Sawtooth on reset line

[akimata]

Hi,

Yesterday i was using my custom board with K22 microcontroller just fine. Today my board is not working at all

at first i had some hardfaults using code which was working just fine for atleast a month, then i could program it but i had weird messages about breakpoint at adress :0xffffff and my code didn't even start. After a while i can't even program it. I measured reset line and there is sawtooth signal there.

Some facts about my board:

NMI_b got external pullup

Reset_b got external pullup

Programming through SWD

I tried all sorts of kinetis unlock and erase_all_pin scripts when i could talk to uc and it didn't help, now i can't even communicate with board because of this reset i guess.

Any help would be appreciated

[jingpan]

Hi Grzegorz.

please check this document at first:

https://community.nxp.com/servlet/JiveServlet/download/857127-1-396709/Kinetis%20Lock%20issue%20anal... 

If all the method in the above document can't unlock it, your chip maybe damaged, then you need to refer to the document, and try a new chip.

Regards,

Jing

[akimata]

I tried almost every way to unlock kinetis and it didn't work, i got connection with the core but i'm unable to erase the kinetis. I attached some pictures.

Flashing and trying to debug code in MCUXPRESSO:

Connecting with core:

Attempt to erase the chip:

Unlock kinetis:

Any other ideas?

[jingpan]

Please check your hardware to see the power on sequence. Rest should later than power. If that is ok, please pull down reset and try all the software unlock way several times. If still not work, I think you have to replace the chip.

Regards,

Jing