nRF52 RESETREAS register

[Jason Wright]

I'm using an nRF52832 (QFAAB0) on a custom PCB, nRF5 SDK, S132 v2.0.

I'm occasionally encountering spontaneous resets and want to tract down the source. I found the RESETREAS register and the SDK function to access it (sd_power_reset_reason_get). However, I think either I'm not using it correctly or something's going wrong. I have this code in main():

uint32_t reset_reason;
sd_power_reset_reason_get(&reset_reason);
printf("Reset reason = 0x%08x\r\n", reset_reason);
sd_power_reset_reason_clr(0xFFFFFFFF);

However, this always prints out a register value that makes no sense to me: usually something like 0x99bdae6c, which would indicate a ton of reset reasons (including NFC field detect -- I don't have an antenna connected!)

Are there any issues with the RESETREAS register in this device, or are there any examples available for proper usage?

EDIT: I learned that the resets are probably happening because of the BLE advertisement window timing out (i.e. my APP_ADV_TIMEOUT_IN_SECONDS value), if this makes a difference. Still, I'd like to know how to get that reported in RESETREAS.

[RK]

Does the function return an error? Yes I know it's documented not to but if the softdevice isn't enabled, it still will. In that case it would not have updated &reset_reason which would be full of whatever junk was left on the stack at function entry.

Or just read the register yourself and write it yourself too.

uint32_t reset_reason = NRF_POWER->RESETREAS;
NRF_POWER->RESETREAS = 0xffffffff;

[Jason Wright]

Thanks for the replies, RK & Aryan. Based on this suggestion, I looked at the return value of sd_power_reset_reason_get, which was equal to 2 (NRF_ERROR_SOFTDEVICE_NOT_ENABLED). With that in mind, I realized that the issue is that I was calling the function before initializing the SoftDevice. I moved it below my call to ble_stack_init() and it now seems to be working fine. I would recommend adding this to the docs, which list the only possible return value for this function as NRF_SUCCESS.