RAM retention problem

[enkavak]

Hello,

      I'm using nRF5 SDK with version 15, nRF52832 IC and softdevice s132. I need to save hold the data in the ram even in sleep mode. I'm using the below code. However it did not resolved my issue. 

 sd_power_ram_power_set(4,(POWER_RAM_POWER_S0POWER_On << POWER_RAM_POWER_S0POWER_Pos) |
    (POWER_RAM_POWER_S1POWER_On << POWER_RAM_POWER_S1POWER_Pos) |
    (POWER_RAM_POWER_S0RETENTION_On << POWER_RAM_POWER_S0RETENTION_Pos) |
    (POWER_RAM_POWER_S1RETENTION_On << POWER_RAM_POWER_S1RETENTION_Pos));

[Håkon Alseth]

Hi,

 

In WFE (or sd_app_evt_wait when using the softdevice) there is no need to change the RAM retention settings (assuming using reset values), as WFE will start executing based on where it previously was (just like any C function).

However, if using SystemOFF, then a wakeup will generate a reset condition, thus must of your states are reset. When using SystemOFF, it is not enough just to set the RAM retention in sleep, but you will also need to make sure that your firmware does not clear/overwrite your data at boot up. This is normally done by making a no-init/zero_init section.

Q1. Are you using Systemoff?

Q2: What compiler are you using?

 

Kind regards,

Håkon

[enkavak]

A1) I'm using Systemoff

A2) Segger Embedded studio

[Håkon Alseth]

Here's an example on how to retain a variable or section with systemoff/soft-reset for SES: ram_retention_softreset_clean.zip

To integrate this into your own project, please note the added section ".retained_section" in the flash_placement.xml file, as this must be added into your project.

 

Best regards,

Håkon

[enkavak]

For every variable do I need to define it like below for ram retention ?

uint32_t ram_value __attribute__((section(".retained_section"))) = 0;

[tesc]

That would be the case, yes.

[rakesh_hirur]

what about the size of the ".retained section" in placement file ? It is specified as "8" in "ram_retention_softreset_clean".  Is it 8 bytes or 8 RAM sections?

[strengthstrong]

#define __retention __attribute__((section("retention_mem_area0"), zero_init)) // essential

What do you need to add?