nRF51822 sometimes won't respond to hardware reset

RE: nRF51822 sometimes won't respond to hardware reset

Hung Bui — Wed, 22 Jul 2015 10:46:02 GMT

From the laser marking, your chip is revision 3 chip and it should be able to get out of debug mode with a pin reset. But I'm not 100%sure about this, will confirm with R&D. Please let us know if you experience the issue again.

RE: nRF51822 sometimes won't respond to hardware reset

Nick Pelis — Tue, 21 Jul 2015 16:50:36 GMT

Thanks for the response @Hung Bui. I figured it was a momentary electrical glitch of some sort.

We will delete the external pullup resistor in the next version of the design, and add a pulldown on SWDCLK on your recommendation.

The markings on our chips say "NRF51822 CFACA0 1452AE".

RE: nRF51822 sometimes won't respond to hardware reset

Hung Bui — Mon, 20 Jul 2015 12:55:14 GMT

@Nick Pelis: I am suspecting that you chip might accidentally enter debug mode, maybe because of an ESD pulse happens on the SWDCLK pin.

Why do you have 100k pullup on the nRRST line ? There is already a 12k pull up internally. I would suggest you to try adding a pull down resistor on the SWDCLK pin to have more resistance over ESD, try 470 Ohm. The draw back will be it could be harder for the programmer to flash the chip.

Also please let me know your chip version (laser marking). On our chip version 3 you should be able to trigger a pin reset when in debug mode.