环形队列
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转自：http://wiki.geek-workshop.com/doku.php?id=arduino:cores:hardwareserial.cpp/* HardwareSerial.cpp - Hardware serial library for Wiring Copyright (c) 2006 Nicholas Zambetti. All right reserved. This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Modified 23 November 2006 by David A. Mellis Modified 28 September 2010 by Mark Sproul Modified 14 August 2012 by Alarus*/ #include <stdlib.h>#include <stdio.h>#include <string.h>#include <inttypes.h>#include "Arduino.h"#include "wiring_private.h" // 这下一行禁用了整个HardwareSerial.cpp，// 这样的话我可以支持Attiny系列和任何其他没有UART的芯片#if defined(UBRRH) || defined(UBRR0H) || defined(UBRR1H) || defined(UBRR2H) || defined(UBRR3H) #include "HardwareSerial.h" // 定义常量和变量用于缓冲输入的串行数据。我们使用一个环形缓冲区（我认为），// 其中头指针是下一个输入字符要写入的位置的索引，// 尾指针是要读的字符的位置的索引。#if (RAMEND < 1000) #define SERIAL_BUFFER_SIZE 16#else #define SERIAL_BUFFER_SIZE 64#endif struct ring_buffer{ unsigned char buffer[SERIAL_BUFFER_SIZE]; volatile unsigned int head; volatile unsigned int tail;}; #if defined(USBCON) ring_buffer rx_buffer = { { 0 }, 0, 0}; ring_buffer tx_buffer = { { 0 }, 0, 0};#endif#if defined(UBRRH) || defined(UBRR0H) ring_buffer rx_buffer = { { 0 }, 0, 0 }; ring_buffer tx_buffer = { { 0 }, 0, 0 };#endif#if defined(UBRR1H) ring_buffer rx_buffer1 = { { 0 }, 0, 0 }; ring_buffer tx_buffer1 = { { 0 }, 0, 0 };#endif#if defined(UBRR2H) ring_buffer rx_buffer2 = { { 0 }, 0, 0 }; ring_buffer tx_buffer2 = { { 0 }, 0, 0 };#endif#if defined(UBRR3H) ring_buffer rx_buffer3 = { { 0 }, 0, 0 }; ring_buffer tx_buffer3 = { { 0 }, 0, 0 };#endif inline void store_char(unsigned char c, ring_buffer *buffer){ int i = (unsigned int)(buffer->head + 1) % SERIAL_BUFFER_SIZE; // 如果我们要把收到的字符存储在这个位置，正好在尾部之前 // (意思是头部会推进到尾部的当前位置）， // 将会使缓冲区溢出，所以我们不写这个字符或推进头部。 if (i != buffer->tail) { buffer->buffer[buffer->head] = c; buffer->head = i; }} #if !defined(USART0_RX_vect) && defined(USART1_RX_vect)// 什么都不做 - 在32u4上第一个USART是USART1#else#if !defined(USART_RX_vect) && !defined(SIG_USART0_RECV) && \ !defined(SIG_UART0_RECV) && !defined(USART0_RX_vect) && \!defined(SIG_UART_RECV) #error "Don't know what the Data Received vector is called for the first UART"#else void serialEvent() __attribute__((weak)); void serialEvent() {} #define serialEvent_implemented#if defined(USART_RX_vect) SIGNAL(USART_RX_vect)#elif defined(SIG_USART0_RECV) SIGNAL(SIG_USART0_RECV)#elif defined(SIG_UART0_RECV) SIGNAL(SIG_UART0_RECV)#elif defined(USART0_RX_vect) SIGNAL(USART0_RX_vect)#elif defined(SIG_UART_RECV) SIGNAL(SIG_UART_RECV)#endif { #if defined(UDR0) if (bit_is_clear(UCSR0A, UPE0)) { unsigned char c = UDR0; store_char(c, &rx_buffer); } else { unsigned char c = UDR0; }; #elif defined(UDR) if (bit_is_clear(UCSRA, PE)) { unsigned char c = UDR; store_char(c, &rx_buffer); } else { unsigned char c = UDR; }; #else #error UDR not defined #endif }#endif#endif #if defined(USART1_RX_vect) void serialEvent1() __attribute__((weak)); void serialEvent1() {} #define serialEvent1_implemented SIGNAL(USART1_RX_vect) { if (bit_is_clear(UCSR1A, UPE1)) { unsigned char c = UDR1; store_char(c, &rx_buffer1); } else { unsigned char c = UDR1; }; }#elif defined(SIG_USART1_RECV) #error SIG_USART1_RECV#endif #if defined(USART2_RX_vect) && defined(UDR2) void serialEvent2() __attribute__((weak)); void serialEvent2() {} #define serialEvent2_implemented SIGNAL(USART2_RX_vect) { if (bit_is_clear(UCSR2A, UPE2)) { unsigned char c = UDR2; store_char(c, &rx_buffer2); } else { unsigned char c = UDR2; }; }#elif defined(SIG_USART2_RECV) #error SIG_USART2_RECV#endif #if defined(USART3_RX_vect) && defined(UDR3) void serialEvent3() __attribute__((weak)); void serialEvent3() {} #define serialEvent3_implemented SIGNAL(USART3_RX_vect) { if (bit_is_clear(UCSR3A, UPE3)) { unsigned char c = UDR3; store_char(c, &rx_buffer3); } else { unsigned char c = UDR3; }; }#elif defined(SIG_USART3_RECV) #error SIG_USART3_RECV#endif void serialEventRun(void){#ifdef serialEvent_implemented if (Serial.available()) serialEvent();#endif#ifdef serialEvent1_implemented if (Serial1.available()) serialEvent1();#endif#ifdef serialEvent2_implemented if (Serial2.available()) serialEvent2();#endif#ifdef serialEvent3_implemented if (Serial3.available()) serialEvent3();#endif} #if !defined(USART0_UDRE_vect) && defined(USART1_UDRE_vect)// 什么都不做 - 在32u4上第一个USART是USART1#else#if !defined(UART0_UDRE_vect) && !defined(UART_UDRE_vect) && !defined(USART0_UDRE_vect) && !defined(USART_UDRE_vect) #error "Don't know what the Data Register Empty vector is called for the first UART"#else#if defined(UART0_UDRE_vect)ISR(UART0_UDRE_vect)#elif defined(UART_UDRE_vect)ISR(UART_UDRE_vect)#elif defined(USART0_UDRE_vect)ISR(USART0_UDRE_vect)#elif defined(USART_UDRE_vect)ISR(USART_UDRE_vect)#endif{ if (tx_buffer.head == tx_buffer.tail) {// 缓冲区空，所以禁止中断#if defined(UCSR0B) cbi(UCSR0B, UDRIE0);#else cbi(UCSRB, UDRIE);#endif } else { // 在输出缓冲区还有数据，发送下个字节。 unsigned char c = tx_buffer.buffer[tx_buffer.tail]; tx_buffer.tail = (tx_buffer.tail + 1) % SERIAL_BUFFER_SIZE; #if defined(UDR0) UDR0 = c; #elif defined(UDR) UDR = c; #else #error UDR not defined #endif }}#endif#endif #ifdef USART1_UDRE_vectISR(USART1_UDRE_vect){ if (tx_buffer1.head == tx_buffer1.tail) {// 缓冲区空，所以禁用中断。 cbi(UCSR1B, UDRIE1); } else { // 在输出缓冲区还有数据，发送下个字节。 unsigned char c = tx_buffer1.buffer[tx_buffer1.tail]; tx_buffer1.tail = (tx_buffer1.tail + 1) % SERIAL_BUFFER_SIZE; UDR1 = c; }}#endif #ifdef USART2_UDRE_vectISR(USART2_UDRE_vect){ if (tx_buffer2.head == tx_buffer2.tail) {// 缓冲区空，所以禁用中断。 cbi(UCSR2B, UDRIE2); } else { // 在输出缓冲区还有数据，发送下个字节。 unsigned char c = tx_buffer2.buffer[tx_buffer2.tail]; tx_buffer2.tail = (tx_buffer2.tail + 1) % SERIAL_BUFFER_SIZE; UDR2 = c; }}#endif #ifdef USART3_UDRE_vectISR(USART3_UDRE_vect){ if (tx_buffer3.head == tx_buffer3.tail) {// 缓冲区空，所以禁用中断。 cbi(UCSR3B, UDRIE3); } else { // 在输出缓冲区还有数据，发送下个字节。 unsigned char c = tx_buffer3.buffer[tx_buffer3.tail]; tx_buffer3.tail = (tx_buffer3.tail + 1) % SERIAL_BUFFER_SIZE; UDR3 = c; }}#endif // 构造函数 //////////////////////////////////////////////////////////////// HardwareSerial::HardwareSerial(ring_buffer *rx_buffer, ring_buffer *tx_buffer, volatile uint8_t *ubrrh, volatile uint8_t *ubrrl, volatile uint8_t *ucsra, volatile uint8_t *ucsrb, volatile uint8_t *ucsrc, volatile uint8_t *udr, uint8_t rxen, uint8_t txen, uint8_t rxcie, uint8_t udrie, uint8_t u2x){ _rx_buffer = rx_buffer; _tx_buffer = tx_buffer; _ubrrh = ubrrh; _ubrrl = ubrrl; _ucsra = ucsra; _ucsrb = ucsrb; _ucsrc = ucsrc; _udr = udr; _rxen = rxen; _txen = txen; _rxcie = rxcie; _udrie = udrie; _u2x = u2x;} // 公用方法 ////////////////////////////////////////////////////////////// void HardwareSerial::begin(unsigned long baud){ uint16_t baud_setting; bool use_u2x = true; #if F_CPU == 16000000UL // 为了兼容性所作的硬编码例外，包括Duemilanove及更早的板子上板载的bootloader， // 以及Uno和Mega 2560上8u2的固件。 if (baud == 57600) { use_u2x = false; }#endif try_again: if (use_u2x) { *_ucsra = 1 << _u2x; baud_setting = (F_CPU / 4 / baud - 1) / 2; } else { *_ucsra = 0; baud_setting = (F_CPU / 8 / baud - 1) / 2; } if ((baud_setting > 4095) && use_u2x) { use_u2x = false; goto try_again; } // 分配baud_setting,又名ubrr (USART Baud Rate Register，USART波特率寄存器) *_ubrrh = baud_setting >> 8; *_ubrrl = baud_setting; transmitting = false; sbi(*_ucsrb, _rxen); sbi(*_ucsrb, _txen); sbi(*_ucsrb, _rxcie); cbi(*_ucsrb, _udrie);} void HardwareSerial::begin(unsigned long baud, byte config){ uint16_t baud_setting; uint8_t current_config; bool use_u2x = true; #if F_CPU == 16000000UL // 为了兼容性所作的硬编码例外，包括Duemilanove及更早的板子上板载的bootloader， // 以及Uno和Mega 2560上8u2的固件。 if (baud == 57600) { use_u2x = false; }#endif try_again: if (use_u2x) { *_ucsra = 1 << _u2x; baud_setting = (F_CPU / 4 / baud - 1) / 2; } else { *_ucsra = 0; baud_setting = (F_CPU / 8 / baud - 1) / 2; } if ((baud_setting > 4095) && use_u2x) { use_u2x = false; goto try_again; } // 分配baud_setting,又名ubrr (USART Baud Rate Register，USART波特率寄存器) *_ubrrh = baud_setting >> 8; *_ubrrl = baud_setting; //设置数据位，奇偶校验位和停止位#if defined(__AVR_ATmega8__) config |= 0x80; // select UCSRC register (shared with UBRRH)#endif *_ucsrc = config; sbi(*_ucsrb, _rxen); sbi(*_ucsrb, _txen); sbi(*_ucsrb, _rxcie); cbi(*_ucsrb, _udrie);} void HardwareSerial::end(){ // 等待发出数据的传输 while (_tx_buffer->head != _tx_buffer->tail) ; cbi(*_ucsrb, _rxen); cbi(*_ucsrb, _txen); cbi(*_ucsrb, _rxcie); cbi(*_ucsrb, _udrie); // 清空任何接收到的数据 _rx_buffer->head = _rx_buffer->tail;} int HardwareSerial::available(void){ return (unsigned int)(SERIAL_BUFFER_SIZE + _rx_buffer->head - _rx_buffer->tail) % SERIAL_BUFFER_SIZE;} int HardwareSerial::peek(void){ if (_rx_buffer->head == _rx_buffer->tail) { return -1; } else { return _rx_buffer->buffer[_rx_buffer->tail]; }} int HardwareSerial::read(void){ // 如果头指针不在尾指针之前，我们没有收到任何字符 if (_rx_buffer->head == _rx_buffer->tail) { return -1; } else { unsigned char c = _rx_buffer->buffer[_rx_buffer->tail]; _rx_buffer->tail = (unsigned int)(_rx_buffer->tail + 1) % SERIAL_BUFFER_SIZE; return c; }} void HardwareSerial::flush(){ // 当缓冲区不为空时，UDR保持完整，所以当EMPTY && SENT时，TXC触发。 while (transmitting && ! (*_ucsra & _BV(TXC0))); transmitting = false;} size_t HardwareSerial::write(uint8_t c){ int i = (_tx_buffer->head + 1) % SERIAL_BUFFER_SIZE; // 如果输出缓冲区满了，它没有什么可做， // 除了等待中断处理程序清空它。 // ???: 这里以return 0代替? while (i == _tx_buffer->tail) ; _tx_buffer->buffer[_tx_buffer->head] = c; _tx_buffer->head = i; sbi(*_ucsrb, _udrie); // 清空TXC位 -- "不能通过在位址上写入1来清空" transmitting = true; sbi(*_ucsra, TXC0); return 1;} HardwareSerial::operator bool() {return true;} // Preinstantiate对象 ////////////////////////////////////////////////////// #if defined(UBRRH) && defined(UBRRL) HardwareSerial Serial(&rx_buffer, &tx_buffer, &UBRRH, &UBRRL, &UCSRA, &UCSRB, &UCSRC, &UDR, RXEN, TXEN, RXCIE, UDRIE, U2X);#elif defined(UBRR0H) && defined(UBRR0L) HardwareSerial Serial(&rx_buffer, &tx_buffer, &UBRR0H, &UBRR0L, &UCSR0A, &UCSR0B, &UCSR0C, &UDR0, RXEN0, TXEN0, RXCIE0, UDRIE0, U2X0);#elif defined(USBCON) // 什么都不做 - 在CDC代码初始化串行对象和缓冲区#else #error no serial port defined (port 0)#endif #if defined(UBRR1H) HardwareSerial Serial1(&rx_buffer1, &tx_buffer1, &UBRR1H, &UBRR1L, &UCSR1A, &UCSR1B, &UCSR1C, &UDR1, RXEN1, TXEN1, RXCIE1, UDRIE1, U2X1);#endif#if defined(UBRR2H) HardwareSerial Serial2(&rx_buffer2, &tx_buffer2, &UBRR2H, &UBRR2L, &UCSR2A, &UCSR2B, &UCSR2C, &UDR2, RXEN2, TXEN2, RXCIE2, UDRIE2, U2X2);#endif#if defined(UBRR3H) HardwareSerial Serial3(&rx_buffer3, &tx_buffer3, &UBRR3H, &UBRR3L, &UCSR3A, &UCSR3B, &UCSR3C, &UDR3, RXEN3, TXEN3, RXCIE3, UDRIE3, U2X3);#endif #endif // 全部文件
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