RE: How do I know that characteristic has been subscribed to?

Garret — Thu, 01 Dec 2016 14:06:13 GMT

Why won't SES ide follow the event definitions back to their base. If I right click on BLE_GATTS_EVT_WRITE and select go to definition I get to BLE_GATTS_EVT_WRITE = BLE_GATTS_EVT_BASE, from this point I put the cursor over the BLE_GATTS_EVT_BASE and do the same right click, go to definition, but the ide won't take me to the definition of BLE_GATTS_EVT_BASE, Why?? Even more confusing is that I can search the entire project/solution and BLE_GATTS_EVT_BASE doesn't show up!! Even though the ble_gap.h and ble_gatt.h files show up as Dependencies in the project tree.

RE: How do I know that characteristic has been subscribed to?

Vebjørn — Wed, 04 Mar 2015 11:31:31 GMT

I agree that it is a bit difficult to find out which event an ID corresponds to, but you can find out like this:

Open ble_ranges.h and scroll down to #define BLE_EVT_BASE
Look at your event id (0x0050) and find out which range this lies in. Scrolling a bit down in ble_ranges.h we see that BLE_GATTS_EVT_BASE starts at 0x50 and stops at 0x6F, so the id is a GATTS event.
Open ble_gatts.h and find out where BLE_GATTS_EVT_BASE is used
We see that BLE_GATTS_EVT_WRITE is defined as BLE_GATTS_EVT_BASE (0x50) and the succeeding events are increments of this. (if your code was 0x53 you would have to count down along the enum declarations, and would arrive at BLE_GATTS_EVT_HVC).

So, what you are looking for in your switch-case is BLE_GATTS_EVT_WRITE. What happens when a device subscribes to a characteristic, it writes 1 to the characteristic CCCD handle. There are examples of catching this in most of the projects in the SDK. If you look in ble_app_hrs for example, you can see the following in the ble_hrs_on_ble_evt function:

 case BLE_GATTS_EVT_WRITE:
        on_write(p_hrs, p_ble_evt);
        break;

Then the on_write function checks if it is a write to the cccd handle:

 static void on_write(ble_hrs_t * p_hrs, 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 == p_hrs->hrm_handles.cccd_handle){
         on_hrm_cccd_write(p_hrs, p_evt_write);
      }
 }

and lastly the on_hrm_cccd_write function checks if notification has been enabled or disabled, and you can handle this acccordingly, in that function