uart.c

#include <msp430.h>
#include <stddef.h>
#include <stdint.h>
#include "printf.h"

void uart_init(void)
{
    P1SEL = BIT1 + BIT2;  /* P1.1 = RXD, P1.2=TXD */
    P1SEL2 = BIT1 + BIT2; /* P1.1 = RXD, P1.2=TXD */

    /* USCI must be reset before configuration */
    if (UCA0CTL1 & UCSWRST) {
        /* Configure SMCLK as clock source */
        UCA0CTL1 |= UCSSEL_2;
        /* Configure baud rate to 9600 as it's the maximum baud rate the Launchpad allows.
         * Values are picked from the table in the family user guide (SLAU144).
         * PRESCALER = UCAxBR0 + (UCAxBR1 * 256) = 104 + 0 = 104
         * 1 MHZ / PRESCALER ~≃ 9600
         * 8-bit, no parity bit and one stop bit. */
        UCA0BR0 = 104;
        UCA0BR1 = 0;
        UCA0MCTL = UCBRS0;

        /* Reset the USCI */
        UCA0CTL1 &= ~UCSWRST;
    }
}

/* This is the internal function used by mpaland/printf (see external/printf) */
/* TODO: This is slow! Use buffering and interrupts? */
void _putchar(char character)
{
    /* Wait for the transfer buffer */
    while (!(IFG2 & UCA0TXIFG));

    /* Transmit the character */
    UCA0TXBUF = character;

    /* If we get a line-feed, add a carriage return to make new line work
     * properly on the other end. */
    if (character == '\n') {
        while (!(IFG2 & UCA0TXIFG));
        UCA0TXBUF = '\r';
    }
}

char uart_getchar()
{
    char chr = 0;

    /* Check if we have received anything */
    if (IFG2 & UCA0RXIFG) {
        chr = UCA0RXBUF;
    }

    return chr;
}