1 | /*
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2 | SoftwareSerial.cpp - library for Arduino M0/M0 pro
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3 | Copyright (c) 2016 Arduino Srl. All rights reserved.
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4 | Written by Chiara Ruggeri (chiara@arduino.org)
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5 |
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6 | This library is free software; you can redistribute it and/or
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7 | modify it under the terms of the GNU Lesser General Public
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8 | License as published by the Free Software Foundation; either
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9 | version 2.1 of the License, or (at your option) any later version.
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10 |
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11 | This library is distributed in the hope that it will be useful,
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12 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 | Lesser General Public License for more details.
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15 |
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16 | You should have received a copy of the GNU Lesser General Public
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17 | License along with this library; if not, write to the Free Software
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18 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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19 |
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20 | Enjoy!
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21 | */
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22 |
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23 |
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24 | #include <Arduino.h>
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25 | #include <SoftwareSerial.h>
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26 | #include <variant.h>
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27 | #include <WInterrupts.h>
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28 |
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29 | SoftwareSerial *SoftwareSerial::active_object = 0;
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30 | char SoftwareSerial::_receive_buffer[_SS_MAX_RX_BUFF];
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31 | volatile uint8_t SoftwareSerial::_receive_buffer_tail = 0;
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32 | volatile uint8_t SoftwareSerial::_receive_buffer_head = 0;
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33 |
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34 |
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35 | bool SoftwareSerial::listen()
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36 | {
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37 | if (!_rx_delay_stopbit)
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38 | return false;
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39 |
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40 | if (active_object != this)
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41 | {
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42 | if (active_object)
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43 | active_object->stopListening();
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44 |
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45 | _buffer_overflow = false;
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46 | _receive_buffer_head = _receive_buffer_tail = 0;
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47 | active_object = this;
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48 |
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49 | if(_inverse_logic)
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50 | //Start bit high
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51 | attachInterrupt(_receivePin, handle_interrupt, RISING);
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52 | else
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53 | //Start bit low
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54 | attachInterrupt(_receivePin, handle_interrupt, FALLING);
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55 |
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56 |
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57 | return true;
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58 | }
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59 | return false;
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60 | }
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61 |
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62 | bool SoftwareSerial::stopListening()
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63 | {
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64 | if (active_object == this)
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65 | {
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66 | EIC->INTENCLR.reg = EIC_INTENCLR_EXTINT( 1 << digitalPinToInterrupt( _receivePin )) ;
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67 | active_object = NULL;
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68 | return true;
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69 | }
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70 | return false;
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71 | }
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72 |
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73 |
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74 | void SoftwareSerial::recv()
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75 | {
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76 |
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77 | uint8_t d = 0;
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78 |
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79 | // If RX line is high, then we don't see any start bit
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80 | // so interrupt is probably not for us
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81 | if (_inverse_logic ? rx_pin_read() : !rx_pin_read())
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82 | {
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83 |
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84 | EIC->INTENCLR.reg = EIC_INTENCLR_EXTINT( 1 << digitalPinToInterrupt(_receivePin));
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85 |
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86 | // Wait approximately 1/2 of a bit width to "center" the sample
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87 | delayMicroseconds(_rx_delay_centering);
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88 |
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89 | // Read each of the 8 bits
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90 | for (uint8_t i=8; i > 0; --i)
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91 | {
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92 |
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93 | delayMicroseconds(_rx_delay_intrabit);
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94 | d >>= 1;
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95 | if (rx_pin_read()){
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96 | d |= 0x80;
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97 | }
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98 |
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99 | }
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100 | if (_inverse_logic){
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101 | d = ~d;
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102 | }
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103 |
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104 | // if buffer full, set the overflow flag and return
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105 | uint8_t next = (_receive_buffer_tail + 1) % _SS_MAX_RX_BUFF;
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106 | if (next != _receive_buffer_head)
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107 | {
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108 | // save new data in buffer: tail points to where byte goes
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109 | _receive_buffer[_receive_buffer_tail] = d; // save new byte
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110 | _receive_buffer_tail = next;
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111 | }
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112 | else
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113 | {
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114 | _buffer_overflow = true;
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115 | }
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116 |
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117 | // skip the stop bit
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118 | delayMicroseconds(_rx_delay_stopbit);
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119 |
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120 | EIC->INTENSET.reg = EIC_INTENSET_EXTINT( 1 << digitalPinToInterrupt(_receivePin));
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121 | }
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122 | }
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123 |
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124 |
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125 | uint32_t SoftwareSerial::rx_pin_read()
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126 | {
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127 | return _receivePortRegister->reg & digitalPinToBitMask(_receivePin);
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128 | }
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129 |
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130 | /* static */
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131 | inline void SoftwareSerial::handle_interrupt()
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132 | {
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133 | if (active_object)
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134 | {
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135 | active_object->recv();
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136 | }
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137 | }
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138 |
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139 |
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140 | // Constructor
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141 | SoftwareSerial::SoftwareSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic /* = false */) :
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142 | _rx_delay_centering(0),
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143 | _rx_delay_intrabit(0),
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144 | _rx_delay_stopbit(0),
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145 | _tx_delay(0),
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146 | _buffer_overflow(false),
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147 | _inverse_logic(inverse_logic)
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148 | {
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149 | _receivePin = receivePin;
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150 | _transmitPin = transmitPin;
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151 | }
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152 |
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153 | // Destructor
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154 | SoftwareSerial::~SoftwareSerial()
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155 | {
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156 | end();
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157 | }
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158 |
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159 | void SoftwareSerial::setTX(uint8_t tx)
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160 | {
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161 | // First write, then set output. If we do this the other way around,
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162 | // the pin would be output low for a short while before switching to
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163 | // output hihg. Now, it is input with pullup for a short while, which
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164 | // is fine. With inverse logic, either order is fine.
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165 | digitalWrite(tx, _inverse_logic ? LOW : HIGH);
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166 | pinMode(tx, OUTPUT);
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167 | _transmitBitMask = digitalPinToBitMask(tx);
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168 | PortGroup * port = digitalPinToPort(tx);
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169 | _transmitPortRegister = portOutputRegister(port);
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170 |
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171 | }
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172 |
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173 | void SoftwareSerial::setRX(uint8_t rx)
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174 | {
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175 | pinMode(rx, INPUT);
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176 | if (!_inverse_logic)
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177 | digitalWrite(rx, HIGH); // pullup for normal logic!
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178 | _receivePin = rx;
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179 | _receiveBitMask = digitalPinToBitMask(rx);
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180 | PortGroup * port = digitalPinToPort(rx);
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181 | _receivePortRegister = portInputRegister(port);
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182 |
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183 | }
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184 |
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185 |
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186 | void SoftwareSerial::begin(long speed)
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187 | {
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188 | setTX(_transmitPin);
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189 | setRX(_receivePin);
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190 | // Precalculate the various delays
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191 | //Calculate the distance between bit in micro seconds
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192 | uint32_t bit_delay = (float(1)/speed)*1000000;
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193 |
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194 | _tx_delay = bit_delay;
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195 |
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196 | // Only setup rx when we have a valid PCINT for this pin
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197 | if (digitalPinToInterrupt(_receivePin)!=NOT_AN_INTERRUPT) {
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198 | //Wait 1/2 bit - 2 micro seconds (time for interrupt to be served)
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199 | _rx_delay_centering = (bit_delay/2) - 2;
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200 | //Wait 1 bit - 2 micro seconds (time in each loop iteration)
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201 | _rx_delay_intrabit = bit_delay - 2;
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202 | //Wait 1 bit (the stop one)
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203 | _rx_delay_stopbit = bit_delay;
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204 |
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205 |
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206 | delayMicroseconds(_tx_delay);
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207 | }
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208 | listen();
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209 | }
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210 |
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211 | void SoftwareSerial::end()
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212 | {
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213 | stopListening();
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214 | }
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215 |
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216 | int SoftwareSerial::read()
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217 | {
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218 | if (!isListening()){
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219 | return -1;}
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220 |
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221 |
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222 | // Empty buffer?
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223 | if (_receive_buffer_head == _receive_buffer_tail){
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224 | return -1;}
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225 |
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226 | // Read from "head"
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227 | uint8_t d = _receive_buffer[_receive_buffer_head]; // grab next byte
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228 | _receive_buffer_head = (_receive_buffer_head + 1) % _SS_MAX_RX_BUFF;
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229 | return d;
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230 | }
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231 |
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232 |
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233 | int SoftwareSerial::available()
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234 | {
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235 | if (!isListening())
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236 | return 0;
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237 |
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238 | return (_receive_buffer_tail + _SS_MAX_RX_BUFF - _receive_buffer_head) % _SS_MAX_RX_BUFF;
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239 | }
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240 |
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241 |
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242 | size_t SoftwareSerial::write(uint8_t b)
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243 | {
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244 | if (_tx_delay == 0) {
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245 | setWriteError();
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246 | return 0;
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247 | }
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248 |
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249 | // By declaring these as local variables, the compiler will put them
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250 | // in registers _before_ disabling interrupts and entering the
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251 | // critical timing sections below, which makes it a lot easier to
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252 | // verify the cycle timings
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253 | volatile PORT_OUT_Type *reg = _transmitPortRegister;
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254 | uint32_t reg_mask = _transmitBitMask;
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255 | uint32_t inv_mask = ~_transmitBitMask;
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256 | bool inv = _inverse_logic;
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257 | uint16_t delay = _tx_delay;
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258 |
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259 | if (inv)
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260 | b = ~b;
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261 | // turn off interrupts for a clean txmit
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262 | EIC->INTENCLR.reg = EIC_INTENCLR_EXTINT( 1 << digitalPinToInterrupt( _receivePin ));
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263 |
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264 | // Write the start bit
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265 | if (inv)
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266 | reg->reg |= reg_mask;
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267 | else
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268 | reg->reg &= inv_mask;
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269 |
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270 | delayMicroseconds(delay);
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271 |
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272 |
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273 | // Write each of the 8 bits
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274 | for (uint8_t i = 8; i > 0; --i)
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275 | {
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276 | if (b & 1) // choose bit
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277 | reg->reg |= reg_mask; // send 1
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278 | else
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279 | reg->reg &= inv_mask; // send 0
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280 |
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281 | delayMicroseconds(delay);
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282 | b >>= 1;
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283 | }
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284 |
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285 | // restore pin to natural state
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286 | if (inv)
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287 | reg->reg &= inv_mask;
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288 | else
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289 | reg->reg |= reg_mask;
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290 |
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291 |
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292 | EIC->INTENSET.reg = EIC_INTENSET_EXTINT( 1 << digitalPinToInterrupt( _receivePin ) ) ;
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293 |
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294 | delayMicroseconds(delay);
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295 |
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296 | return 1;
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297 | }
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298 |
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299 | void SoftwareSerial::flush()
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300 | {
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301 | if (!isListening())
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302 | return;
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303 |
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304 | EIC->INTENCLR.reg = EIC_INTENCLR_EXTINT( 1 << digitalPinToInterrupt( _receivePin ) ) ;
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305 |
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306 | _receive_buffer_head = _receive_buffer_tail = 0;
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307 |
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308 | EIC->INTENSET.reg = EIC_INTENSET_EXTINT( 1 << digitalPinToInterrupt( _receivePin ) ) ;
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309 |
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310 | }
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311 |
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312 | int SoftwareSerial::peek()
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313 | {
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314 | if (!isListening())
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315 | return -1;
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316 |
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317 | // Empty buffer?
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318 | if (_receive_buffer_head == _receive_buffer_tail)
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319 | return -1;
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320 |
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321 | // Read from "head"
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322 | return _receive_buffer[_receive_buffer_head];
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323 | }
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