how to use sd_ble_gatts_service_changed()

[Haruki Kawakami]

After updating an application on nRF51822 chip with a new application which has new Characteristic UUID via BLE, iOS app cannot detect the new Characteristic UUID. I know iOS device uses cache、so nRF51822 has to enable service changed characteristic. I already enable that like this.

ble_enable_params_t ble_enable_params;
ble_enable_params.gatts_enable_params.service_changed = IS_SRVC_CHANGED_CHARACT_PRESENT;
sd_ble_enable(&ble_enable_params);

and after disconnected, retrieve system attribute like this.

 err_code = sd_ble_gatts_sys_attr_get(m_conn_handle, 
                                                 m_service_changed_sys_attr, 
                                                 &sys_attr_len, 
                                                 BLE_GATTS_SYS_ATTR_FLAG_SYS_SRVCS);

then on next BLE_GAP_EVT_CONN_SEC_UPDATE event, set the system attribute and send service changed indication like this.

err_code = sd_ble_gatts_sys_attr_set(m_conn_handle,
                                             m_service_changed_sys_attr,
                                             sizeof(m_service_changed_sys_attr),
                                             BLE_GATTS_SYS_ATTR_FLAG_SYS_SRVCS);
 err_code = sd_ble_gatts_sys_attr_set(m_conn_handle,
                                             NULL,
                                             0,
                                             BLE_GATTS_SYS_ATTR_FLAG_USR_SRVCS);
 err_code = sd_ble_gatts_service_changed(m_conn_handle, 0x000C, 0xFFFF);

sd_ble_gatts_service_changed returns NRF_ERROR_INVALID_STATE error.

I can't find any idea or answer for this question. I already look in dfu_transport_ble.c's service_change_indicate(), but I can't solve the problem.

Thank you for your cooperation in advance.

[run_ar]

Was the service changed characteristic present when you first connected to the iOS device? If you added this later on when you altered the attribute table, iOS won't know about the service changed characteristic either.

[Haruki Kawakami]

run_ar yes, the service was present. so I'm worried...

[run_ar]

Which iOS version is this? And do you know if service changed indications was actually enabled in the first place?

[Haruki Kawakami]

the version I use is 8.1.3. yes I know that. but sd_ble_gatts_service_changed on BLE_GAP_EVT_CONN_SEC_UPDATE event return NRF_ERROR_INVALID_STATE.

[run_ar]

Could you capture an sniffer trace showing the initial bond so I can verify that service changed was actually enabled by the peer. Invalid state means that you are in an invalid connection state (not connected) or that indications was not enabled. Which softdevice version are you using (should be S110 v8 or a newer softdevice)?