5.4.2.1 Application Logic

  1. Add the following macros and variables outside the main() function:
    #define RX_BUFFER_SIZE 1
#define TX_BUFFER_SIZE 1

volatile bool USART1_writeStatus = false;
volatile bool USART1_readStatus = false;

volatile bool USART0_writeStatus = false;
volatile bool USART0_readStatus = false;

uint8_t rxBuffer;
uint8_t txBuffer = 0xAA;
    Figure 5-57. Adding the Macros and Variables
  2. Add the RTS_ENABLE and RTS_DISABLE functions outside the main() function to manually control the RTS lines:
    void RTS_ENABLE(void)
{
    USART0_REGS->US_CR = US_CR_USART_RTSEN_Msk;
}
void RTS_DISABLE(void)
{
    USART0_REGS->US_CR = US_CR_USART_RTSDIS_Msk;
}
    Figure 5-58. Adding the RTS Functions
  3. Add event handlers and enable the hardware handshaking mode outside the main() function:
    void USART0_WriteEventHandler ( uintptr_t context )
{
    USART0_writeStatus = true;
}

void USART0_ReadEventHandler (uintptr_t context)
{
    RTS_ENABLE();
    USART0_readStatus = true;
}

void ext_usart_init()
{
    USART0_REGS->US_MR |= US_MR_USART_MODE_HW_HANDSHAKING;
}
    Figure 5-59. Adding Event Handlers
  4. Call the necessary functions and callback registers inside the main() function:
    SYSTICK_TimerStart();
ext_usart_init();
    
USART0_WriteCallbackRegister(USART0_WriteEventHandler, (uintptr_t)NULL);
USART0_ReadCallbackRegister(USART0_ReadEventHandler, (uintptr_t)NULL);
    
RTS_DISABLE();
USART0_Read(&rxBuffer, RX_BUFFER_SIZE);
    
USART0_Write(&txBuffer, TX_BUFFER_SIZE);
    Figure 5-60. Initialization of Modules
  5. Add the hardware handshaking configuration logic inside the while loop in the main() function:
    SYSTICK_DelayUs(500U);
if(USART0_writeStatus == true)
{
USART0_writeStatus = false;

//Transmit received bytes from EDBG
USART0_Write(&txBuffer, TX_BUFFER_SIZE);
}
        
if(USART0_readStatus == true)
{
USART0_readStatus = false;
            
//Receive transmitted bytes from EDBG
RTS_DISABLE();
USART0_Read(&rxBuffer, RX_BUFFER_SIZE);
}
    Figure 5-61. Adding the Application Logic
    Figure 5-62. SAM E70 Xplained Ultra – Hardware Handshaking Output