Need help with understanding sd_ble_gattc_hv_confirm input parameters

[Raja Sumant]

Let us say we have a struct

typedef struct
{
    uint16_t                    conn_handle;    /**< Handle of the current connection (as provided by the BLE stack, is BLE_CONN_HANDLE_INVALID if not in a connection).*/
    uint16_t                    service_handle; /**< Handle of Our Service (as provided by the BLE stack). */
    // OUR_JOB: Step 2.D, Add handles for the characteristic attributes to our struct
    ble_gatts_char_handles_t    char_handles;
    // Done with step 2.D
}ble_os_t;

Using this struct I have initialized a variable as

ble_os_t *p_our_service

Next I call the SoftDevice function to update a characteristic value (It has both notify and indicate turned on)

    char_md.char_props.notify   = 1;
    char_md.char_props.indicate = 1;
   


ble_gatts_hvx_params_t hvx_params;
  memset(&hvx_params, 0, sizeof(hvx_params));

  hvx_params.handle = p_our_service->char_handles.value_handle;
  hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;
  hvx_params.offset = 1;
  hvx_params.p_len  = &len;
  hvx_params.p_data = (uint16_t*)sensor_value;
  sd_ble_gatts_hvx(p_our_service->conn_handle, &hvx_params);
  err_code = sd_ble_gattc_hv_confirm(p_our_service->conn_handle, p_our_service->char_handles.value_handle);

I get a response that NRF_ERROR_INVALID_STATE for  sd_ble_gattc_hv_confirm.

Have I passed the parameters correctly or am I doing it wrong? Please help me out.

[Vidar Berg]

Hello,

sd_ble_gattc_hv_confirm() should only be called in response to the BLE_GATTC_EVT_HVX event on the client side as illustrated by the message sequence chart here: GATTC Handle Value Indication. This is why you get the NRF_ERROR_INVALID_STATE error in return.

[Raja Sumant]

Could you please help me on what the function will be by taking the example of this custom service tutorial:

https://devzone.nordicsemi.com/nordic/short-range-guides/b/bluetooth-low-energy/posts/ble-services-a-beginners-tutorial

?

Is it ble_our_service_on_ble_evt() ?

I have not understood the "in response to the BLE_GATTC_EVT_HVX event" part clearly.

It still gives me the same result. 

void ble_our_service_on_ble_evt(ble_evt_t const * p_ble_evt, void * p_context)
{
  	ble_os_t * p_our_service =(ble_os_t *) p_context;  
		// OUR_JOB: Step 3.D Implement switch case handling BLE events related to our service. 
         uint32_t            err_code;
         
         err_code = sd_ble_gattc_hv_confirm(p_our_service->conn_handle, p_our_service->char_handles.value_handle);
  //APP_ERROR_CHECK(err_code);
  //if(err_code=="NRF_SUCCESS")
  switch (err_code)
    {
        case NRF_SUCCESS:
        {
            cat = 1;
            NRF_POWER->SYSTEMOFF = 1;
        } break;
        case BLE_ERROR_INVALID_CONN_HANDLE:
        {
            cat = 2;
        } break;
        case NRF_ERROR_INVALID_STATE:
        {
            cat = 3;
           // NRF_POWER->SYSTEMOFF = 1;
        } break;
        case BLE_ERROR_INVALID_ATTR_HANDLE:
        {
            cat = 4;
        } break;
        default:
            cat = 5;
            break;

        }
  }

[Vidar Berg]

Yes, this will not work. The sd_ble_gattc_hv_confirm() shall only be used if you are implementing a GATT client that's going to be receiving indications from your custom service.

Could you provide some more background on what you are trying to achieve with this?

[Raja Sumant]

Hello Vidar.

I am trying to put my device to System off state as soon as the application reads a value.

For this, I want to check if the app has successfully read the data or not.

I have seen the nrf connect app detects both indication and notify from my firmware.

However what ever I do in the app does not change the response from NRF_ERROR_INVALID_STATE.

Please help me with it,

[Vidar Berg]

Hello,

Then you have go to system OFF when you receive the BLE_GATTS_EVT_HVC event (GATTS Handle Value Indication), or BLE_GATTS_EVT_HVN_TX_COMPLETE if you're sending it as a notification (GATTS Handle Value Indication).

Also, you can't access the POWER registers while the Softdevice is enabled. So you must use sd_power_system_off() call to enter System off instead of NRF_POWER->SYSTEMOFF = 1;

[Raja Sumant]

Hello Vidar,

Yes. I did the one with BLE_GATTS_EVT_HVC earlier but I noticed that this was causing a new issue of the value not being read by the app as I am entering the System off state a bit too soon.

I guess that is because I usedNRF_POWER->SYSTEMOFF = 1; .

sd_power_system_off() was not working for me and my system continued transmitting the characteristic.

Yesterday I found a way to over come this issue.

I have given a delay by reading the BLE_GATTS_EVT_HVC event twice and it worked fine.