USART receive character and echo back

In this use case, the USART module is configured for:

• Using USARTD0
• Baudrate: 9600
• Character length: 8 bit
• Parity mode: Disabled
• Stop bit: None
• RS232 mode

The use case waits for a received character on the configured USART and echoes the character back to the same USART.

Setup steps

Prerequisites

1. System Clock Management

Example code

1. The following configuration must be added to the project (typically to a conf_usart.h file, but it can also be added to your main application file.):

   #define USART_SERIAL                     &USARTD0
   #define USART_SERIAL_BAUDRATE            9600
   #define USART_SERIAL_CHAR_LENGTH         USART_CHSIZE_8BIT_gc
   #define USART_SERIAL_PARITY              USART_PMODE_DISABLED_gc
   #define USART_SERIAL_STOP_BIT            false

A variable for the received byte must be added:

uint8_t received_byte; 

Add to application initialization:

 sysclk_init();
 static usart_rs232_options_t USART_SERIAL_OPTIONS = {
    .baudrate = USART_SERIAL_BAUDRATE,
    .charlength = USART_SERIAL_CHAR_LENGTH,
    .paritytype = USART_SERIAL_PARITY,
    .stopbits = USART_SERIAL_STOP_BIT
 };
sysclk_enable_module(SYSCLK_PORT_D, PR_USART0_bm);
usart_init_rs232(USART_SERIAL, &USART_SERIAL_OPTIONS);

Workflow

1. Initialize system clock:

   • sysclk_init(); 

   • Note

     Not always required, but since the USART module (USART) driver is dependent on System Clock Management it is good practise to initialize this module.

2. Create USART options struct:

   • static usart_rs232_options_t USART_SERIAL_OPTIONS = {
        .baudrate = USART_SERIAL_BAUDRATE,
        .charlength = USART_SERIAL_CHAR_LENGTH,
        .paritytype = USART_SERIAL_PARITY,
        .stopbits = USART_SERIAL_STOP_BIT
     };

3. Enable the clock for the USART module:

   • sysclk_enable_module(SYSCLK_PORT_D, PR_USART0_bm); 

4. Initialize in RS232 mode:

   • usart_init_rs232(USART_SERIAL, &USART_SERIAL_OPTIONS);

Usage steps

Example code

Add to, e.g., main loop in application C-file:

received_byte = usart_getchar(USART_SERIAL);
usart_putchar(USART_SERIAL, received_byte);

Workflow

1. Wait for reception of a character:

   • received_byte = usart_getchar(USART_SERIAL); 

2. Echo the character back:

   • usart_putchar(USART_SERIAL, received_byte);