161 lines
3.4 KiB
C
161 lines
3.4 KiB
C
/*
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* uart_async.c
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*
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* This file is part of Triple-A library:
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* https://github.com/tuupola/triple-a
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*
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* Copyright 2011 Mika Tuupola
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*
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* Licensed under the MIT license:
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* http://www.opensource.org/licenses/mit-license.php
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*
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*/
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/* Based on Atmel Application Note AVR 306 */
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <stdio.h>
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#ifndef BAUD
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#define BAUD 9600
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#endif
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#include <util/setbaud.h>
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#ifndef UART_RX_BUFFER_SIZE
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#define UART_RX_BUFFER_SIZE 128
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#endif
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#ifndef UART_TX_BUFFER_SIZE
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#define UART_TX_BUFFER_SIZE 256
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#endif
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#if defined (UBRR0H)
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#warning Using UART0
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#define UBRRxH UBRR0H
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#define UBRRxL UBRR0L
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#define UCSRxA UCSR0A
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#define U2Xx U2X0
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#define UCSRxC UCSR0C
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#define UCSZx1 UCSZ01
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#define UCSZx0 UCSZ00
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#define UCSRxB UCSR0B
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#define RXENx RXEN0
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#define TXENx TXEN0
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#define UDREx UDRE0
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#define RXCx RXC0
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#define UDRx UDR0
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#define UDRIEx UDRIE0
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#define USARTx_RX_vect USART_RX_vect
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#define USARTx_UDRE_vect USART_UDRE_vect
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#elif defined (UBRR1H)
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#warning Using UART1
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#define UBRRxH UBRR1H
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#define UBRRxL UBRR1L
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#define UCSRxA UCSR1A
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#define U2Xx U2X1
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#define UCSRxC UCSR1C
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#define UCSZx1 UCSZ11
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#define UCSZx0 UCSZ10
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#define UCSRxB UCSR1B
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#define RXENx RXEN1
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#define TXENx TXEN1
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#define UDREx UDRE1
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#define RXCx RXC1
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#define UDRx UDR1
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#define UDRIEx UDRIE1
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#define USARTx_RX_vect USART1_RX_vect
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#define USARTx_UDRE_vect USART1_UDRE_vect
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#else
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#error No UART?
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#endif
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struct tx_ring {
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int buffer[UART_TX_BUFFER_SIZE];
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int start;
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int end;
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};
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struct rx_ring {
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int buffer[UART_RX_BUFFER_SIZE];
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int start;
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int end;
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};
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static struct tx_ring tx_buffer;
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static struct rx_ring rx_buffer;
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/* http://www.cs.mun.ca/~rod/Winter2007/4723/notes/serial/serial.html */
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void uart_init(void) {
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tx_buffer.start = 0;
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tx_buffer.end = 0;
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rx_buffer.start = 0;
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rx_buffer.end = 0;
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UBRRxH = UBRRH_VALUE;
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UBRRxL = UBRRL_VALUE;
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UCSRxC = _BV(UCSZx1) | _BV(UCSZx0); /* 8-bit data */
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UCSRxB = _BV(RXENx) | _BV(TXENx); /* Enable RX and TX */
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sei();
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}
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int uart_putchar(char c, FILE *stream) {
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if (c == '\n') {
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uart_putchar('\r', stream);
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}
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int write_pointer = (tx_buffer.end + 1) % UART_TX_BUFFER_SIZE;
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if (write_pointer != tx_buffer.start){
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tx_buffer.buffer[tx_buffer.end] = c;
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tx_buffer.end = write_pointer;
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/* Data available. Enable the transmit interrupt for serial port 0. */
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UCSRxB |= _BV(UDRIEx);
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}
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return 0;
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}
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int uart_getchar(FILE *stream) {
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int read_pointer = (rx_buffer.start + 1) % UART_RX_BUFFER_SIZE;
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rx_buffer.start = read_pointer;
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return rx_buffer.buffer[read_pointer];
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}
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ISR(USARTx_RX_vect) {
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int write_pointer = (rx_buffer.end + 1) % UART_RX_BUFFER_SIZE;
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/* Add next byte to ringbuffer if it has space available. */
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if (write_pointer != rx_buffer.start){
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rx_buffer.buffer[rx_buffer.end] = UDRx;
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rx_buffer.end = write_pointer;
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}
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}
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ISR(USARTx_UDRE_vect){
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int read_pointer = (tx_buffer.start + 1) % UART_TX_BUFFER_SIZE;
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/* Transmit next byte if data available in ringbuffer. */
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if (read_pointer != tx_buffer.end) {
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UDRx = tx_buffer.buffer[read_pointer];
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tx_buffer.start = read_pointer;
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} else {
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/* Nothing to send. Disable the transmit interrupt for serial port x. */
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UCSRxB &= ~_BV(UDRIEx);
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}
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}
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