5.2.1.1 Application Logic

To develop and run the application, follow these steps:

1. Open the main.c file of the project located in the ource files folder. Add the following code outside the main() function:

   #define RX_BUFFER_SIZE 1
   
   volatile bool SERCOM_1_readStatus = false;
   volatile bool SERCOM_1_writeStatus = false;
   
   volatile bool SERCOM_5_readStatus = false;
   volatile bool SERCOM_5_writeStatus = false;
   
   void SERCOM_1_WriteCallback(uintptr_t context)
   {
       SERCOM_1_writeStatus = true;
   }
   
   void SERCOM_1_ReadCallback(uintptr_t context)
   {
       SERCOM_1_readStatus = true;
   }
   
   void SERCOM_5_WriteCallback(uintptr_t context)
   {
       SERCOM_5_writeStatus = true;
   }
   
   void SERCOM_5_ReadCallback(uintptr_t context)
   {
       SERCOM_5_readStatus = true;
   } 
   

2. In the following code example, the read callback and write callback are declared. These functions set the pointer to a client function to be called when the given USART’s write or read event occurs. These callbacks describe the pointer to the function to be called when the write or read event has completed. By setting this to NULL, it can be disabled.

   

3. In Figure 5-17, SYS_Initialize (NULL) initializes the modules, such as ports, clock, SERCOM USART, Nested Vector Interrupt Controller (NVIC), and Non-Volatile Memory Controller (NVMCTRL). Also, the callback register functions for read and write operations are declared.
4. Inside the main() function, add the following code:

   /* Initialize all modules */
       SYS_Initialize ( NULL );
       
       // Extension SERCOM Read and Write Callback 
       SERCOM1_USART_ReadCallbackRegister(SERCOM_1_ReadCallback, 0);
       SERCOM1_USART_WriteCallbackRegister(SERCOM_1_WriteCallback, 0);
       
       // EDBG SERCOM Read and Write Callback 
       SERCOM5_USART_ReadCallbackRegister(SERCOM_5_ReadCallback, 0);
       SERCOM5_USART_WriteCallbackRegister(SERCOM_5_WriteCallback, 0);
       
       uint8_t rxBuffer; 
   

   

5. Start the implementation with a read request for SERCOM1 (for Extension) and SERCOM5 (for EDBG).

   // Read request for Extension 
       SERCOM1_USART_Read(&rxBuffer, RX_BUFFER_SIZE);
       
   // Read request for EDBG
       SERCOM5_USART_Read(&rxBuffer, RX_BUFFER_SIZE); 
   

   

6. In Figure 5-19, if the Extension is ready to read (Rx) the data (i.e., SERCOM_1_readStatus == true), then it transmits the received data to EDBG. And, if the Extension is ready to write (Tx) the data (i.e., SERCOM_1_writeStatus == true), then EDBG will start a read (Rx) request. Similarly, vice versa if the EDBG is ready to read (Rx) or if the EDBG is ready to write (Tx). Add the following code inside the while loop:

   if(SERCOM_1_readStatus == true)
           {
               SERCOM_1_readStatus = false;  
               
               //Transmit received bytes from EDBG
               SERCOM5_USART_Write(&rxBuffer, RX_BUFFER_SIZE);
           } 
   if(SERCOM_5_writeStatus == true)
           {
               SERCOM_5_writeStatus = false;
               SERCOM1_USART_Read(&rxBuffer, RX_BUFFER_SIZE);
           }
           
   if(SERCOM_5_readStatus == true)
           {
               SERCOM_5_readStatus = false; 
               
               //Transmit received bytes from Extension
               SERCOM1_USART_Write(&rxBuffer, RX_BUFFER_SIZE);
           }
           
   if(SERCOM_1_writeStatus == true)
           {
               SERCOM_1_writeStatus = false;
               SERCOM5_USART_Read(&rxBuffer, RX_BUFFER_SIZE);
           }