sw-uart.c

m8 usb to rs232

/* Name: sw-uart.c
 * Project: AVR USB driver for CDC interface on Low-Speed USB
 * Author: Osamu Tamura
 * Creation Date: 2006-06-22
 * Tabsize: 4
 * Copyright: (c) 2006 by Recursion Co., Ltd.
 * License: Proprietary, free under certain conditions. See Documentation.
 */

/*
General Description:
*/

#include <avr/io.h>
#include <avr/interrupt.h>
#include "oddebug.h"
#include "uart.h"

#if !UART_CFG_HAVE_USART

/* UART buffer */
uchar    urptr, uwptr, irptr, iwptr;
uchar    rx_buf[RX_SIZE], tx_buf[TX_SIZE];
uchar    tx_stage, bit_start;

void uartInit(int baudrate, uchar parity, uchar stopbits, uchar databits)
{

#if UART_CFG_INVERT
    UART_CFG_PORT   &= ~(1<<UART_CFG_TXD);
#else
    UART_CFG_PORT   |= (1<<UART_CFG_TXD);
#endif
    UART_DDR    |= (1<<UART_CFG_TXD);
    UART_DDR    &= ~(1<<UART_CFG_RXD);
    
    GIMSK    &= ~(1<<PCIE);
    TCCR0A   = 0;
    TCCR0B   = 0;

    OCR0A    =
    OCR1A    = (F_CPU/64L) / baudrate - 1;
    bit_start = 6 - (OCR1A>>1);
    TCCR0A   = 2;            /* CTC */
    TCCR1    = 0;
    TIMSK    = (1<<OCIE1A)|(1<<OCIE0A);

    PCMSK    = 1<<UART_CFG_RXD;   /*  PCINTn  */
    GIMSK    |= (1<<PCIE);

    tx_stage = 0;
}

void uartPoll(void)
{
    if( tx_stage==0 && OCR1C==0 && irptr!=uwptr ) {
        tx_stage = 10;
        OCR0B    = tx_buf[irptr];
        irptr    = (irptr+1) & TX_MASK;
        TCNT0    = 0;
        cli();
#if UART_CFG_INVERT
        UART_CFG_PORT   |= (1<<UART_CFG_TXD);       /* start bit */
#else
        UART_CFG_PORT   &= ~(1<<UART_CFG_TXD);       /* start bit */
#endif
        TCCR0B   = 3;         /* start timer0: 1/64 clk */
        sei();
    }
}

void uartStartTransmission(void)
{
    /* nothing to do -- we handle transmitter entirely in uartPoll() */
}

uchar uartRxIsBusy(void)
{
    return OCR1C;
}

#endif      /* UART_CFG_HAVE_USART */