GATT services discovery

[Anonymous]

I'm trying to get data from a custom GAP peripheral, GATT server.
The peripheral sent data, and I can read GATT DB from CySmart, of course the services are unknown, but the data can be read and write.
Now, starting from PSoC_4_BLE_Central_IAS example, I try to read the same data.
•    After the call back function initialization CyBle_Start(StackEventHandler) and CyBle_ProcessEvents(); I manage the events I scan for device CyBle_GapcStartScan(CYBLE_SCANNING_FAST);  
•    and after the CYBLE_EVT_GAPC_SCAN_PROGRESS_RESULT I get advertising data from evetparameter pointer.
•    Found my device, I connect it by CyBle_GapcConnectDevice(&connectPeriphDevice);
•    did this, I start GATT discovery calling  CyBle_GattcStartDiscovery(connHandle) that does not return any event parameter (the documentation says this) and
•    I need to discover my GATT services and attributes. I've used CyBle_GattcDiscoverAllPrimaryServices(connHandle); and CYBLE_EVT_GATTC_DISCOVERY_COMPLETEe event are generated
from here  I'm not understand how continue.
Where are the discovered services?
Does CYBLE_EVT_GATTC_DISCOVERY_COMPLETE returns an evetparameter? (reading the BLE documentation, this is not clear).
The examples on central function are very few, Can I have some help?

   

Thanks, Fabrizio

[Anonymous · Accepted solution]

Hi,

   

After you call the GattcDiscoverAllPrimaryServices API, you will get the discovery data in chunks called (group) from the peripheral. Each time you receive a group, you will get the CYBLE_EVT_GATTC_READ_BY_GROUP_TYPE_RSP. You can obtain the data from the event parameter when you get this event. After all the discovery data is sent in multiple CYBLE_EVT_GATTC_READ_BY_GROUP_TYPE_RSP events, you will finally get the CYBLE_EVT_GATTC_DISCOVERY_COMPLETE event.

   

I have attached a Central / Clinet project which discovers all primary services and characteristics from a server and displays them.

   

Please find it attached. Use a UART Serial terminal (Like teraterm / coolterm) to test the project.

   

Regards,

   

- Madhu Sudhan

[Anonymous]

Thanks Madhu, your help is helpful, but it generates, to me, some doubts and I need to understand.

   

On my previous try I've used, after the connection, the CyBle_GattcStartDiscovery() function with the return of CYBLE_EVT_GATTC_DISCOVERY_COMPLETE event.
Then I've called CyBle_GattcDiscoverAllPrimaryServices() and  waited the CYBLE_EVT_GATTC_READ_BY_GROUP_TYPE_RSP event, that never appeared.
This seemed the right way. On my opinion.

   

In your example CyBle_GattcStartDiscovery() was never used, instead after the connection, if I've correctly interpreted your code,  you call CyBle_GattcDiscoverAllPrimaryServices() and other.

   

I've done the same and I've received CYBLE_EVT_GATTC_READ_BY_GROUP_TYPE_RSP,  two time, and CYBLE_EVT_GATTC_ERROR_RSP at the end, so this indicates that I've two services (not yet analyzed).

   

My question is: why CyBle_GattcStartDiscovery() doesn't return what I expected? What is the use of CyBle_GattcStartDiscovery()?

   

Regards, Fabrizio

[Anonymous]

The CyBle_GattcStartDiscovery() function has the following listed in the documentation (under BLE_gatt.c where "BLE" is the name of you bluetooth component):

   

/****************************************************************************** 
* Function Name: CyBle_GattcStartDiscovery
***************************************************************************//**
* 
*  Starts the automatic server discovery process. Two events may be generated 
*  after calling this function - CYBLE_EVT_GATTC_DISCOVERY_COMPLETE or 
*  CYBLE_EVT_GATTC_ERROR_RSP. The CYBLE_EVT_GATTC_DISCOVERY_COMPLETE event is 
*  generated when the remote device was successfully discovered. The
*  CYBLE_EVT_GATTC_ERROR_RSP is generated if the device discovery is failed.
* 
*  \param connHandle: The handle which consists of the device ID and ATT connection ID.
* 
* \return
*    CYBLE_API_RESULT_T : Return value indicates if the function succeeded or
*                        failed. Following are the possible error codes.
*
*   <table>    
*   <tr>
*      <th>Errors codes</th>
*      <th>Description</th>
*    </tr>
*    <tr>
*      <td>CYBLE_ERROR_OK</td>
*      <td>On successful operation</td>
*    </tr>
*    <tr>
*      <td>CYBLE_ERROR_INVALID_PARAMETER</td>
*      <td>'connHandle' value does not represent any existing entry.</td>
*    </tr>
*    <tr>
*      <td>CYBLE_ERROR_INVALID_OPERATION</td>
*      <td>The operation is not permitted</td>
*    </tr>
*   <tr>
*      <td>CYBLE_ERROR_MEMORY_ALLOCATION_FAILED</td>
*      <td>Memory allocation failed</td>
*    </tr>
*   <tr>
*      <td>CYBLE_ERROR_INVALID_STATE</td>
*      <td>If the function is called in any state except connected or discovered</td>
*    </tr>
*   </table>
* 
******************************************************************************/