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140 lines
4.1 KiB
140 lines
4.1 KiB
/*
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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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Modified 29 January 2009, Marius Kintel for Sanguino - http://www.sanguino.cc/
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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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#define RX_BUFFER_MASK 0x7f
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#if defined(__AVR_ATmega644P__)
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unsigned char rx_buffer[2][RX_BUFFER_SIZE];
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int rx_buffer_head[2] = {0, 0};
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int rx_buffer_tail[2] = {0, 0};
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#else
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unsigned char rx_buffer[1][RX_BUFFER_SIZE];
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int rx_buffer_head[1] = {0};
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int rx_buffer_tail[1] = {0};
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#endif
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#define BEGIN_SERIAL(uart_, baud_) \
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{ \
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UBRR##uart_##H = ((F_CPU / 16 + baud / 2) / baud - 1) >> 8; \
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UBRR##uart_##L = ((F_CPU / 16 + baud / 2) / baud - 1); \
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\
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/* reset config for UART */ \
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UCSR##uart_##A = 0; \
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UCSR##uart_##B = 0; \
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UCSR##uart_##C = 0; \
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\
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/* enable rx and tx */ \
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sbi(UCSR##uart_##B, RXEN##uart_);\
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sbi(UCSR##uart_##B, TXEN##uart_);\
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\
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/* enable interrupt on complete reception of a byte */ \
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sbi(UCSR##uart_##B, RXCIE##uart_); \
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UCSR##uart_##C = _BV(UCSZ##uart_##1)|_BV(UCSZ##uart_##0); \
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/* defaults to 8-bit, no parity, 1 stop bit */ \
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}
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void beginSerial(uint8_t uart, long baud)
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{
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if (uart == 0) BEGIN_SERIAL(0, baud)
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#if defined(__AVR_ATmega644P__)
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else BEGIN_SERIAL(1, baud)
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#endif
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}
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#define SERIAL_WRITE(uart_, c_) \
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while (!(UCSR##uart_##A & (1 << UDRE##uart_))) \
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; \
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UDR##uart_ = c
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void serialWrite(uint8_t uart, unsigned char c)
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{
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if (uart == 0) {
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SERIAL_WRITE(0, c);
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}
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#if defined(__AVR_ATmega644P__)
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else {
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SERIAL_WRITE(1, c);
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}
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#endif
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}
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int serialAvailable(uint8_t uart)
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{
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return (RX_BUFFER_SIZE + rx_buffer_head[uart] - rx_buffer_tail[uart]) & RX_BUFFER_MASK;
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}
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int serialRead(uint8_t uart)
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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[uart] == rx_buffer_tail[uart]) {
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return -1;
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} else {
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unsigned char c = rx_buffer[uart][rx_buffer_tail[uart]];
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rx_buffer_tail[uart] = (rx_buffer_tail[uart] + 1) & RX_BUFFER_MASK;
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return c;
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}
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}
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void serialFlush(uint8_t uart)
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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[uart] = rx_buffer_tail[uart];
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}
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#define UART_ISR(uart_) \
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ISR(USART##uart_##_RX_vect) \
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{ \
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unsigned char c = UDR##uart_; \
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\
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int i = (rx_buffer_head[uart_] + 1) & RX_BUFFER_MASK; \
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\
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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[uart_]) { \
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rx_buffer[uart_][rx_buffer_head[uart_]] = c; \
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rx_buffer_head[uart_] = i; \
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} \
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}
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UART_ISR(0)
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#if defined(__AVR_ATmega644P__)
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UART_ISR(1)
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#endif
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