5.1.3 BLE Multirole Multilink Transparent UART

• Include the user action. For more information, refer to User Action from Related Links.

• ble_trspc.h in app.c, BLE Transparent UART client related API's are available here

• ble_trsps.h in app.c, BLE Transparent UART Server related API's are available here

• osal/osal_freertos_extend.h in app_trsps_handler.c, OSAL related API's are available here

• definitions.h in all the files where UART will be used to print debug information

  Note: definitions.h is not specific to just UART peripheral, instead it should be included in all application source files where peripheral functionality will be exercised

// Scanning Enabled
BLE_GAP_SetScanningEnable(true, BLE_GAP_SCAN_FD_ENABLE, BLE_GAP_SCAN_MODE_OBSERVER, 1000);
// Output the status string to UART
SERCOM0_USART_Write((uint8_t *)"Scanning \r\n", 11);

• BLE_GAP_EVT_ADV_REPORT event is generated in app_ble_handler.c upon finding Advertisements on legacy channels

• BLE connection can be initiated by using the API BLE_GAP_CreateConnection(&createConnParam_t);

  // code snippet to filter scan results and initiate connection
    // Filter Devices based of Address, for this example address checking only 2 bytes
    if ((p_event->eventField.evtAdvReport.addr.addr[0] == 0xA1 && p_event->eventField.evtAdvReport.addr.addr[1] == 0xA2) ||
        (p_event->eventField.evtAdvReport.addr.addr[0] == 0xB1 && p_event->eventField.evtAdvReport.addr.addr[1] == 0xB2) ||
        (p_event->eventField.evtAdvReport.addr.addr[0] == 0xC1 && p_event->eventField.evtAdvReport.addr.addr[1] == 0xC2))
    {
        SERCOM0_USART_Write((uint8_t *)"Found Peer Node\r\n", 17);
        BLE_GAP_CreateConnParams_T createConnParam_t;
        createConnParam_t.scanInterval = 0x3C; // 37.5 ms
        createConnParam_t.scanWindow = 0x1E; // 18.75 ms
        createConnParam_t.filterPolicy = BLE_GAP_SCAN_FP_ACCEPT_ALL;
        createConnParam_t.peerAddr.addrType = p_event->eventField.evtAdvReport.addr.addrType;
        memcpy(createConnParam_t.peerAddr.addr, p_event->eventField.evtAdvReport.addr.addr, GAP_MAX_BD_ADDRESS_LEN);
        createConnParam_t.connParams.intervalMin = 0x30;
        createConnParam_t.connParams.intervalMax = 0x30;
        createConnParam_t.connParams.latency = 0;
        createConnParam_t.connParams.supervisionTimeout = 0x48;
        SERCOM0_USART_Write((uint8_t *)"Initiating Connection\r\n", 23);
        BLE_GAP_CreateConnection(&createConnParam_t);
    }

  

• The initiated scan operation will provide scan timeout event in app_ble_handler.c, we can start the advertisement to connect with another central device

  

• Add “APP_MSG_UART_CB” to the generated APP_MsgId_T in app.h.

  

• BLE_TRSPC_SendData(conn_hdl[i], 1, &uart_data); is the API to be used for sending data towards the Client device

• BLE_TRSPS_SendData(conn_hdl[i], 1, &uart_data); is the API to be used for sending data towards the Server device

  Note: * The precompiled application example uses a UART callback to initiate the data transmission upon receiving a character on UART.
  Example Implementation for Transmitting the received data over UART using the BLE_TRSPC_SendData and the BLE_TRSPS_SendData API in app.c.

  #define BLE_ROLE_CLIENT 1
  #define BLE_ROLE_SERVER 2
  uint16_t conn_hdl[3];// connection handle info captured @BLE_GAP_EVT_CONNECTED event
  uint8_t uart_data;
  uint8_t no_of_links;// No of connected peripheral devices
  uint8_t i = 0;// link index
  extern uint16_t conn_hdl_role[3];
  
  void uart_cb(SERCOM_USART_EVENT event, uintptr_t context)
  {
      APP_Msg_T   appMsg;   
      // If RX data from UART reached threshold (previously set to 1)
      if( event == SERCOM_USART_EVENT_READ_THRESHOLD_REACHED )
      {
          // Read 1 byte data from UART
          SERCOM0_USART_Read(&uart_data, 1);
  
          appMsg.msgId = APP_MSG_UART_CB;
          OSAL_QUEUE_Send(&appData.appQueue, &appMsg, 0);     
      }
  }
  
  void APP_UartCBHandler()
  {    
      uint8_t index = 0;
      for(index = 0; index < no_of_links; index++)
      {
          if(conn_hdl_role[index] != BLE_ROLE_CLIENT)
              BLE_TRSPS_SendData(conn_hdl[index], 1, &uart_data);
          else 
          {
              if(index == i)
                  BLE_TRSPC_SendData(conn_hdl[index], 1, &uart_data);
          }
      }   
      i++;
      if(i==no_of_links) i = 0; //reset link index    
  }
  
  ///////////////////////////////////////////////////////////////
  // Enable UART Read
  SERCOM0_USART_ReadNotificationEnable(true, true);
  // Set UART RX notification threshold to be 1
  SERCOM0_USART_ReadThresholdSet(1);
  // Register the UART RX callback function
  SERCOM0_USART_ReadCallbackRegister(uart_cb, (uintptr_t)NULL);
  
  /////////////////////////////////////////////////////////////
  if(p_appMsg->msgId==APP_MSG_BLE_STACK_EVT)
  {
      // Pass BLE Stack Event Message to User Application for handling
      APP_BleStackEvtHandler((STACK_Event_T *)p_appMsg->msgData);
  }
  else if(p_appMsg->msgId==APP_MSG_UART_CB)
  {
      // Transparent UART Client Data transfer Event
      APP_UartCBHandler();
  }