/* p4_5.c C library Console I/O using USART2 at 9600 Baud
 *
 * This program demonstrates the use of C library console I/O.
 * The functions fputc() and fgetc() are implemented using
 * USART2_write() and USART2_read() for character I/O.
 * In the fgetc(), the received character is echoed and if a '\r'
 * is received, a pair of '\r', '\n' is echoed.
 * In fputc() and fgetc(), the file descripter is not checked. All
 * file I/O's are directed to the console.
 *
 * By default, the clock is running at 8 MHz.
 * The USART is configured for 9600 Baud.
 * PA2 - USART2 TX (AF1)
 * PA3 - USART2 RX (AF1)
 * Use Tera Term on the host PC to send keystrokes and observe the display
 * of the characters echoed.
 *
 * This program was tested with Keil uVision v5.23 with DFP v2.0.0
 */
#include "stm32F0xx.h"
#include <stdio.h>

void USART2_init(void);
void delayMs(int);
int USART2_write(int c);
int USART2_read(void);

int main(void) {
    int n;
    char str[80];

    USART2_init();

    printf("Test stdio library console I/O functions\r\n");
    fprintf(stdout, "    test for stdout\r\n");
    fprintf(stderr, "    test for stderr\r\n");

    while (1) {
        printf("please enter a number: ");
        scanf("%d", &n);
        printf("the number entered is: %d\r\n", n);
        printf("please type a character string: ");
        gets(str);
        printf("the character string entered is: ");
        puts(str);
        printf("\r\n");
    }
}

/* initialize USART2 to transmit at 9600 Baud */
void USART2_init (void) {
    RCC->AHBENR |= RCC_AHBENR_GPIOAEN;          /* Enable GPIOA clock */
    RCC->APB1ENR |= RCC_APB1ENR_USART2EN;    /* Enable USART2 clock */

    /* Configure PA2, PA3 for USART2 TX, RX */
    GPIOA->AFR[0] &= ~0xFF00;
    GPIOA->AFR[0] |=  0x1100;   /* alt1 for USART2 */
    GPIOA->MODER  &= ~0x00F0;
    GPIOA->MODER  |=  0x00A0;   /* enable alt. function for PA2, PA3 */

    USART2->BRR = 0x0341;       /* 9600 baud @ 8 MHz */
    USART2->CR1 = 0x000C;       /* enable Tx, Rx, 8-bit data */
    USART2->CR2 = 0x0000;       /* 1 stop bit */
    USART2->CR3 = 0x0000;       /* no flow control */
    USART2->CR1 |= 0x0001;      /* enable USART2 */
}

/* Write a character to USART2 */
int USART2_write (int ch) {
    while (!(USART2->ISR & 0x0080)) {}   // wait until Tx buffer empty
    USART2->TDR = (ch & 0xFF);
    return ch;
}

/* Read a character from USART2 */
int USART2_read(void) {
    while (!(USART2->ISR & 0x0020)) {}   // wait until char arrives
    return USART2->RDR;
}

/* The code below is the interface to the C standard I/O library.
 * All the I/O are directed to the console, which is UART3.
 */
struct __FILE { int handle; };
FILE __stdin  = {0};
FILE __stdout = {1};
FILE __stderr = {2};

/* Called by C library console/file input
 * This function echoes the character received.
 * If the character is '\r', it is substituted by '\n'.
 */
int fgetc(FILE *f) {
    int c;

    c = USART2_read();      /* read the character from console */

    if (c == '\r') {        /* if '\r', after it is echoed, a '\n' is appended*/
        USART2_write(c);    /* echo */
        c = '\n';
    }

    USART2_write(c);        /* echo */

    return c;
}

/* Called by C library console/file output */
int fputc(int c, FILE *f) {
    return USART2_write(c);  /* write the character to console */
}