4.1.3 BLE Multirole Multilink Transparent UART

• 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

BLE_GAP_SetScanningEnable(true, BLE_GAP_SCAN_FD_ENABLE, BLE_GAP_SCAN_MODE_OBSERVER, 1000);

• BLE_GAP_EVT_ADV_REPORT event is generated upon finding Adverstisements 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 = 0x10;
        createConnParam_t.connParams.intervalMax = 0x10;
        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, we can start the advertisement to connect with another central device

  

• Add "APP_MSG_UART_CB" to the generated APP_MsgId_T

  

• 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 API

  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
  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()
  {
      // Send the data from UART to connected device through Transparent service
      BLE_TRSPC_SendData(conn_hdl[i], 1, &uart_data);
      i++;
      if(i==no_of_links) i = 0; //reset link index    
  }
   
    // Register call back when data is available on UART for Peripheral Device to send
    // 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);