endolith · January 14, 2024 07:37 · jbellows · Jun 13, 2016 · NoggetGump · Jul 18, 2016
diff --git a/readme.md b/readme.md
diff --git a/LICENSE.txt b/LICENSE.txt
 MIT License

 Copyright (c) 2012 endolith

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
diff --git a/probably_random.ino b/probably_random.ino
 #include <stdint.h>
 #include <avr/interrupt.h>
 #include <avr/wdt.h>

 byte sample = 0;
 boolean sample_waiting = false;
 byte current_bit = 0;
 byte result = 0;

 void setup() {
  Serial.begin(115200);
  wdtSetup();
 }

 void loop()
 {
  if (sample_waiting) {
    sample_waiting = false;

    result = rotl(result, 1); // Spread randomness around
    result ^= sample; // XOR preserves randomness

    current_bit++;
    if (current_bit > 7)
    {
      current_bit = 0;
      Serial.write(result); // raw binary
    }
  }
 }

 // Rotate bits to the left
 // https://en.wikipedia.org/wiki/Circular_shift#Implementing_circular_shifts
 byte rotl(const byte value, int shift) {
  if ((shift &= sizeof(value)*8 - 1) == 0)
    return value;
  return (value << shift) | (value >> (sizeof(value)*8 - shift));
 }

 // Setup of the watchdog timer.
 void wdtSetup() {
  cli();
  MCUSR = 0;
  
  /* Start timed sequence */
  WDTCSR |= _BV(WDCE) | _BV(WDE);

  /* Put WDT into interrupt mode */
  /* Set shortest prescaler(time-out) value = 2048 cycles (~16 ms) */
  WDTCSR = _BV(WDIE);

  sei();
 }

 // Watchdog Timer Interrupt Service Routine
 ISR(WDT_vect)
 {
  sample = TCNT1L; // Ignore higher bits
  sample_waiting = true;
 }
diff --git a/probably_random_with_TimerOne.ino b/probably_random_with_TimerOne.ino
 #include <stdint.h>
 #include <avr/interrupt.h>
 #include <avr/wdt.h>
 #include <TimerOne.h>

 byte sample = 0;
 boolean sample_waiting = false;
 byte current_bit = 0;
 byte result = 0;

 void setup() {
  Serial.begin(115200);
  wdtSetup();
  Timer1.initialize(30000); // set a timer of length somewhat longer than watchdog length
 }

 void loop()
 {
  if (sample_waiting) {
    sample_waiting = false;

    result = rotl(result, 1); // Spread randomness around
    result ^= sample; // XOR preserves randomness

    current_bit++;
    if (current_bit > 7)
    {
      current_bit = 0;
      Serial.write(result); // raw binary
      //Serial.println(result, DEC); // decimal text
      //binprint(result);  // bits
    }
  }
 }

 // Rotate bits to the left
 // https://en.wikipedia.org/wiki/Circular_shift#Implementing_circular_shifts
 byte rotl(const byte value, int shift) {
  if ((shift &= sizeof(value)*8 - 1) == 0)
    return value;
  return (value << shift) | (value >> (sizeof(value)*8 - shift));
 }

 // Setup of the watchdog timer.
 void wdtSetup() {
  cli();
  MCUSR = 0;
  
  /* Start timed sequence */
  WDTCSR |= _BV(WDCE) | _BV(WDE);

  /* Put WDT into interrupt mode */
  /* Set shortest prescaler(time-out) value = 2048 cycles (~16 ms) */
  WDTCSR = _BV(WDIE);

  sei();
 }

 // Watchdog Timer Interrupt
 ISR(WDT_vect)
 {
  sample = TCNT1L; // Ignore higher bits
  TCNT1 = 0; // Clear Timer 1
  sample_waiting = true;
 }

 // Print binary numbers
 // http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1193507343/5#5
 void binprint(int input) {
  for (unsigned int mask = 0x80; mask; mask >>= 1) {
    Serial.print(mask&input?'1':'0');
  }
  Serial.println();
 }
diff --git a/tester.py b/tester.py
 # -*- coding: utf-8 -*-

 from __future__ import division
 import serial
 from pylab import *
 from time import time
 import Image

 size = 2**16

 with serial.Serial('COM6', 115200) as port:
    start_time = time()
    data += port.read(size)
    elapsed_time = time() - start_time

 print 'Read ' + str(size) + ' bytes in ' + str(int(round(elapsed_time))) + ' s'
 print 'Data rate: %.1f bit/s' % (size*8 / elapsed_time)

 # Binary dump
 with open(str(int(time())) + 'out.bin','wb') as f:
    f.write(data)

 a = numpy.fromstring(data, dtype = 'uint8')

 # Plot
 figure()
 plot(a, 'bo', alpha=0.1) # Transparent to show stackups

 # Histogram
 figure()
 hist(a, bins=64, range=[0,255])

 # Image
 repeat = int(sqrt(size))
 b = reshape(a[:len(a) - len(a)%repeat], (-1, repeat))
 im = Image.fromarray(b)
 im.save(str(int(time())) + 'out.png')
	MIT License

	Copyright (c) 2012 endolith

	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:

	The above copyright notice and this permission notice shall be included in all
	copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	SOFTWARE.
	#include <stdint.h>
	#include <avr/interrupt.h>
	#include <avr/wdt.h>

	byte sample = 0;
	boolean sample_waiting = false;
	byte current_bit = 0;
	byte result = 0;

	void setup() {
	Serial.begin(115200);
	wdtSetup();
	}

	void loop()
	{
	if (sample_waiting) {
	sample_waiting = false;

	result = rotl(result, 1); // Spread randomness around
	result ^= sample; // XOR preserves randomness

	current_bit++;
	if (current_bit > 7)
	{
	current_bit = 0;
	Serial.write(result); // raw binary
	}
	}
	}

	// Rotate bits to the left
	// https://en.wikipedia.org/wiki/Circular_shift#Implementing_circular_shifts
	byte rotl(const byte value, int shift) {
	if ((shift &= sizeof(value)*8 - 1) == 0)
	return value;
	return (value << shift) \| (value >> (sizeof(value)*8 - shift));
	}

	// Setup of the watchdog timer.
	void wdtSetup() {
	cli();
	MCUSR = 0;

	/* Start timed sequence */
	WDTCSR \|= _BV(WDCE) \| _BV(WDE);

	/* Put WDT into interrupt mode */
	/* Set shortest prescaler(time-out) value = 2048 cycles (~16 ms) */
	WDTCSR = _BV(WDIE);

	sei();
	}

	// Watchdog Timer Interrupt Service Routine
	ISR(WDT_vect)
	{
	sample = TCNT1L; // Ignore higher bits
	sample_waiting = true;
	}
	# -- coding: utf-8 --

	from __future__ import division
	import serial
	from pylab import *
	from time import time
	import Image

	size = 2**16

	with serial.Serial('COM6', 115200) as port:
	start_time = time()
	data += port.read(size)
	elapsed_time = time() - start_time

	print 'Read ' + str(size) + ' bytes in ' + str(int(round(elapsed_time))) + ' s'
	print 'Data rate: %.1f bit/s' % (size*8 / elapsed_time)

	# Binary dump
	with open(str(int(time())) + 'out.bin','wb') as f:
	f.write(data)

	a = numpy.fromstring(data, dtype = 'uint8')

	# Plot
	figure()
	plot(a, 'bo', alpha=0.1) # Transparent to show stackups

	# Histogram
	figure()
	hist(a, bins=64, range=[0,255])

	# Image
	repeat = int(sqrt(size))
	b = reshape(a[:len(a) - len(a)%repeat], (-1, repeat))
	im = Image.fromarray(b)
	im.save(str(int(time())) + 'out.png')