Proxmark3 community

LuckyD1ce

Contributor

Registered: 2020-10-23

Posts: 6

Proxmark3 reboots after ~30 seconds

Hey guys,

i am currently working with the Proxmark3 and implemented my own functions in order to gather data from a card. Therefore, i need to calculate some ECDH stuff with the provided mbedtls functions.
My problem is, that after ~30 seconds, the proxmark3 reboots during the calculation. This means, i can't get past a certain point and never get the result in order to send it to the card afterwards.
I read in another thread, that it could be a "watchdog" protection. While computing these values, the proxmark isn't communicating with the card. Could that be the case the communication stops?
I hope it is not some kind of power consumption or RAM error.

Thanks in advance.

Kind regards,
Robin

gator96100

Contributor

From: Austria

Registered: 2016-03-25

Posts: 177

Re: Proxmark3 reboots after ~30 seconds

If you have a JTAG debugger you can use the hardware debugging feature of the Proxmark. It does help finding that kind of bugs.
I’m not sure if the watchdog is enabled, but you can try to disable it.

If I’m not mistaken to disable it:

AT91C_BASE_WDTC->WDTC_WDMR = AT91C_WDTC_WDDIS;

Or call

WDT_HIT();

to reset the watdchog

LuckyD1ce

Contributor

Registered: 2020-10-23

Posts: 6

Re: Proxmark3 reboots after ~30 seconds

Thank you very much!

I used the first command to disable the watchdog at the start of my function. After that, it would compute everything without rebooting.

iceman

Administrator

Registered: 2013-04-25

Posts: 9,538

Website

Re: Proxmark3 reboots after ~30 seconds

... there is a reason for WDT_HIT();

The recommended usage is to make sure to call it in the beginning of long running fcts or loops.
I suggest you don't deviate from that.

LuckyD1ce

Contributor

Registered: 2020-10-23

Posts: 6

Re: Proxmark3 reboots after ~30 seconds

Sorry for the late reply.

First, I implemented everything with the WDT_HIT() command and it works properly.
Now, i have a final problem. I try to measure the time it takes to communicate with an Iso 14443a smartcard. I use the StartCountUS() timer, but if I start the timer before sending the APDU, the proxmark disconnects again during the WTX response part during the communication. Here the link to the part in the code (Proxmark3 Git repo).

I don't think the watchdog is the problem, because i even called WDT_HIT() in the loop, but it still disconnected.

Has anyone a suggestion for this problem? It seems like the timer is too much to handle in this case (otherwise, the timer works fine and without timer, the communication works too)

Kind regards