/* Name: uart.c * Project: AVR USB driver for CDC interface on Low-Speed USB * Author: Osamu Tamura * Creation Date: 2006-06-18 * Tabsize: 4 * Copyright: (c) 2006 by Recursion Co., Ltd. * License: Proprietary, free under certain conditions. See Documentation. *
 * 2006-07-08   adapted to higher baud rate by T.Kitazawa
 *//*General Description:    This module implements the UART rx/tx system of the USB-CDC driver.Note: This module violates the rule that interrupts must not be disabled forlonger than a couple of instructions (see usbdrv.h). Running UART interrupthandlers with sei as the first instruction is not possible because it wouldrecurse immediately (the cause of the interrupt has not been removed). Ifwe collect the data and then call sei(), we win little. We therefore decideto violate the rule. The effect on USB operation is, that packages may belost. This is equivalent to a package being dropped due to a CRC error. Thehost will therefore retry the transfer after a timeout. It is therefore verylikely that no effect is seen at the application layer.*/#include <avr/io.h>#include <avr/interrupt.h>#include <avr/pgmspace.h>   /* needed by usbdrv.h */#include "oddebug.h"#include "uart.h"#include "usbdrv.h"         /* only for usbWord_t */#if UART_CFG_HAVE_USART/* UART buffer */uchar    urptr, uwptr, irptr, iwptr;uchar    rx_buf[RX_SIZE], tx_buf[TX_SIZE];#ifndef URSEL#   define URSEL_MASK   0#else#   define URSEL_MASK   (1 << URSEL)#endifvoid uartInit(ulong baudrate, uchar parity, uchar stopbits, uchar databits){usbDWord_t   br;    br.dword = F_CPU / (8L * baudrate) - 1;	UCSR0A  |= (1<<U2X0);
#if DEBUG_LEVEL < 1    /*    USART configuration    */    UCSR0B  = 0;    UCSR0C  = URSEL_MASK | ((parity==1? 3:parity)<<UPM00) | ((stopbits>>1)<<USBS0) | ((databits-5)<<UCSZ00);    UBRR0L  = br.bytes[0];    UBRR0H  = br.bytes[1];#else    DBG1(0xf0, br.bytes, 2);#endif /* DEBUG_LEVEL */#ifdef USE_UART_RXD_INTERRUPT
    UCSR0B  = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0);
#else
    UCSR0B  = (1<<RXEN0) | (1<<TXEN0);
#endif
}void uartPoll(void){
	/* transmit */	if( uwptr!=irptr && (UCSR0A&(1<<UDRE0)) ) {
        UDR0    = tx_buf[irptr];        irptr   = (irptr + 1) & TX_MASK;    }
#ifndef USE_UART_RXD_INTERRUPT
	/* recieve */	if( UCSR0A&(1<<RXC0) ) {        uchar   status, data;        status  = UCSR0A;        data    = UDR0;        status  &= (1<<FE0) | (1<<DOR0) | (1<<UPE0);        if(status == 0) /* no receiver error occurred */            uartRxBufAppend( data );
    }
#endif
}uchar uartRxIsBusy(void){    return UCSR0A & (1<<RXC0);}#endif     /* UART_CFG_HAVE_USART */