Quick start guide for USART module

This is the quick start guide for the USART module, with step-by-step instructions on how to configure and use the driver in a selection of use cases.

The use cases contain several code fragments. The code fragments in the steps for setup can be copied into a custom initialization function, while the steps for usage can be copied into, e.g., the main application function.

Basic use case - transmit a character

USART use cases

• Basic use case - transmit a character
• USART receive character and echo back

Basic use case - transmit a character

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

Setup steps

Prerequisites

1. System Clock Management

Example code

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

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 application C-file:

usart_putchar(USART_SERIAL, 'a');

Workflow

1. Send an 'a' character via USART

   • usart_putchar(USART_SERIAL, 'a');