retarget.h

/**********************************************
 * 
 * This simple library is used to redirect
 * functions like printf(), scanf(), putchar()
 * among other to the UART output on the STM32
 * using HAL.
 * 
 * Credits to the book Mastering STM32
 * File by Benjamin Calderon 2017
 * 
 ***********************************************/


#include "stm32l0xx_hal.h"
#include "usart.h"
#include <errno.h>
#include <sys/stat.h>
#include <stdio.h>

#define STDIN_FILENO 0
#define STDOUT_FILENO 1
#define STDERR_FILENO 2

UART_HandleTypeDef *gHuart;

void RetargetInit(UART_HandleTypeDef *huart) {
    gHuart = huart;

    setvbuf(stdout, NULL, _IONBF, 0);
}

int _isatty(int fd) {
    if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
        return 1;
    
    errno = EBADF;
    return 0;
}

int _write(int fd, char* ptr, int len) {
    HAL_StatusTypeDef hstatus;
    
    if (fd == STDOUT_FILENO || fd == STDERR_FILENO) {
        hstatus = HAL_UART_Transmit(gHuart, (uint8_t *) ptr, len, HAL_MAX_DELAY);
        if (hstatus == HAL_OK)
            return len;
        else
            return EIO;
    }
    errno = EBADF;
    return -1;
}

int _lseek(int fd, int ptr, int dir) {
    (void) fd;
    (void) ptr;
    (void) dir;

    errno = EBADF;
    return -1;
}

int _read(int fd, char* ptr, int len) {
    HAL_StatusTypeDef hstatus;

    if (fd == STDIN_FILENO) {
        hstatus = HAL_UART_Receive(gHuart, (uint8_t *) ptr, 1, HAL_MAX_DELAY);
        if (hstatus == HAL_OK)
            return 1;
        else
            return EIO;
    }
    errno = EBADF;
    return -1;
}

int _fstat(int fd, struct stat* st) {
    if (fd >= STDIN_FILENO && fd <= STDERR_FILENO) {
        st->st_mode = S_IFCHR;
    }
    errno = EBADF;
    return -1;
}