aci_gatt_update_char_value_ext issue

[APort]

Hello,

We are trying to use MTU larger than 24X bytes.

The characteristic size set to 483 bytes (CFG_BLE_MAX_ATT_MTU).

We tried to use aci_gatt_update_char_value_ext to set the value (as the HCI layer is limited to 255 bytes transfer).

aci_gatt_update_char_value_ext called twice (for both MPSs) , first part with 0 offset, and 2nd with 240.

First, Update_Type=GATT_CHAR_UPDATE_LOCAL_ONLY;  2nd call with GATT_CHAR_UPDATE_SEND_NOTIFICATION.

What happens is that random? number of bytes is sent (80).

If we always use GATT_CHAR_UPDATE_SEND_NOTIFICATION proper 480 bytes are sent, but twice (for both offset updates) ...

Thanks in advance

[STTwo-32 · Accepted solution]

Hello @APort 

What I understand, you are looking to send more data. So, I suggest you refer to this description:

1. Modify CFG_BLE_MAX_ATT_MTU to 512 in app_conf.h

2. Call aci_gatt_exchange_config() after connecting in app_ble.c:

tBleStatus status = aci_gatt_exchange_config(BleApplicationContext.BleApplicationContext_legacy.connectionHandle);

 3. Change Notify characteristic size in p2p_stm.c: 

aci_gatt_add_char(aPeerToPeerContext.PeerToPeerSvcHdle, UUID_TYPE_128, &uuid16,
                      CFG_BLE_MAX_ATT_MTU - 3, // [STM]
                      CHAR_PROP_NOTIFY, ATTR_PERMISSION_NONE,
                      GATT_NOTIFY_ATTRIBUTE_WRITE, /* gattEvtMask */
                      10, /* encryKeySize */
                      1, /* isVariable: 1 */
                      &(aPeerToPeerContext.P2PNotifyServerToClientCharHdle));

4. Change P2PS_STM_App_Update_Char function in p2p_stm.c:

tBleStatus P2PS_STM_App_Update_Char(uint16_t UUID, uint8_t *pPayload) 
{
  tBleStatus result = BLE_STATUS_INVALID_PARAMS;
  switch(UUID)
  {
    case P2P_NOTIFY_CHAR_UUID:
      
      aci_gatt_update_char_value_ext(0x0000,
                             aPeerToPeerContext.PeerToPeerSvcHdle,
                             aPeerToPeerContext.P2PNotifyServerToClientCharHdle,
                             0x00,
                             509,
                             0,
                             243,
                             (uint8_t *)  pPayload);
  

      aci_gatt_update_char_value_ext(0x0000,
                             aPeerToPeerContext.PeerToPeerSvcHdle,
                             aPeerToPeerContext.P2PNotifyServerToClientCharHdle,
                             0x00,
                             509,
                             243,
                             243,
                             (uint8_t *)  pPayload + 243);
  
      aci_gatt_update_char_value_ext(0x0000,
                             aPeerToPeerContext.PeerToPeerSvcHdle,
                             aPeerToPeerContext.P2PNotifyServerToClientCharHdle,
                             0x01,
                             509,
                             486,
                             23,
                             (uint8_t *)  pPayload + 486);    

      break;

    default:
      break;
  }

  return result;
}

View more

5. Modify P2PS_STM_Data_t structure in p2p_stm.h:

typedef struct
{
  uint8_t * pPayload;
  uint16_t     Length;
}P2PS_STM_Data_t; 

Best Regards.

STTwo-32