Quick Start Guide for USART STDIO Integration

This guide shows how to use the STDIO Serial API on top of the Serial Interface service, so printf() and scanf() use a USART/UART as console I/O.

What STDIO Does

The STDIO serial layer connects C standard I/O (printf, putchar, scanf, getchar) to ASF serial functions. Internally, stdio_serial_init() binds stdio to usart_serial_putchar() / usart_serial_getchar().

Basic use case - USART console with printf/scanf

In this use case:

• A USART/UART is configured with usart_serial_options_t
• stdio_serial_init() binds that peripheral to stdio
• The application prints a banner and echoes received characters

Setup steps

Prerequisites

1. Serial Interface service
2. STDIO serial API
3. Board pin mux configured for the selected console peripheral
4. conf_uart_serial.h (or equivalent) with baud/parity/format macros

Example code

#include <asf.h>
#include <stdio_serial.h>
#include <conf_uart_serial.h>
 
static const usart_serial_options_t stdio_options = {
    .baudrate = CONF_UART_BAUDRATE,
    .charlength = US_MR_CHRL_8_BIT,
    .paritytype = CONF_UART_PARITY,
    .stopbits = US_MR_NBSTOP_1_BIT,
};
 
int main(void)
{
    uint32_t ch;
 
    sysclk_init();
    board_init();
 
    stdio_serial_init(CONF_UART, &stdio_options);
 
    printf("\\n\\rUSART STDIO ready\\n\\r");
 
    while (1) {
        scanf("%c", (char *)&ch);   // blocking read
        printf("%c", (char)ch);     // echo back
    }
}

Workflow

1. Initialize clocks with sysclk_init()
2. Initialize pins/board with board_init()
3. Fill usart_serial_options_t with baud and frame format
4. Call stdio_serial_init(CONF_UART, &stdio_options)
5. Use printf() / scanf() in the main loop

Notes

• scanf()/getchar() are blocking unless you add your own non-blocking logic.
• For SAM targets, CONF_UART usually maps to CONSOLE_UART in conf_uart_serial.h.
• Reference example: common/utils/stdio/stdio_serial/stdio_serial_example/stdio_serial_example.c