BLE custom characteristics values are getting reset on a board power cycle in NRF52832

[Srivisakh]

Hi,

I am working on NRF52832 board in segger embedded studio. I am using nrf SDK 15.0.0.

I have created BLE custom characteristics and using nrfConnect mobile app to communicate with the Nordic board. On a power cycle, the custom characteristics values are getting reset. Can you please guide me on how to use a non-volatile storage and use the softe device APIs so that the custom characteristics can be restored with the previous values on a power cycle.

It would be nice if you suggest me any SDK example code for this case so that I can refer to it.

[awneil]

Srivisakh said:

On a power cycle, the custom characteristics values are getting reset

Of course they are: RAM is volatile, so  anything stored in RAM is going to be lost over a power cycle!

https://devzone.nordicsemi.com/f/nordic-q-a/45606/getting-hex-values-for-entering-numeric-values/187663#187663

So, if you want anything to be retained over a power cycle, you need some sort of non-volatile storage.

The same applies to any microcontroller - it is not specific to Nordic or to BLE Characteristic values.

The Nordic SDK provides the following to use the nRF52's Flash for non-volatile data storage:

Flash Data Storage (FDS) : https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.3.0/lib_fds.html

Flash Storage: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.3.0/lib_fstorage.html (this is the low-level driver used by FDS)

SDK Examples are linked from the above pages.

[Srivisakh]

Thanks for the fast response Awnell. 
I am able to store the characteristic value in flash memory. Now my query is that how to give those data to the custom characteristics on a power cycle. In another words, which soft device API should I use to give the stored value to custom characteristics?
I got a clue from the below link like "sd_ble_gatts_value_set()" in the below link 
https://devzone.nordicsemi.com/f/nordic-q-a/19759/most-efficient-smart-way-of-persisting-characteristic-values-on-nrf52

[awneil]

Srivisakh said:

Now my query is that how to give those data to the custom characteristics on a power cycle. In another words

In exactly the same way that you set them up in the first place!

It's just a matter of taking the values that you read from Flash instead of hard-coding them in your source code!

[Srivisakh]

Thanks for the reply Awneil. One small clarification : Values for the custom characteristics are being input through nrfConnect mobile app and these values only I need to store in flash memory.

[Srivisakh]

Hi,
I am trying to use sd_ble_gatts_value_set() as a part of on_connect() function. on_connect() will be called when any android phone is attempting to connect to the server. 

I am using sd_ble_gatts_value_set() and assigned the gatt_value from flash memory, so that the handle will be getting the value even after power cycle. But I am getting NRF_ERROR_INVALID_ADDR error after sd_ble_gatts_value_set() function.

What can be the reason. Please help and please heads up if my understading about the sd_ble_gatts_value_set() is wrong or not.

[Amanda Hsieh]

Hi, 

Please see this post. 

-Amanda

[Srivisakh]

Thanks for the reply. 
I was able to save the BLE data in flash memory and retrieve the data using sd_ble_gatts_value_set() function, and on a power cycle, the custom characteristics were restored.

Right now, I have a clarification like, instead of storing this data in flash memory and retrieving using sd_ble_gatts_value_set(), can I use the bonded information functionality in this case to store and retrieve.