) assembled. 5 of them work fine. The other 6 eventually loose debugging connection. It doesn't happen immediatelly i.e. I'm still able to run a few lines of code but then it resets unrecoverable for the debug session (i.e. I have to restart the entire debug session. Soft reset doesn't work).

I can also measure the NRST (Pin H3) line that is pulled down caused by any internal mechanism (Unhandled interrupt?).

To investigate what line of code is causing the eventually occuring reset I started to place a "while(1);" and checked, if I still can pause and then run again without the debbugger loosing its connection.

This lead me to the following code section:

core_cm4.h

SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk |

SysTick_CTRL_TICKINT_Msk |

SysTick_CTRL_ENABLE_Msk;

Removing the "SysTick_CTRL_TICKINT_Msk" my "while(1);" after that line will continue to run without loosing debugging connection. Putting it back again I reach the "while(1);" but eventually it will break.

Now, this may still not be the root of cause. Starting a debugging session and pressing the soft reset button before I even run the program also makes the debugging session crash.

And just to mention again, it works on 5 boards. I.e. it can't really be a firmware issue. But what hardware failure could cause this issue with the above mentioned on the other 6 boards where the error pattern are all the same?

I do have about 10 years experience in the embedded environment dealing with uC quite a lot. But such a constellation I never faced before and causing my brain to blow up soon :face_with_steam_from_nose:.

Any one that may have an idea what is causeing that issue?

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Best answer by Uwe Bonnes

You are lucky:

it 27 nBOOT0: nBOOT0 option bit (this bit is reserved for STM32L47x/L48x devices)

0: nBOOT0 = 0

1: nBOOT0 = 1

Bit 26 nSWBOOT0: Software BOOT0 (this bit is reserved for STM32L47x/L48x devices)

0: BOOT0 taken from the option bit nBOOT0

1: BOOT0 taken from PH3/BOOT0 pin