source: software/firmware/serial.c @ 5

#include <pic18fregs.h>
#include <stdio.h>
#include <my_serial.h>

char uart_txbuf[UART_BUFSIZE];
unsigned char uart_txbuf_prod;
volatile unsigned char uart_txbuf_cons;

PUTCHAR(c) /* Macro */
{
        unsigned char new_uart_txbuf_prod;
#if 0
        if  (!PORTBbits.RB7)
                return;
#endif
        new_uart_txbuf_prod = (uart_txbuf_prod + 1) & UART_BUFSIZE_MASK;
#if 1

again:
        while (new_uart_txbuf_prod == uart_txbuf_cons) {
                PIE1bits.TX1IE = 1; /* ensure we'll make progress */
        }
        uart_txbuf[uart_txbuf_prod] = c;
        uart_txbuf_prod = new_uart_txbuf_prod;
        PIE1bits.TX1IE = 1;
        if (c == '\n') {
                c = '\r';
                new_uart_txbuf_prod = (uart_txbuf_prod + 1) & UART_BUFSIZE_MASK;
                goto again;
        }
#else
again:
        while (!PIR1bits.TX1IF)
                ; /* wait */
        TXREG1 = c;
        if (c == '\n') {
                c = '\r';
                goto again;
        }
#endif
}

char
getchar(void)
{
        char c;
        while (!PIR1bits.RC1IF); /* wait for a char */
        c = RCREG1;
        if (RCSTA1bits.OERR) {
                RCSTA1bits.CREN = 0;
                RCSTA1bits.CREN = 1;
        }
        return c;
}