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‎FastShiftIn.cpp

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//
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// FILE: FastShiftIn.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.2.0
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// PURPOSE: Fast ShiftIn for 74HC165 register, AVR optimized
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// DATE: 2013-09-29
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// URL: https://github.com/RobTillaart/FastShiftIn.git
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//
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#include "FastShiftIn.h"
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FastShiftIn::FastShiftIn(const uint8_t datapin, const uint8_t clockpin, const uint8_t bitOrder)
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{
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_bitorder = bitOrder;
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pinMode(datapin, INPUT);
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pinMode(clockpin, INPUT);
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// uint8_t _datatimer = digitalPinToTimer(datapin);
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// if (_datatimer != NOT_ON_TIMER) turnOffPWM(_datatimer); TODO
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uint8_t _dataport = digitalPinToPort(datapin);
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_datain = portOutputRegister(_dataport);
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_databit = digitalPinToBitMask(datapin);
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// uint8_t _clocktimer = digitalPinToTimer(clockpin);
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// if (_clocktimer != NOT_ON_TIMER) turnOffPWM(_clocktimer);
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uint8_t _clockport = digitalPinToPort(clockpin);
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_clockin = portOutputRegister(_clockport);
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_clockbit = digitalPinToBitMask(clockpin);
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}
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int FastShiftIn::read()
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{
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uint8_t value = 0;
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uint8_t cbmask1 = _clockbit;
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uint8_t cbmask2 = ~_clockbit;
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uint8_t dbmask = _databit;
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for (uint8_t i = 0, m = 1, n = 128; i < 8; i++, m <<= 1, n >>= 1)
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{
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uint8_t oldSREG = SREG;
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cli();
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*_clockin |= cbmask1;
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if ((*_datain & dbmask) > 0)
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{
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if (_bitorder == LSBFIRST)
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{
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value |= m;
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}
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else
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{
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value |= n;
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}
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}
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*_clockin &= cbmask2;
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SREG = oldSREG;
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}
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_value = value;
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return _value;
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}
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int FastShiftIn::readLSBFIRST()
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{
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uint8_t value = 0;
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uint8_t cbmask1 = _clockbit;
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uint8_t cbmask2 = ~_clockbit;
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uint8_t dbmask = _databit;
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for (uint8_t m = 1; m > 0; m <<= 1)
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{
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uint8_t oldSREG = SREG;
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cli();
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*_clockin |= cbmask1;
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if ((*_datain & dbmask) > 0)
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{
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value |= m;
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}
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*_clockin &= cbmask2;
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SREG = oldSREG;
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}
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_value = value;
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return _value;
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}
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int FastShiftIn::readMSBFIRST()
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{
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uint8_t value = 0;
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uint8_t cbmask1 = _clockbit;
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uint8_t cbmask2 = ~cbmask1;
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uint8_t dbmask = _databit;
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for (uint8_t n = 128; n > 0; n >>= 1)
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{
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uint8_t oldSREG = SREG;
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cli();
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*_clockin |= cbmask1;
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if ((*_datain & dbmask) > 0)
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{
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value |= n;
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}
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*_clockin &= cbmask2;
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SREG = oldSREG;
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}
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_value = value;
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return _value;
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}
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// -- END OF FILE --

‎FastShiftIn.h

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#pragma once
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//
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// FILE: FastShiftIn.h
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// AUTHOR: Rob Tillaart
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// VERSION: 0.2.0
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// PURPOSE: Fast ShiftIn for 74HC165 register, AVR optimized
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// DATE: 2013-09-29
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// URL: https://github.com/RobTillaart/FastShiftIn.git
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//
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#if defined(ARDUINO_ARCH_AVR) || defined(ARDUINO_ARCH_MEGAAVR)
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#else
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#error "FastShiftIn: only AVR supported,"
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#endif
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#include "Arduino.h"
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#define FASTSHIFTIN_LIB_VERSION "0.2.0"
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class FastShiftIn
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{
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public:
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// bitorder = { LSBFIRST, MSBFIRST }; // bitorder will become obsolete in the future
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FastShiftIn(const uint8_t datapin, const uint8_t clockpin, const uint8_t bitOrder = LSBFIRST);
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// read() will become obsolete in the future
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int read(void);
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// overrule bitorder (most optimized).
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int readLSBFIRST(void);
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int readMSBFIRST(void);
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private:
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uint8_t _bitorder;
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int _value;
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uint8_t _databit;
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volatile uint8_t *_datain;
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uint8_t _clockbit;
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volatile uint8_t *_clockin;
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};
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// -- END OF FILE --

‎LICENSE

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MIT License
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3-
Copyright (c) 2020 Rob Tillaart
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Copyright (c) 2013-2020 Rob Tillaart
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal

‎README.md

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# FastShiftIn
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Arduino library for (AVR) optimized shiftIn - e.g. 74HC165
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Arduino library for (AVR) optimized shiftIn - e.g. for 74HC165
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A library for FastShiftOut also exist.
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## Description
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FastShiftIn is a class that speeds up the shifting of the bits by using predetermined ports and masks.
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These are predetermined inthe constructor of the FastShiftIN object.
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The performance of **read()** is substantially faster than the default Arduino **shiftIn()**,
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but not as fast as HW SPI. Exact how big the performance gain is can be seen with the example sketch.
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It does a comparison and shows how the class is to be used.
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Version 0.2.0 added **readLSBFIRST()** and **readMSBFIRST()** to squeeze max performance.
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The next stop might be assembly.
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**Note**
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The optimizations are AVR only for now, other platforms may follow.
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**Note**
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The 74HC165 needs 0.1uF caps and the data and clock lines
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may need pull up resistors, especially if wires are exceeding 10 cm (4").
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## Operation
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See examples
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‎examples/fastShiftIn/fastShiftIn.ino

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//
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// FILE: fastShiftIn.ino
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.01
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// PURPOSE: test sketch
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// URL:
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//
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// Released to the public domain
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//
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#include "FastShiftIn.h"
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FastShiftIn FSI(12, 13, LSBFIRST);
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volatile int x = 0;
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void setup()
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{
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Serial.begin(115200);
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Serial.print("example fastShiftIn: ");
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Serial.println(FASTSHIFTIN_LIB_VERSION);
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digitalWrite(12, HIGH);
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Serial.println("\n 8 bits HIGH\n");
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Serial.println("\nPerformance - time in us");
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uint32_t start = micros();
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for (int i=0; i<1000; i++)
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{
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x = FSI.read();
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}
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uint32_t duration1 = micros() - start;
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Serial.print("FastShiftIn1: ");
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Serial.println(duration1 * 0.001);
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start = micros();
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for (int i=0; i<1000; i++)
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{
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x = FSI.read();
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x = FSI.read();
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}
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uint32_t duration2 = micros() - start;
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Serial.print("FastShiftIn2: ");
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Serial.println(duration2 * 0.001);
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Serial.print(" Delta: ");
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Serial.println((duration2-duration1)* 0.001);
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Serial.println();
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start = micros();
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for (int i=0; i<1000; i++)
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{
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x = shiftIn(12, 13, LSBFIRST);
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}
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duration1 = micros() - start;
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Serial.print("Standard shiftIn1: ");
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Serial.println(duration1* 0.001);
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start = micros();
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for (int i=0; i<1000; i++)
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{
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x = shiftIn(12, 13, LSBFIRST);
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x = shiftIn(12, 13, LSBFIRST);
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}
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duration2 = micros() - start;
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Serial.print("Standard shiftIn2: ");
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Serial.println(duration2 * 0.001);
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Serial.print(" Delta: ");
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Serial.println((duration2-duration1) * 0.001);
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Serial.println();
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Serial.println("done...");
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}
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void loop()
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{
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}

‎examples/fastShiftIn_readLSBFIRST/fastShiftIn_readLSBFIRST.ino

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//
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// FILE: fastShiftIn_readLSBFIRST.ino
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.0
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// PURPOSE: test sketch
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// URL: https://github.com/RobTillaart/FastShiftIn
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//
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#include "FastShiftIn.h"
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FastShiftIn FSI(12, 13);
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volatile int x = 0;
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void setup()
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{
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Serial.begin(115200);
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Serial.print("example fastShiftIn: ");
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Serial.println(FASTSHIFTIN_LIB_VERSION);
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digitalWrite(12, HIGH);
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Serial.println("\n 8 bits HIGH - readLSBFIRST\n");
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Serial.println("\nPerformance - time in us");
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uint32_t start = micros();
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for (int i = 0; i < 1000; i++)
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{
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x = FSI.readLSBFIRST();
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}
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uint32_t duration1 = micros() - start;
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Serial.print("FastShiftIn1: ");
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Serial.println(duration1 * 0.001);
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start = micros();
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for (int i = 0; i < 1000; i++)
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{
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x = FSI.readLSBFIRST();
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x = FSI.readLSBFIRST();
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}
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uint32_t duration2 = micros() - start;
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Serial.print("FastShiftIn2: ");
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Serial.println(duration2 * 0.001);
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Serial.print(" Delta: ");
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Serial.println((duration2 - duration1) * 0.001);
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Serial.println();
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start = micros();
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for (int i = 0; i < 1000; i++)
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{
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x = shiftIn(12, 13, LSBFIRST);
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}
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duration1 = micros() - start;
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Serial.print("Standard shiftIn1: ");
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Serial.println(duration1 * 0.001);
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start = micros();
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for (int i = 0; i < 1000; i++)
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{
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x = shiftIn(12, 13, LSBFIRST);
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x = shiftIn(12, 13, LSBFIRST);
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}
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duration2 = micros() - start;
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Serial.print("Standard shiftIn2: ");
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Serial.println(duration2 * 0.001);
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Serial.print(" Delta: ");
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Serial.println((duration2 - duration1) * 0.001);
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Serial.println();
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Serial.println("done...");
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}
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void loop()
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{
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}
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// -- END OF FILE --

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