Central can't find primary service successfully

Question

Hi,nordics 
 I failed to find primary service successfully .The sdk version is 10.00 and I reffered to the example is ble_app_uart_c_s120.The pripheral is a gamepad .I can connect to the gamepad successfully ,but I can't find the primary service .When the central start to find the primary service,I read the status of p_ble_gattc_evt->gatt_status and I find the value of p_ble_gattc_evt->gatt_status is BLE_GATT_STATUS_ATTERR_INVALID . Why this happened ?What can I do now ?I just want to communicate with the gamepad through the uuid .

Hung Bui · Accepted Answer

As you can find in Bluetooth Spec (Section 4.4.2 Vol 3 Part G Core spec v4.2) if there isn't any primary service match with the UUID you are looking for you will have Attribute not found error response back. Are you sure it's BLE_GATT_STATUS_ATTERR_INVALID not BLE_GATT_STATUS_ATTERR_ATTRIBUTE_NOT_FOUND ? 
 Make sure you match the UUID correctly, both the base UUID and service UUID. 
 I would suggest to use a sniffer and track what actually happens over the air.