Flash Storage not working in ble_evt_handler

[Ameer Usman]

My code bluetooth module hangs if I use flash storage functions inside the ble_evt_handler. I am using the functions from the fstorage example in peripheral folder.
I turned on debug, connected to module, updated the value and then it hangs and no matter what I do it does not return to normal, but the debug says that its still running. From the looks it does not even enter the ble_evt_handler (I know this from the Log command).

The code is below:

static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)  //This function here handles any event that comes, just add the event name and fill in what you want to do when the event occurs.
{
    ret_code_t err_code = NRF_SUCCESS;
    NRF_LOG_INFO("Got an Event!"); //To check if it comes here

    switch (p_ble_evt->header.evt_id) 
    {


        case BLE_GATTS_EVT_WRITE:  
        {
			nrf_fstorage_api_t * p_fs_api;
			p_fs_api = &nrf_fstorage_sd;

			#ifdef SOFTDEVICE_PRESENT
				NRF_LOG_INFO("SoftDevice is present.");
				NRF_LOG_INFO("Initializing nrf_fstorage_sd implementation...");
				/* Initialize an fstorage instance using the nrf_fstorage_sd backend.
				 * nrf_fstorage_sd uses the SoftDevice to write to flash. This implementation can safely be
				 * used whenever there is a SoftDevice, regardless of its status (enabled/disabled). */
				p_fs_api = &nrf_fstorage_sd;
			#else
				NRF_LOG_INFO("SoftDevice not present.");
				NRF_LOG_INFO("Initializing nrf_fstorage_nvmc implementation...");
				/* Initialize an fstorage instance using the nrf_fstorage_nvmc backend.
				 * nrf_fstorage_nvmc uses the NVMC peripheral. This implementation can be used when the
				 * SoftDevice is disabled or not present.
				 *
				 * Using this implementation when the SoftDevice is enabled results in a hardfault. */
				p_fs_api = &nrf_fstorage_nvmc;
			#endif

			err_code = nrf_fstorage_init(&fstorage, p_fs_api, NULL);
			APP_ERROR_CHECK(err_code);             

			NRF_LOG_INFO("Initializing nrf_fstorage_sd implementation...");

		   

			/* Let's write to flash. */
			NRF_LOG_INFO("Writing \"%x\" to flash.", p_data);
			err_code = nrf_fstorage_write(&fstorage, 0x3e100, &p_data, length, NULL);
			APP_ERROR_CHECK(err_code);
			
			//Waiting for operation to complete
			wait_for_flash_ready(&fstorage);
			NRF_LOG_INFO("Done.");
			
			//-----------------Testing - Reading----------------------
                char     m_hello_world[] = "hello world";
                err_code = nrf_fstorage_read(&fstorage, 0x3e100, m_hello_world, length);
                APP_ERROR_CHECK(err_code);

                NRF_LOG_INFO("Reading \"%x\" to flash.", m_hello_world);
                wait_for_flash_ready(&fstorage);
			//--------------------------------------------------------
			
		}
		
	}

If I comment out the flash storage function (write and read) it works as it should.

Any leads would greatly be appreciated. (Do lemme know if additional information is required)

Edit 1: If I run this program in the main before the while loop, it works fine but I require it in the run time.

This works fine:

int main(void)
{
    bool erase_bonds;

    log_init();
    timers_init();
    buttons_leds_init(&erase_bonds);
    power_management_init();
    ble_stack_init(); //Here the BLE stack is initialized
    adc_configure();  //ADC for checking the battery
    gap_params_init();
    gatt_init();
    advertising_init();   //Making the iBeacon packet and the Data (major minor UUID etc) into a structure and passing it
    db_discovery_init();  //Commented this AUAK
    services_init();    //Initializing the services
    conn_params_init();
    peer_manager_init();

    //-------------Flash!-----------------------------

    Flash_Test();
   
    //-----------------------------------------

    // Start execution.
    NRF_LOG_INFO("Beacon Start!.");
    advertising_start(erase_bonds);
    tx_power_set();

    // Enter main loop.
    for (;;)
    {   
        
        idle_state_handle();
    }
}

But does not work if I am using it in run-time (also tried to do it via raising a flag and executing the commands in timer but that did not work either.

[Hadi Deknache]

Hi Ameer,

My guess is that the flash storage functions are blocking in the event handler which therefore cause it to freeze. Generally events should be very short and call as few functions as possible in the event handler. A good idea would be to either add app_scheduler in you application or change a flag which you check in a loop if it has been changed and perform the function calls there.

/Hadi

[Ameer Usman]

I tried changing a flag that would initiate a snip in the main loop but the code seems to stay under

idle_state_handle();

So I am unable to run it in the main loop.

But I tried it in a timer, but again the program froze and gave no errors.

[Hung Bui]

I agree with Hadi. You shouldn't call fstorage init and especially wait_for_flash_ready() inside the event handler.

wait_for_flash_ready() is a blocking function and the MCU will stuck inside that event handler waiting for the fstorage event. But the event can't be handled because you are already on the same context priority so the event will not be fetched and you will end up in a dead loop. 

In stead you should check for the event inside fstorage_evt_handler(). 

[Hadi Deknache]

Do you check the flag inside the loop? I assume that the code you posted above on main is not the one you used?

e.g., 

for (;;)
{   
    if(flash_ready)
    {
        flash_Test(); 
    }
    
    idle_state_handle();
}

EDIT:

Does the code also freeze if you call these in the ble_evt_handler

err_code = nrf_fstorage_init(&fstorage, p_fs_api, NULL);
APP_ERROR_CHECK(err_code);             

NRF_LOG_INFO("Initializing nrf_fstorage_sd implementation...");

/* Let's write to flash. */
NRF_LOG_INFO("Writing \"%x\" to flash.", p_data);
err_code = nrf_fstorage_write(&fstorage, 0x3e100, &p_data, length, NULL);
APP_ERROR_CHECK(err_code);

and then perform the next read function calls in the fstorage_evt_handler when it triggers NRF_FSTORAGE_EVT_WRITE_RESULT and vice versa

/Hadi

[Ameer Usman]

No its not working even when i secluded it from the ble_evt_handler.

Any further information I can provide regarding this for diagnosis?