RE: Update characteristic when no device is connected and beeing notified on notification enabled.

Matthias Sacher — Mon, 26 Feb 2018 07:55:29 GMT

Thank you for the answer.

I think the best way is to send it directly after the BLE_BAS_EVT_NOTIFICATION_ENABLED event.

RE: Update characteristic when no device is connected and beeing notified on notification enabled.

Sigurd — Fri, 23 Feb 2018 11:45:44 GMT

Hi,

If the central need the value immediately after the service discovery, and it don't want to wait for any notification, you could read the characteristic from the central directly. This is done in e.g. the central example ble_app_hrs_c in the SDK with ble_bas_c_bl_read().

Snippet:

case BLE_BAS_C_EVT_DISCOVERY_COMPLETE:
        {
            err_code = ble_bas_c_handles_assign(p_bas_c,
                                                p_bas_c_evt->conn_handle,
                                                &p_bas_c_evt->params.bas_db);
            APP_ERROR_CHECK(err_code);

            // Initiate bonding.
            err_code = pm_conn_secure(p_bas_c_evt->conn_handle, false);
            if (err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }

            // Batttery service discovered. Enable notification of Battery Level.
            NRF_LOG_DEBUG("Battery Service discovered. Reading battery level.");

            err_code = ble_bas_c_bl_read(p_bas_c);
            APP_ERROR_CHECK(err_code);

            NRF_LOG_DEBUG("Enabling Battery Level Notification.");
            err_code = ble_bas_c_bl_notif_enable(p_bas_c);
            APP_ERROR_CHECK(err_code);

Another option is to send the value with sd_ble_gatts_hvx() immediately after the central enables notification. Using the Battery Service as an example, in addition to starting a timer that sends notifications periodically, you could also send the value when you get the first BLE_BAS_EVT_NOTIFICATION_ENABLED event.

case BLE_BAS_EVT_NOTIFICATION_ENABLED:
// Start battery timer
err_code = app_timer_start(m_battery_timer_id, BATTERY_LEVEL_MEAS_INTERVAL, NULL);
APP_ERROR_CHECK(err_code);

//Add code with sd_ble_gatts_hvx() / ble_bas_battery_level_update()

break; // BLE_BAS_EVT_NOTIFICATION_ENABLED