EFM32 Flash protection AAP

[TonyBe]

Hi Folks,

I ran into a problem. My VC890 Multimeter had simply stopped working yesterday on the resistance and current mode. After checking the voltages on the PCB i quickly found the problem. One pin of the EFM32G230 MCU was shorted to VCC and at the same time measures 40R to Gnd(even when the MCU is off). Since this pin is externaly pulled down by the rotation switch in I and R mode, the Vcc is effectivly shorted to Gnd then. This results in a current draw of 150mA in all ranges and >500mA in resistance and current mode.

I've already ordered a new EFM32 chip for repair.
Since there is a SWD Debug Port on the pcb, i've tried to dump the flash with silabs commander. But well, you guessed it: the flash is locked via AAP.

Is there really no way to get an flash image when this protection is set? It would be a shame (and really bad for my wallet) if i must throw this 300€ Multimeter away with that kind of failure.
What happens when I manually connect with the chip (without the commander from silabs). Does the AAP protection covers the flash acces in hardware? Or is this like a flag which stops the debugger from reading flash. I couldn't find any information on how AAP exactly works.

Thank you all in advance
kind regards
Tony

[TonyBe]

..just a little extension to my initial post:

of course, if it would be possible to get the firmware binaries for the VC890 - my problem would be solved as well. The Meter is from Uni-T.. does somebody maybe has some connections there and can help me out?

Regards
Tony

[amyk]

Looks like you're not the first one...
https://www.eevblog.com/forum/repair/voltcraft-vc-890-by-uni-t-firmware/

You could spend 10x as much on an "MCU break" service to dump the firmware, but that's not really economical either. (If the DMM cost 10x or more, then that might even be a good way to do it.)

You could try some of the attacks like power glitching etc. if you have the time...

[TonyBe]

Hi together,

well yes. I've contacted goaty in the meantime and we chated a little bit. I'm currently trying to get in contact with Voltcraft support since my distri does not provide any information on how to contact them directly.
Maybe some of you allready had contact with Voltcraft?

I apologize for the bad structure this post here has. Very sorry for that,.. 

Kind regards