INVALID MEMORY ACCESS when writing to NRF_POWER->GPREGRET

[ishgum]

I am trying to write to NRF_POWER->GPREGRET to store some variables that should be retained through a software reset.

I am running SD 5, SDK 14 and using GCC to compile.

When I try to write to the register, i.e:

NRF_POWER->GPREGRET = 0x01

The program is halted by the error:

<error> app: SOFTDEVICE: INVALID MEMORY ACCESS

Printed out over UART.

Any thoughts on what is causing this error or how it could be solved?

[hmolesworth]

When using the SoftDevice I would recommend using the formal interface. With no SoftDevice installed your code would work fine. Worth a try :-)

uint32_t resultCode = sd_power_gpregret_set(0, 0x01);

// For specification see here:

/**@brief Set bits in the general purpose retention registers (NRF_POWER->GPREGRET*).
 *
 * @param[in] gpregret_id 0 for GPREGRET, 1 for GPREGRET2.
 * @param[in] gpregret_msk Bits to be set in the GPREGRET register.
 *
 * @retval ::NRF_SUCCESS
 */
SVCALL(SD_POWER_GPREGRET_SET, uint32_t, sd_power_gpregret_set(uint32_t gpregret_id, uint32_t gpregret_msk));

[Jørgen Holmefjord]

Hi,

Then the softdevice is enabled, access to some peripherals is blocked or restricted. The POWER peripheral have restricted access, which means it can be accessed through the softdevice API, as mentioned by @hmolesworth.

Best regards,
Jørgen

[ishgum]

Thanks! I suspected that this might be the case but couldn't find anything in the documentation.

[Aftab]

Hi,

I'm trying to do the same. In one of my custom BLE service, I'm calling this function: 

err_code = sd_power_gpregret_set(0, 0x01);

The project compiles successfully. But after setting this flag, if I power recycle the device, it does not boot into DFU mode, instead the default application (app) loads. Why writing the NRF_POWER->GPREGRET = 0x01 is not working here?

The app was previously loaded through DFU. I'm following this tutorial which successfully works uploading the firmware first time:

https://devzone.nordicsemi.com/b/blog/posts/getting-started-with-nordics-secure-dfu-bootloader

Regards.

[Jørgen Holmefjord]

Did you try setting the register to 0xB1? The tutorial say:

"we write to the retention register GPREGRET a flag (BOOTLOADER_DFU_START = 0xB1) and then we do a soft reset."