How to increase BLE payload size

[ledi7]

Hi,

I am using the example ble_p2pServer_ota with STm32WBA55. I would send a packet between a client and a server with more than 20 bytes.

Here is part of the code from p2p_server.c:

When i debug the code, the value of Attr_Data_Length is correct until i send up to 20 bytes. If i want to send 25 bytes, the value of Attr_Data_Length remains at 20.

case ACI_GATT_ATTRIBUTE_MODIFIED_VSEVT_CODE:
        {
          /* USER CODE BEGIN EVT_BLUE_GATT_ATTRIBUTE_MODIFIED_BEGIN */
        	
          /* USER CODE END EVT_BLUE_GATT_ATTRIBUTE_MODIFIED_BEGIN */
          p_attribute_modified = (aci_gatt_attribute_modified_event_rp0*)p_blecore_evt->data;
          notification.ConnectionHandle         = p_attribute_modified->Connection_Handle;
          notification.AttributeHandle          = p_attribute_modified->Attr_Handle;
          notification.DataTransfered.Length    = p_attribute_modified->Attr_Data_Length;
          notification.DataTransfered.p_Payload = p_attribute_modified->Attr_Data;

 Then i cheched the value of ATT_MTU size in file app_config.h. This value is 251 which is correct.

#define CFG_BLE_ATT_MTU_MAX         (251)

Then i changed the default ATT_MTU size (minimum MTU value that GATT must support) from 23 to 50 in file ble_bufsize.h.

#define BLE_DEFAULT_ATT_MTU                  50 //23

 But nothing has changed. Can anyone help?

[STTwo-32]

Hello @ledi7 

To be able to send more then 20 bytes, you have to follow the Extended advertising feature. For more details, you may take a look at this Wiki. Also, the examples BLE_p2pClient_Ext and BLE_p2pServer_Ext may can help you to understand how to do that.

Best Regards.

STTwo-32