getting gatts value with nRF51822

[Morgan Redfield]

Hi There,

I want the functionality of my device to change when a value is written to a gatt characteristic. I've written an event handler that gets called whenever a write is made to the characteristic. This works correctly, but the problem is that I then can't get the value of the characteristic within this handler. I'm trying to use the sd_ble_gatts_value_get() function, and every time it is called the chip gets reset.

Thanks for any help you can give.

Here's my code:

void hex_evt_handler(ble_hex_t * p_hex, ble_hex_evt_t * p_ble_evt)
{

    uint32_t err_code = NRF_SUCCESS;

    uint8_t new_hex_status = 0;
    uint16_t len = sizeof(uint8_t);

    err_code = sd_ble_gatts_value_get(p_hex->hex_status_handles.value_handle,
	                                      0,
	                                      &len,
	                                      &new_hex_status);

    if (err_code != NRF_SUCCESS)
    {
        return;
    }

    ...
}

[Pål Håland]

Hi Morgan,

I don't know what the ble_hex_evt_t and ble_hex_t is.

The best way to get the data from the write event is doing this when receiving the ble_evt_t

switch (p_ble_evt->header.evt_id)
{
    case BLE_GATTS_EVT_WRITE:
        {
            uint8_t * p_data = p_ble_evt->evt.gatts_evt.params.write.data;
            uint16_t length = p_ble_evt->evt.gatts_evt.params.write.len;

            new_hex_status = p_data[0];
        }
        break;
    default:
        break;
}

Update 18.12.2015: Added pointer declaration to the p_data

[Morgan Redfield]

Hi Pal,

I made a service called ble_hex for my application, which is based around the battery measurement service. So ble_hex_evt_t and ble_hex_t are very similar to ble_bas_evt_t and ble_bas_t.

Thanks for your input about getting the value when receiving the ble_evt_t. I'll switch to that method of doing things.

I'm still wondering why the sd_ble_gatts_value_get() call was causing a crash. Any ideas about that?

[Maz Shar]

p_data definition should be like this right?

uint8_t * p_data = p_ble_evt->evt.gatts_evt.params.write.data;

[Pål Håland]

Yes, updated the answer with pointer declaration