What are the preconditions to read GPREGRET?

[geert_venken]

In my application I want to know if a DFU was executed successful and I'm using GPREGRET2 for it.

If a DFU as successful I'm writing  GPREGRET2:

      nrf_power_gpregret2_set(0x02);

In my application I read this register but get strange results, reading it the first time returns 0xE1, reading it a few moments later it returns the expected value 0x02;

See the Logging:

0015 [3] Application -> [00:00:02.368] T:xxxxxHsm Check DFU 1
0016 [0] DiagnosticMgr -> [00:00:02.368] T:xxxxxHsm Intern Check DFU
0017 [0] DiagnosticMgr -> [00:00:02.369] T:xxxxxHsm GPREGRET2 e1
0023 [3] Application -> [00:00:02.372] T:xxxxxHsm End Check DFU 1
0024 [3] Application -> [00:00:02.548] T:xxxxxHsm Check DFU 2
0025 [0] DiagnosticMgr -> [00:00:02.549] T:xxxxxHsm Intern Check DFU
0026 [0] DiagnosticMgr -> [00:00:02.549] T:xxxxxHsm GPREGRET2 2
0027 [0] DiagnosticMgr -> [00:00:02.550] T:xxxxxHsm !!!!!!!!!DFU performed CORRECTLY !!!!!!!!!!!!
0033 [3] Application     -> [00:00:02.553] T:xxxxxHsm     End Check DFU 2

Between the first read at 02.369 and the second read on 02.549, there are only 180ms.

Function the read the GPREGRET2 is:

sd_power_gpregret_get(1, &reg_val)

I want to read this RGPREGRET2 as soon as possible after the start up of the application as I want to base some initialization decisions on it.

I'm using nRF52833 with Softdevice S113 for BLE

Thanks

[Vidar Berg]

Hi,

The sd_power_gpregret_* APIs can only be used after the Softdevice is enabled. They will return with an error otherwise.

If you want to read the register before the softdevice is enabled, you can use the nrf_power_gpregret_get() function from nrf_power.h.

Best regards,

Vidar

[geert_venken]

Thanks Vidar,  

Indeed using the nrf_power API works. 

Looks like SoftDevice was the problem,  

[Vidar Berg]

Thanks for the update. Yes, these SD APIs allow the application to access peripherals that have been reserved by the SoftDevice (POWER in this case). This is not necessary when the SoftDevice is disabled. It's generally a good practice to check the return value when using SD APIs.

https://docs.nordicsemi.com/bundle/sds_s132/page/SDS/s1xx/sd_resource_reqs/hw_block_interrupt_vector.html