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129 lines
3.4 KiB
C
Executable File
129 lines
3.4 KiB
C
Executable File
/*
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wiring_serial.c - serial functions.
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Part of Arduino - http://www.arduino.cc/
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Copyright (c) 2005-2006 David A. Mellis
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General
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Public License along with this library; if not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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Boston, MA 02111-1307 USA
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$Id: wiring.c 248 2007-02-03 15:36:30Z mellis $
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*/
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#include "wiring_private.h"
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// Define constants and variables for buffering incoming serial data. We're
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// using a ring buffer (I think), in which rx_buffer_head is the index of the
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// location to which to write the next incoming character and rx_buffer_tail
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// is the index of the location from which to read.
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#define RX_BUFFER_SIZE 128
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unsigned char rx_buffer[RX_BUFFER_SIZE];
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int rx_buffer_head = 0;
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int rx_buffer_tail = 0;
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void beginSerial(long baud)
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{
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#if defined(__AVR_ATmega168__)
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UBRR0H = ((F_CPU / 16 + baud / 2) / baud - 1) >> 8;
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UBRR0L = ((F_CPU / 16 + baud / 2) / baud - 1);
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// enable rx and tx
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sbi(UCSR0B, RXEN0);
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sbi(UCSR0B, TXEN0);
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// enable interrupt on complete reception of a byte
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sbi(UCSR0B, RXCIE0);
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#else
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UBRRH = ((F_CPU / 16 + baud / 2) / baud - 1) >> 8;
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UBRRL = ((F_CPU / 16 + baud / 2) / baud - 1);
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// enable rx and tx
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sbi(UCSRB, RXEN);
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sbi(UCSRB, TXEN);
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// enable interrupt on complete reception of a byte
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sbi(UCSRB, RXCIE);
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#endif
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// defaults to 8-bit, no parity, 1 stop bit
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}
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void serialWrite(unsigned char c)
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{
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#if defined(__AVR_ATmega168__)
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while (!(UCSR0A & (1 << UDRE0)))
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;
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UDR0 = c;
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#else
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while (!(UCSRA & (1 << UDRE)))
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;
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UDR = c;
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#endif
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}
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int serialAvailable()
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{
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return (RX_BUFFER_SIZE + rx_buffer_head - rx_buffer_tail) % RX_BUFFER_SIZE;
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}
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int serialRead()
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{
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// if the head isn't ahead of the tail, we don't have any characters
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if (rx_buffer_head == rx_buffer_tail) {
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return -1;
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} else {
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unsigned char c = rx_buffer[rx_buffer_tail];
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rx_buffer_tail = (rx_buffer_tail + 1) % RX_BUFFER_SIZE;
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return c;
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}
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}
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void serialFlush()
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{
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// don't reverse this or there may be problems if the RX interrupt
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// occurs after reading the value of rx_buffer_head but before writing
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// the value to rx_buffer_tail; the previous value of rx_buffer_head
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// may be written to rx_buffer_tail, making it appear as if the buffer
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// were full, not empty.
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rx_buffer_head = rx_buffer_tail;
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}
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#if defined(__AVR_ATmega168__)
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SIGNAL(SIG_USART_RECV)
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#else
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SIGNAL(SIG_UART_RECV)
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#endif
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{
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#if defined(__AVR_ATmega168__)
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unsigned char c = UDR0;
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#else
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unsigned char c = UDR;
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#endif
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int i = (rx_buffer_head + 1) % RX_BUFFER_SIZE;
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// if we should be storing the received character into the location
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// just before the tail (meaning that the head would advance to the
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// current location of the tail), we're about to overflow the buffer
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// and so we don't write the character or advance the head.
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if (i != rx_buffer_tail) {
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rx_buffer[rx_buffer_head] = c;
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rx_buffer_head = i;
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}
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} |