240 lines
6.4 KiB
C++
240 lines
6.4 KiB
C++
/*
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HardwareSerial.cpp - Hardware serial library for Wiring
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Copyright (c) 2006 Nicholas Zambetti. All right reserved.
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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 Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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Modified 23 November 2006 by David A. Mellis
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*/
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#include <stdio.h>
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#include <string.h>
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#include <inttypes.h>
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#include "wiring.h"
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#include "wiring_private.h"
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#include "HardwareSerial.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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struct ring_buffer {
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unsigned char buffer[RX_BUFFER_SIZE];
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int head;
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int tail;
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};
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ring_buffer rx_buffer = { { 0 }, 0, 0 };
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#ifdef UDR1
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ring_buffer rx_buffer1 = { { 0 }, 0, 0 };
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#endif
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#ifdef UDR2
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ring_buffer rx_buffer2 = { { 0 }, 0, 0 };
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#endif
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#ifdef UDR3
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ring_buffer rx_buffer3 = { { 0 }, 0, 0 };
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#endif
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inline void store_char(unsigned char c, ring_buffer *rx_buffer)
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{
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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->buffer[rx_buffer->head] = c;
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rx_buffer->head = i;
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}
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}
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ISR(USART0_RX_vect)
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{
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unsigned char c = UDR0;
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store_char(c, &rx_buffer);
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}
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#ifdef UDR1
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ISR(USART1_RX_vect)
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{
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unsigned char c = UDR1;
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store_char(c, &rx_buffer1);
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}
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#ifdef UDR2
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ISR(USART2_RX_vect)
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{
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unsigned char c = UDR2;
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store_char(c, &rx_buffer2);
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}
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#ifdef UDR2
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ISR(USART3_RX_vect)
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{
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unsigned char c = UDR3;
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store_char(c, &rx_buffer3);
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}
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#endif
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#endif
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#else
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#if defined(__AVR_ATmega8__)
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SIGNAL(SIG_UART_RECV)
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#else
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SIGNAL(USART_RX_vect)
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#endif
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{
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#if defined(__AVR_ATmega8__)
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unsigned char c = UDR;
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#else
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unsigned char c = UDR0;
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#endif
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store_char(c, &rx_buffer);
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}
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#endif
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// Constructors ////////////////////////////////////////////////////////////////
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HardwareSerial::HardwareSerial(ring_buffer *rx_buffer,
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volatile uint8_t *ubrrh, volatile uint8_t *ubrrl,
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volatile uint8_t *ucsra, volatile uint8_t *ucsrb,
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volatile uint8_t *udr,
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uint8_t rxen, uint8_t txen, uint8_t rxcie, uint8_t udre, uint8_t u2x)
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{
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_rx_buffer = rx_buffer;
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_ubrrh = ubrrh;
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_ubrrl = ubrrl;
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_ucsra = ucsra;
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_ucsrb = ucsrb;
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_udr = udr;
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_rxen = rxen;
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_txen = txen;
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_rxcie = rxcie;
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_udre = udre;
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_u2x = u2x;
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}
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// Public Methods //////////////////////////////////////////////////////////////
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void HardwareSerial::begin(long baud)
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{
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uint16_t baud_setting;
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bool use_u2x;
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// U2X mode is needed for baud rates higher than (CPU Hz / 16)
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if (baud > F_CPU / 16) {
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use_u2x = true;
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} else {
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// figure out if U2X mode would allow for a better connection
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// calculate the percent difference between the baud-rate specified and
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// the real baud rate for both U2X and non-U2X mode (0-255 error percent)
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uint8_t nonu2x_baud_error = abs((int)(255-((F_CPU/(16*(((F_CPU/8/baud-1)/2)+1))*255)/baud)));
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uint8_t u2x_baud_error = abs((int)(255-((F_CPU/(8*(((F_CPU/4/baud-1)/2)+1))*255)/baud)));
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// prefer non-U2X mode because it handles clock skew better
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use_u2x = (nonu2x_baud_error > u2x_baud_error);
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}
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if (use_u2x) {
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*_ucsra = 1 << _u2x;
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baud_setting = (F_CPU / 4 / baud - 1) / 2;
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} else {
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*_ucsra = 0;
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baud_setting = (F_CPU / 8 / baud - 1) / 2;
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}
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// assign the baud_setting, a.k.a. ubbr (USART Baud Rate Register)
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*_ubrrh = baud_setting >> 8;
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*_ubrrl = baud_setting;
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sbi(*_ucsrb, _rxen);
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sbi(*_ucsrb, _txen);
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sbi(*_ucsrb, _rxcie);
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}
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void HardwareSerial::end()
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{
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cbi(*_ucsrb, _rxen);
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cbi(*_ucsrb, _txen);
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cbi(*_ucsrb, _rxcie);
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}
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uint8_t HardwareSerial::available(void)
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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 HardwareSerial::read(void)
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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->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 HardwareSerial::flush()
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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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// 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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void HardwareSerial::write(uint8_t c)
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{
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while (!((*_ucsra) & (1 << _udre)))
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;
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*_udr = c;
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}
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// Preinstantiate Objects //////////////////////////////////////////////////////
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#if defined(__AVR_ATmega8__)
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HardwareSerial Serial(&rx_buffer, &UBRRH, &UBRRL, &UCSRA, &UCSRB, &UDR, RXEN, TXEN, RXCIE, UDRE, U2X);
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#else
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HardwareSerial Serial(&rx_buffer, &UBRR0H, &UBRR0L, &UCSR0A, &UCSR0B, &UDR0, RXEN0, TXEN0, RXCIE0, UDRE0, U2X0);
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#endif
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#ifdef UDR1
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HardwareSerial Serial1(&rx_buffer1, &UBRR1H, &UBRR1L, &UCSR1A, &UCSR1B, &UDR1, RXEN1, TXEN1, RXCIE1, UDRE1, U2X1);
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#endif
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#ifdef UDR2
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HardwareSerial Serial2(&rx_buffer2, &UBRR2H, &UBRR2L, &UCSR2A, &UCSR2B, &UDR2, RXEN2, TXEN2, RXCIE2, UDRE2, U2X2);
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#endif
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#ifdef UDR3
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HardwareSerial Serial3(&rx_buffer3, &UBRR3H, &UBRR3L, &UCSR3A, &UCSR3B, &UDR3, RXEN3, TXEN3, RXCIE3, UDRE3, U2X3);
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#endif
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