NRF_POWER->GPREGRET

[rshankle]

Hi Folks,

I am trying to get some data to persist past a reboot.  I noticed the ram_retention_pca1004 example  and it showed a simple assignment of:

NRF_POWER->GPREGRET = X

but when I do the following assignment (even before the reboot):

temp = NRF_POWER->GPREGRET;

temp is always 0.  (Needless to say the value is also zero after the power reset via watchdog timeout.)

I noticed in the example the following code:

#if defined(NRF52832_XXAA) || defined(NRF51422) || defined(NRF51822)
NRF_POWER->RAMON |= (POWER_RAMON_OFFRAM0_RAM0On << POWER_RAMON_OFFRAM0_Pos) |
(POWER_RAMON_OFFRAM1_RAM1On << POWER_RAMON_OFFRAM1_Pos);

Adding that didn't help, but I didn't expect it to as long as my assignment above keeps failing.

Is there a flag that needs to be set to use NRF_POWER->GPREGRET?

(I looked at using sd_power_gpregret_set but couldn't find the correct library to include, is that the correct solution?)

thanks, 
Bob

(Sorry for the basic question, just need some data to persist after a WDT reset.)

[awneil]

Yes, I think you do need to use sd_power_gpregret_set/get().

They are SoftDevice API calls - so you don't need any other special library.

Other than that, set a "no-init" area in RAM ...

https://devzone.nordicsemi.com/f/nordic-q-a/34395/status-of-sram-during-an-over-the-air-update/132658#132658

https://devzone.nordicsemi.com/f/nordic-q-a/42331/hi-i-am-using-segger-embedded-stodio-__no_init-not-work/164966#164966

[rshankle]

What is the connection between no-init and PREGRET?

I have the following code for testing:

void NVRAM_Test(void)
{
   uint32_t err_code;
   uint32_t gpregret_val = 0x00; 

   sd_power_gpregret_get(0, &gpregret_val);
   if(gpregret_val == 0xED){
        err_code = sd_power_gpregret_set(0, 0x00);
        APP_ERROR_CHECK(err_code);
   }
   else
   {
       err_code = sd_power_gpregret_set(0, 0xED);
       APP_ERROR_CHECK(err_code);
   }
}

When compiling I get:

undefined reference to `sd_power_gpregret_get'
undefined reference to `sd_power_gpregret_set'

thanks again for the help,

Bob

[awneil]

rshankle said:

What is the connection between no-init and PREGRET?

None at all - it's an alternative!

PREGRET is a specific hardware feature of the Nordic chip; no-init is applicable to any microcontroller.

rshankle said:

undefined reference to `sd_power_gpregret_get'
u

It should be in nrf_soc.h - along with all the other sd_power_ SoftDevice APIs.

Are you using a SoftDevice?

NB: How to properly post source code:

[rshankle]

The only thing in "nrf_soc.h" is "uint32_t sd_app_evt_wait(void);"

I'll look closer at this in the morning, thanks for the help.  (I'll work on properly posting code.)

thanks,

Bob

[Sigurd]

rshankle said:

The only thing in "nrf_soc.h" is "uint32_t sd_app_evt_wait(void);"

There are different versions of nrf_soc.h, depending on if you are using BLE/SoftDevice or not. When using an example that uses the S132 SoftDevice, the nrf_soc.h used can be found in the folder sdk_folder\components\softdevice\s132\headers.