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<li class="navelem"><a class="el" href="dir_bc0718b08fb2015b8e59c47b2805f60c.html">libraries</a></li><li class="navelem"><a class="el" href="dir_3dd03323535933fb3f714c41ff7a94da.html">RingOscillatorNoiseSource</a></li> </ul>
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<div class="title">RingOscillatorNoiseSource.cpp</div> </div>
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<div class="contents">
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<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">/*</span></div>
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<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment"> * Copyright (C) 2015 Southern Storm Software, Pty Ltd.</span></div>
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<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment"> *</span></div>
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<div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment"> * Permission is hereby granted, free of charge, to any person obtaining a</span></div>
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<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment"> * copy of this software and associated documentation files (the "Software"),</span></div>
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<div class="line"><a name="l00006"></a><span class="lineno"> 6</span> <span class="comment"> * to deal in the Software without restriction, including without limitation</span></div>
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<div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="comment"> * the rights to use, copy, modify, merge, publish, distribute, sublicense,</span></div>
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<div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="comment"> * and/or sell copies of the Software, and to permit persons to whom the</span></div>
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<div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="comment"> * Software is furnished to do so, subject to the following conditions:</span></div>
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<div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="comment"> *</span></div>
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<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="comment"> * The above copyright notice and this permission notice shall be included</span></div>
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<div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="comment"> * in all copies or substantial portions of the Software.</span></div>
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<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="comment"> *</span></div>
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<div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="comment"> * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS</span></div>
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<div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="comment"> * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,</span></div>
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<div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="comment"> * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE</span></div>
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<div class="line"><a name="l00017"></a><span class="lineno"> 17</span> <span class="comment"> * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER</span></div>
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<div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="comment"> * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING</span></div>
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<div class="line"><a name="l00019"></a><span class="lineno"> 19</span> <span class="comment"> * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER</span></div>
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<div class="line"><a name="l00020"></a><span class="lineno"> 20</span> <span class="comment"> * DEALINGS IN THE SOFTWARE.</span></div>
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<div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="comment"> */</span></div>
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<div class="line"><a name="l00022"></a><span class="lineno"> 22</span> </div>
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<div class="line"><a name="l00023"></a><span class="lineno"> 23</span> <span class="preprocessor">#include "RingOscillatorNoiseSource.h"</span></div>
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<div class="line"><a name="l00024"></a><span class="lineno"> 24</span> <span class="preprocessor">#include "Crypto.h"</span></div>
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<div class="line"><a name="l00025"></a><span class="lineno"> 25</span> <span class="preprocessor">#include "RNG.h"</span></div>
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<div class="line"><a name="l00026"></a><span class="lineno"> 26</span> <span class="preprocessor">#include <Arduino.h></span></div>
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<div class="line"><a name="l00027"></a><span class="lineno"> 27</span> </div>
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<div class="line"><a name="l00100"></a><span class="lineno"> 100</span> <span class="comment">// Choose the input capture timer and pin to use for this board.</span></div>
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<div class="line"><a name="l00101"></a><span class="lineno"> 101</span> <span class="preprocessor">#if defined(__AVR_ATmega2560__) || defined(__AVR_ATmega1280__)</span></div>
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<div class="line"><a name="l00102"></a><span class="lineno"> 102</span> <span class="preprocessor"></span><span class="comment">// Arduino Mega or Mega 2560 - input capture on TIMER4 and D49/PL0.</span></div>
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<div class="line"><a name="l00103"></a><span class="lineno"> 103</span> <span class="preprocessor">#define RING_TIMER 4</span></div>
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<div class="line"><a name="l00104"></a><span class="lineno"> 104</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_PIN 49</span></div>
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<div class="line"><a name="l00105"></a><span class="lineno"> 105</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_CAPT_vect TIMER4_CAPT_vect</span></div>
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<div class="line"><a name="l00106"></a><span class="lineno"> 106</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_ICR ICR4</span></div>
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<div class="line"><a name="l00107"></a><span class="lineno"> 107</span> <span class="preprocessor"></span><span class="preprocessor">#elif defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega16U4__)</span></div>
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<div class="line"><a name="l00108"></a><span class="lineno"> 108</span> <span class="preprocessor"></span><span class="comment">// Arduino Leonardo - input capture on Timer1 and D4/PD4.</span></div>
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<div class="line"><a name="l00109"></a><span class="lineno"> 109</span> <span class="preprocessor">#define RING_TIMER 1</span></div>
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<div class="line"><a name="l00110"></a><span class="lineno"> 110</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_PIN 4</span></div>
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<div class="line"><a name="l00111"></a><span class="lineno"> 111</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_CAPT_vect TIMER1_CAPT_vect</span></div>
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<div class="line"><a name="l00112"></a><span class="lineno"> 112</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_ICR ICR1</span></div>
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<div class="line"><a name="l00113"></a><span class="lineno"> 113</span> <span class="preprocessor"></span><span class="preprocessor">#else</span></div>
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<div class="line"><a name="l00114"></a><span class="lineno"> 114</span> <span class="preprocessor"></span><span class="comment">// Assuming Arduino Uno or equivalent - input capture on TIMER1 and D8/PB0.</span></div>
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<div class="line"><a name="l00115"></a><span class="lineno"> 115</span> <span class="preprocessor">#define RING_TIMER 1</span></div>
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<div class="line"><a name="l00116"></a><span class="lineno"> 116</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_PIN 8</span></div>
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<div class="line"><a name="l00117"></a><span class="lineno"> 117</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_CAPT_vect TIMER1_CAPT_vect</span></div>
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<div class="line"><a name="l00118"></a><span class="lineno"> 118</span> <span class="preprocessor"></span><span class="preprocessor">#define RING_ICR ICR1</span></div>
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<div class="line"><a name="l00119"></a><span class="lineno"> 119</span> <span class="preprocessor"></span><span class="preprocessor">#endif</span></div>
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<div class="line"><a name="l00120"></a><span class="lineno"> 120</span> <span class="preprocessor"></span></div>
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<div class="line"><a name="l00121"></a><span class="lineno"> 121</span> <span class="comment">// Calibration states.</span></div>
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<div class="line"><a name="l00122"></a><span class="lineno"> 122</span> <span class="preprocessor">#define NOISE_NOT_CALIBRATING 0</span></div>
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<div class="line"><a name="l00123"></a><span class="lineno"> 123</span> <span class="preprocessor"></span><span class="preprocessor">#define NOISE_CALIBRATING 1</span></div>
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<div class="line"><a name="l00124"></a><span class="lineno"> 124</span> <span class="preprocessor"></span></div>
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<div class="line"><a name="l00125"></a><span class="lineno"> 125</span> <span class="comment">// If there is no capture event for this many milliseconds,</span></div>
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<div class="line"><a name="l00126"></a><span class="lineno"> 126</span> <span class="comment">// then assume that the oscillator is stopped or disconnected.</span></div>
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<div class="line"><a name="l00127"></a><span class="lineno"> 127</span> <span class="preprocessor">#define RING_DISCONNECT_TIME 200</span></div>
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<div class="line"><a name="l00128"></a><span class="lineno"> 128</span> <span class="preprocessor"></span></div>
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<div class="line"><a name="l00129"></a><span class="lineno"> 129</span> RingOscillatorNoiseSource::RingOscillatorNoiseSource()</div>
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<div class="line"><a name="l00130"></a><span class="lineno"> 130</span>  : calState(NOISE_CALIBRATING)</div>
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<div class="line"><a name="l00131"></a><span class="lineno"> 131</span>  , lastSignal(millis())</div>
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<div class="line"><a name="l00132"></a><span class="lineno"> 132</span> {</div>
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<div class="line"><a name="l00133"></a><span class="lineno"> 133</span>  <span class="comment">// Initialize the bit collection routines.</span></div>
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<div class="line"><a name="l00134"></a><span class="lineno"> 134</span>  restart();</div>
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<div class="line"><a name="l00135"></a><span class="lineno"> 135</span> </div>
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<div class="line"><a name="l00136"></a><span class="lineno"> 136</span>  <span class="comment">// Set up the capture pin as an input with no pull-ups.</span></div>
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<div class="line"><a name="l00137"></a><span class="lineno"> 137</span>  pinMode(RING_PIN, INPUT);</div>
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<div class="line"><a name="l00138"></a><span class="lineno"> 138</span>  digitalWrite(RING_PIN, LOW);</div>
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<div class="line"><a name="l00139"></a><span class="lineno"> 139</span> </div>
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<div class="line"><a name="l00140"></a><span class="lineno"> 140</span> <span class="preprocessor">#if RING_TIMER == 1</span></div>
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<div class="line"><a name="l00141"></a><span class="lineno"> 141</span> <span class="preprocessor"></span> <span class="comment">// Set up TIMER1 to perform input capture on PB8/D8.</span></div>
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<div class="line"><a name="l00142"></a><span class="lineno"> 142</span>  TCCR1B = 0; <span class="comment">// Turn off TIMER1.</span></div>
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<div class="line"><a name="l00143"></a><span class="lineno"> 143</span>  TIMSK1 = 0; <span class="comment">// Turn off TIMER1 interrupts.</span></div>
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<div class="line"><a name="l00144"></a><span class="lineno"> 144</span>  TCNT1 = 0; <span class="comment">// Zero the timer.</span></div>
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<div class="line"><a name="l00145"></a><span class="lineno"> 145</span>  TCCR1A = 0; <span class="comment">// Turn off output compare.</span></div>
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<div class="line"><a name="l00146"></a><span class="lineno"> 146</span>  TCCR1B |= (1 << ICES1); <span class="comment">// Input capture on rising edge.</span></div>
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<div class="line"><a name="l00147"></a><span class="lineno"> 147</span>  TIMSK1 |= (1 << ICIE1); <span class="comment">// Input capture interrupts enabled.</span></div>
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<div class="line"><a name="l00148"></a><span class="lineno"> 148</span> </div>
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<div class="line"><a name="l00149"></a><span class="lineno"> 149</span>  <span class="comment">// Start TIMER1 at the highest frequency with no prescaling.</span></div>
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<div class="line"><a name="l00150"></a><span class="lineno"> 150</span>  TCCR1B |= (1 << CS10);</div>
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<div class="line"><a name="l00151"></a><span class="lineno"> 151</span> <span class="preprocessor">#elif RING_TIMER == 4</span></div>
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<div class="line"><a name="l00152"></a><span class="lineno"> 152</span> <span class="preprocessor"></span> <span class="comment">// Set up TIMER4 to perform input capture on PL0/D49.</span></div>
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<div class="line"><a name="l00153"></a><span class="lineno"> 153</span>  TCCR4B = 0; <span class="comment">// Turn off TIMER4.</span></div>
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<div class="line"><a name="l00154"></a><span class="lineno"> 154</span>  TIMSK4 = 0; <span class="comment">// Turn off TIMER4 interrupts.</span></div>
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<div class="line"><a name="l00155"></a><span class="lineno"> 155</span>  TCNT4 = 0; <span class="comment">// Zero the timer.</span></div>
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<div class="line"><a name="l00156"></a><span class="lineno"> 156</span>  TCCR4A = 0; <span class="comment">// Turn off output compare.</span></div>
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<div class="line"><a name="l00157"></a><span class="lineno"> 157</span>  TCCR4B |= (1 << ICES4); <span class="comment">// Input capture on rising edge.</span></div>
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<div class="line"><a name="l00158"></a><span class="lineno"> 158</span>  TIMSK4 |= (1 << ICIE4); <span class="comment">// Input capture interrupts enabled.</span></div>
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<div class="line"><a name="l00159"></a><span class="lineno"> 159</span> </div>
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<div class="line"><a name="l00160"></a><span class="lineno"> 160</span>  <span class="comment">// Start TIMER4 at the highest frequency with no prescaling.</span></div>
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<div class="line"><a name="l00161"></a><span class="lineno"> 161</span>  TCCR4B |= (1 << CS10);</div>
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<div class="line"><a name="l00162"></a><span class="lineno"> 162</span> <span class="preprocessor">#endif</span></div>
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<div class="line"><a name="l00163"></a><span class="lineno"> 163</span> <span class="preprocessor"></span>}</div>
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<div class="line"><a name="l00164"></a><span class="lineno"> 164</span> </div>
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<div class="line"><a name="l00165"></a><span class="lineno"> 165</span> RingOscillatorNoiseSource::~RingOscillatorNoiseSource()</div>
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<div class="line"><a name="l00166"></a><span class="lineno"> 166</span> {</div>
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<div class="line"><a name="l00167"></a><span class="lineno"> 167</span>  <span class="comment">// Turn off the capture timer.</span></div>
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<div class="line"><a name="l00168"></a><span class="lineno"> 168</span> <span class="preprocessor">#if RING_TIMER == 1</span></div>
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<div class="line"><a name="l00169"></a><span class="lineno"> 169</span> <span class="preprocessor"></span> TCCR1B = 0;</div>
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<div class="line"><a name="l00170"></a><span class="lineno"> 170</span> <span class="preprocessor">#elif RING_TIMER == 4</span></div>
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<div class="line"><a name="l00171"></a><span class="lineno"> 171</span> <span class="preprocessor"></span> TCCR4B = 0;</div>
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<div class="line"><a name="l00172"></a><span class="lineno"> 172</span> <span class="preprocessor">#endif</span></div>
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<div class="line"><a name="l00173"></a><span class="lineno"> 173</span> <span class="preprocessor"></span></div>
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<div class="line"><a name="l00174"></a><span class="lineno"> 174</span>  <span class="comment">// Clean up.</span></div>
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<div class="line"><a name="l00175"></a><span class="lineno"> 175</span>  clean(buffer);</div>
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<div class="line"><a name="l00176"></a><span class="lineno"> 176</span> }</div>
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<div class="line"><a name="l00177"></a><span class="lineno"> 177</span> </div>
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<div class="line"><a name="l00178"></a><span class="lineno"><a class="line" href="classRingOscillatorNoiseSource.html#ade7f7ed390e23722347b3c207912b3f9"> 178</a></span> <span class="keywordtype">bool</span> <a class="code" href="classRingOscillatorNoiseSource.html#ade7f7ed390e23722347b3c207912b3f9">RingOscillatorNoiseSource::calibrating</a>()<span class="keyword"> const</span></div>
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<div class="line"><a name="l00179"></a><span class="lineno"> 179</span> <span class="keyword"></span>{</div>
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<div class="line"><a name="l00180"></a><span class="lineno"> 180</span>  <span class="keywordflow">return</span> calState == NOISE_CALIBRATING;</div>
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<div class="line"><a name="l00181"></a><span class="lineno"> 181</span> }</div>
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<div class="line"><a name="l00182"></a><span class="lineno"> 182</span> </div>
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<div class="line"><a name="l00183"></a><span class="lineno"> 183</span> <span class="keyword">static</span> uint16_t <span class="keyword">volatile</span> out = 0;</div>
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<div class="line"><a name="l00184"></a><span class="lineno"> 184</span> <span class="keyword">static</span> uint8_t <span class="keyword">volatile</span> outBits = 0;</div>
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<div class="line"><a name="l00185"></a><span class="lineno"> 185</span> </div>
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<div class="line"><a name="l00186"></a><span class="lineno"> 186</span> <span class="comment">// Interrupt service routine for the timer's input capture interrupt.</span></div>
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<div class="line"><a name="l00187"></a><span class="lineno"> 187</span> ISR(RING_CAPT_vect)</div>
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<div class="line"><a name="l00188"></a><span class="lineno"> 188</span> {</div>
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<div class="line"><a name="l00189"></a><span class="lineno"> 189</span>  <span class="comment">// We are interested in the jitter; that is the difference in</span></div>
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<div class="line"><a name="l00190"></a><span class="lineno"> 190</span>  <span class="comment">// time between one rising edge and the next in the signal.</span></div>
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<div class="line"><a name="l00191"></a><span class="lineno"> 191</span>  <span class="comment">// Extract a single bit from the jitter and add it to the</span></div>
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<div class="line"><a name="l00192"></a><span class="lineno"> 192</span>  <span class="comment">// rolling "out" buffer for the main code to process later.</span></div>
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<div class="line"><a name="l00193"></a><span class="lineno"> 193</span>  <span class="comment">// If the buffer overflows, we discard bits and keep going.</span></div>
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<div class="line"><a name="l00194"></a><span class="lineno"> 194</span>  <span class="keyword">static</span> uint16_t prev = 0;</div>
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<div class="line"><a name="l00195"></a><span class="lineno"> 195</span>  uint16_t next = RING_ICR;</div>
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<div class="line"><a name="l00196"></a><span class="lineno"> 196</span>  out = (out << 1) | ((next - prev) & 1);</div>
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<div class="line"><a name="l00197"></a><span class="lineno"> 197</span>  prev = next;</div>
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<div class="line"><a name="l00198"></a><span class="lineno"> 198</span>  ++outBits;</div>
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<div class="line"><a name="l00199"></a><span class="lineno"> 199</span> }</div>
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<div class="line"><a name="l00200"></a><span class="lineno"> 200</span> </div>
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<div class="line"><a name="l00201"></a><span class="lineno"><a class="line" href="classRingOscillatorNoiseSource.html#ad71698b5c92b41eef2f1322999b3eff9"> 201</a></span> <span class="keywordtype">void</span> <a class="code" href="classRingOscillatorNoiseSource.html#ad71698b5c92b41eef2f1322999b3eff9">RingOscillatorNoiseSource::stir</a>()</div>
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<div class="line"><a name="l00202"></a><span class="lineno"> 202</span> {</div>
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<div class="line"><a name="l00203"></a><span class="lineno"> 203</span>  <span class="comment">// If the "out" buffer is full, then convert the bits. Turn off</span></div>
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<div class="line"><a name="l00204"></a><span class="lineno"> 204</span>  <span class="comment">// interrupts while we read the "out" buffer and reset "outBits".</span></div>
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<div class="line"><a name="l00205"></a><span class="lineno"> 205</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> now = millis();</div>
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<div class="line"><a name="l00206"></a><span class="lineno"> 206</span>  cli();</div>
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<div class="line"><a name="l00207"></a><span class="lineno"> 207</span>  <span class="keywordflow">if</span> (outBits >= 16) {</div>
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<div class="line"><a name="l00208"></a><span class="lineno"> 208</span>  uint16_t bits = out;</div>
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<div class="line"><a name="l00209"></a><span class="lineno"> 209</span>  outBits = 0;</div>
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<div class="line"><a name="l00210"></a><span class="lineno"> 210</span>  sei();</div>
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<div class="line"><a name="l00211"></a><span class="lineno"> 211</span>  <span class="keywordflow">for</span> (uint8_t index = 0; index < 8; ++index) {</div>
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<div class="line"><a name="l00212"></a><span class="lineno"> 212</span>  <span class="comment">// Collect two bits of input and remove bias using the Von Neumann</span></div>
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<div class="line"><a name="l00213"></a><span class="lineno"> 213</span>  <span class="comment">// method. If both bits are the same, then discard both.</span></div>
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<div class="line"><a name="l00214"></a><span class="lineno"> 214</span>  <span class="comment">// Otherwise choose one of the bits and output that one.</span></div>
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<div class="line"><a name="l00215"></a><span class="lineno"> 215</span>  <span class="comment">// We have to do this carefully so that instruction timing does</span></div>
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<div class="line"><a name="l00216"></a><span class="lineno"> 216</span>  <span class="comment">// not reveal the value of the bit that is chosen.</span></div>
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<div class="line"><a name="l00217"></a><span class="lineno"> 217</span>  <span class="keywordflow">if</span> ((bits ^ (bits << 1)) & 0x8000) {</div>
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<div class="line"><a name="l00218"></a><span class="lineno"> 218</span>  <span class="comment">// The bits are different: add the top-most to the buffer.</span></div>
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<div class="line"><a name="l00219"></a><span class="lineno"> 219</span>  <span class="keywordflow">if</span> (posn < <span class="keyword">sizeof</span>(buffer)) {</div>
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<div class="line"><a name="l00220"></a><span class="lineno"> 220</span>  buffer[posn] = (buffer[posn] >> 1) |</div>
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<div class="line"><a name="l00221"></a><span class="lineno"> 221</span>  (((uint8_t)(bits >> 8)) & (uint8_t)0x80);</div>
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<div class="line"><a name="l00222"></a><span class="lineno"> 222</span>  <span class="keywordflow">if</span> (++bitNum >= 8) {</div>
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<div class="line"><a name="l00223"></a><span class="lineno"> 223</span>  ++posn;</div>
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<div class="line"><a name="l00224"></a><span class="lineno"> 224</span>  bitNum = 0;</div>
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<div class="line"><a name="l00225"></a><span class="lineno"> 225</span>  }</div>
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<div class="line"><a name="l00226"></a><span class="lineno"> 226</span>  }</div>
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<div class="line"><a name="l00227"></a><span class="lineno"> 227</span>  }</div>
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<div class="line"><a name="l00228"></a><span class="lineno"> 228</span>  bits = bits << 2;</div>
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<div class="line"><a name="l00229"></a><span class="lineno"> 229</span>  }</div>
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<div class="line"><a name="l00230"></a><span class="lineno"> 230</span>  } <span class="keywordflow">else</span> {</div>
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<div class="line"><a name="l00231"></a><span class="lineno"> 231</span>  <span class="comment">// The "out" buffer isn't full yet. Re-enable interrupts.</span></div>
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<div class="line"><a name="l00232"></a><span class="lineno"> 232</span>  sei();</div>
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<div class="line"><a name="l00233"></a><span class="lineno"> 233</span> </div>
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<div class="line"><a name="l00234"></a><span class="lineno"> 234</span>  <span class="comment">// If it has been too long since the last useful block,</span></div>
|
|
<div class="line"><a name="l00235"></a><span class="lineno"> 235</span>  <span class="comment">// then go back to calibrating. The oscillator may be</span></div>
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<div class="line"><a name="l00236"></a><span class="lineno"> 236</span>  <span class="comment">// stopped or disconnected.</span></div>
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<div class="line"><a name="l00237"></a><span class="lineno"> 237</span>  <span class="keywordflow">if</span> (calState == NOISE_NOT_CALIBRATING) {</div>
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<div class="line"><a name="l00238"></a><span class="lineno"> 238</span>  <span class="keywordflow">if</span> ((now - lastSignal) >= RING_DISCONNECT_TIME) {</div>
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<div class="line"><a name="l00239"></a><span class="lineno"> 239</span>  restart();</div>
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<div class="line"><a name="l00240"></a><span class="lineno"> 240</span>  calState = NOISE_CALIBRATING;</div>
|
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<div class="line"><a name="l00241"></a><span class="lineno"> 241</span>  }</div>
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<div class="line"><a name="l00242"></a><span class="lineno"> 242</span>  }</div>
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<div class="line"><a name="l00243"></a><span class="lineno"> 243</span>  }</div>
|
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<div class="line"><a name="l00244"></a><span class="lineno"> 244</span> </div>
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<div class="line"><a name="l00245"></a><span class="lineno"> 245</span>  <span class="comment">// If the buffer is full, then stir it into the random number pool.</span></div>
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|
<div class="line"><a name="l00246"></a><span class="lineno"> 246</span>  <span class="comment">// We credit 1 bit of entropy for every 8 bits of output because</span></div>
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<div class="line"><a name="l00247"></a><span class="lineno"> 247</span>  <span class="comment">// ring oscillators aren't quite as good as a true noise source.</span></div>
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<div class="line"><a name="l00248"></a><span class="lineno"> 248</span>  <span class="comment">// We have to collect a lot more data to get something random enough.</span></div>
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<div class="line"><a name="l00249"></a><span class="lineno"> 249</span>  <span class="keywordflow">if</span> (posn >= <span class="keyword">sizeof</span>(buffer)) {</div>
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<div class="line"><a name="l00250"></a><span class="lineno"> 250</span>  <a class="code" href="classNoiseSource.html#a1af7449a5ae4a8acd34ac218c9eec6c1">output</a>(buffer, posn, posn);</div>
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<div class="line"><a name="l00251"></a><span class="lineno"> 251</span>  restart();</div>
|
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<div class="line"><a name="l00252"></a><span class="lineno"> 252</span>  calState = NOISE_NOT_CALIBRATING;</div>
|
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<div class="line"><a name="l00253"></a><span class="lineno"> 253</span>  lastSignal = now;</div>
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<div class="line"><a name="l00254"></a><span class="lineno"> 254</span>  }</div>
|
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<div class="line"><a name="l00255"></a><span class="lineno"> 255</span> }</div>
|
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<div class="line"><a name="l00256"></a><span class="lineno"> 256</span> </div>
|
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<div class="line"><a name="l00257"></a><span class="lineno"> 257</span> <span class="keywordtype">void</span> RingOscillatorNoiseSource::restart()</div>
|
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<div class="line"><a name="l00258"></a><span class="lineno"> 258</span> {</div>
|
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<div class="line"><a name="l00259"></a><span class="lineno"> 259</span>  clean(buffer);</div>
|
|
<div class="line"><a name="l00260"></a><span class="lineno"> 260</span>  prevBit = 0;</div>
|
|
<div class="line"><a name="l00261"></a><span class="lineno"> 261</span>  posn = 0;</div>
|
|
<div class="line"><a name="l00262"></a><span class="lineno"> 262</span>  bitNum = 0;</div>
|
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<div class="line"><a name="l00263"></a><span class="lineno"> 263</span> }</div>
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<div class="ttc" id="classRingOscillatorNoiseSource_html_ad71698b5c92b41eef2f1322999b3eff9"><div class="ttname"><a href="classRingOscillatorNoiseSource.html#ad71698b5c92b41eef2f1322999b3eff9">RingOscillatorNoiseSource::stir</a></div><div class="ttdeci">void stir()</div><div class="ttdoc">Stirs entropy from this noise source into the global random number pool. </div><div class="ttdef"><b>Definition:</b> <a href="RingOscillatorNoiseSource_8cpp_source.html#l00201">RingOscillatorNoiseSource.cpp:201</a></div></div>
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<div class="ttc" id="classRingOscillatorNoiseSource_html_ade7f7ed390e23722347b3c207912b3f9"><div class="ttname"><a href="classRingOscillatorNoiseSource.html#ade7f7ed390e23722347b3c207912b3f9">RingOscillatorNoiseSource::calibrating</a></div><div class="ttdeci">bool calibrating() const </div><div class="ttdoc">Determine if the noise source is still calibrating itself. </div><div class="ttdef"><b>Definition:</b> <a href="RingOscillatorNoiseSource_8cpp_source.html#l00178">RingOscillatorNoiseSource.cpp:178</a></div></div>
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<div class="ttc" id="classNoiseSource_html_a1af7449a5ae4a8acd34ac218c9eec6c1"><div class="ttname"><a href="classNoiseSource.html#a1af7449a5ae4a8acd34ac218c9eec6c1">NoiseSource::output</a></div><div class="ttdeci">virtual void output(const uint8_t *data, size_t len, unsigned int credit)</div><div class="ttdoc">Called from subclasses to output noise to the global random number pool. </div><div class="ttdef"><b>Definition:</b> <a href="NoiseSource_8cpp_source.html#l00117">NoiseSource.cpp:117</a></div></div>
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