Board boots up with RESET button held low

cgnd_chris

I’m seeing some surprising behavior on the SparkFun Think Plus nRF9160 board and I’m wondering if it’s a bug or expected behavior.

If I hold the RESET button (causing the nRF9160 nRESET pin to be held at low at 0V), and plug in the USB cable, the board boots up and starts running the firmware. However, if I release the reset button and then press it again, the firmware stops running, and the board reboots when I release the reset button again.

It appears that the firmware will boot when power is initially applied to the board, irrespective of the state of the RESET pin. Is this expected behavior?

jaredwolff

Hey cgnd_chris

I think have seen this in the past. AFAIK it’s expected (I know it’s weird) but let me double check and get back to you.

jaredwolff

Just tried this again to confirm, and that is what I’m seeing here too on the B1A variant.

cgnd_chris

jaredwolff Thanks for double checking this. Do you happen to have the nRF91 dev kit? Do you see the same behavior on that board as well? I’m just curious if this is expected behavior for this chip, or due to something on the board itself. (I only have one of the Thing Plus boards, so I can’t check this out myself)

jaredwolff

Hmm seems like it’s working as expected on the DK. Curiously, there’s not much of a different between the two except for an RC filter. I’ll have to experiment a bit to get to a resolution for this. Thanks for pointing it out cgnd_chris

cgnd_chris

jaredwolff FYI, I already tried adding an RC filter (100nF/1kΩ) to the nRESET on the nRF91 (basically the same thing they have in the datasheet C10/R2). I didn’t notice any change in behavior with the RC added, but let me know if you see something different.

jaredwolff

Will do.