Can a peripheral read a CCCD value?

RE: Can a peripheral read a CCCD value?

Turbo J — Sat, 29 Apr 2017 10:38:31 GMT

The latter method with the pointer cast could crash on NRF51x due to mis-alignment.

RE: Can a peripheral read a CCCD value?

Vyacheslav Lebets — Fri, 28 Apr 2017 20:07:10 GMT

You may use "uint16_decode()" function in app_util.h like this:

uint16_t aaa = uint16_decode(p_evt_write->data);

or:

uint16_t aaa = (uint16_t )*p_evt_write->data;

RE: Can a peripheral read a CCCD value?

pbirkner — Fri, 28 Apr 2017 19:46:46 GMT

Thanks! Still a bit confused tho. How can I actually read an integer value from p_evt_write->data ?

RE: Can a peripheral read a CCCD value?

Vyacheslav Lebets — Fri, 28 Apr 2017 18:39:13 GMT

Hi. First: CCCD is an abbreviation for Client Characteristic Configuration Descriptor. By writing the data to CCCD, the server allows the peripheral to make notifications or indications.

Second: You can read this value for example like this:

static void on_write(ble_evt_t* p_ble_evt)
{
    ble_gatts_evt_write_t* p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;
    if (p_evt_write->handle == YOUR_CHARACTERISTIC_HANDLE.cccd_handle)
    {
            /*
             then in "p_evt_write->data" we have cccd value
             and in "p_evt_write->len" we have value len, usually is 2 byte len.
            */
    }
}

And, of course, you may compare p_evt_write->data with 01:00 or 02:00.

Best, VL.