FastShiftIn.cpp

//
//    FILE: FastShiftIn.cpp
//  AUTHOR: Rob Tillaart
// VERSION: 0.4.0
// PURPOSE: Fast ShiftIn for 74HC165 register, AVR optimized
//    DATE: 2013-09-29
//     URL: https://github.com/RobTillaart/FastShiftIn


#include "FastShiftIn.h"


FastShiftIn::FastShiftIn(uint8_t dataIn, uint8_t clockPin, uint8_t bitOrder)
{
  _bitOrder  = bitOrder;
  _lastValue = 0;
  pinMode(dataIn, INPUT);
  pinMode(clockPin, OUTPUT);
  //  https://www.arduino.cc/reference/en/language/functions/advanced-io/shiftin/
  digitalWrite(clockPin, LOW);  //  assume rising pulses from clock

#if defined(ARDUINO_ARCH_AVR) || defined(ARDUINO_ARCH_MEGAAVR)

  uint8_t _port    = digitalPinToPort(dataIn);
  _dataInRegister  = portInputRegister(_port);
  _dataInBit       = digitalPinToBitMask(dataIn);

  _port            = digitalPinToPort(clockPin);
  _clockRegister   = portOutputRegister(_port);
  _clockBit        = digitalPinToBitMask(clockPin);

#else

  _dataPinIn  = dataIn;
  _clockPin   = clockPin;

#endif

}


uint16_t FastShiftIn::read()
{
  if (_bitOrder == LSBFIRST)
  {
    return readLSBFIRST();
  }
  return readMSBFIRST();
}


uint16_t FastShiftIn::read16()
{
  if (_bitOrder == LSBFIRST)
  {
    uint16_t rv = readLSBFIRST();
    rv += uint16_t(readLSBFIRST()) << 8;
    return rv;
  }
  uint16_t rv = readMSBFIRST();
  rv <<= 8;
  rv += readMSBFIRST();
  return rv;
}


uint32_t FastShiftIn::read24()
{
  if (_bitOrder == LSBFIRST)
  {
    uint32_t rv = readLSBFIRST();
    rv += uint32_t(readLSBFIRST()) << 8;
    rv += uint32_t(readLSBFIRST()) << 16;
    return rv;
  }
  uint32_t rv = readMSBFIRST();
  rv <<= 8;
  rv += readMSBFIRST();
  rv <<= 8;
  rv += readMSBFIRST();
  return rv;
}


uint32_t FastShiftIn::read32()
{
  if (_bitOrder == LSBFIRST)
  {
    uint32_t rv = readLSBFIRST();
    rv += uint32_t(readLSBFIRST()) << 8;
    rv += uint32_t(readLSBFIRST()) << 16;
    rv += uint32_t(readLSBFIRST()) << 24;
    return rv;
  }
  uint32_t rv = readMSBFIRST();
  rv <<= 8;
  rv += readMSBFIRST();
  rv <<= 8;
  rv += readMSBFIRST();
  rv <<= 8;
  rv += readMSBFIRST();
  return rv;
}


uint32_t FastShiftIn::lastRead(void)
{
  return _lastValue;
}


void FastShiftIn::read(uint8_t * array, uint8_t size)
{
  if (_bitOrder == LSBFIRST)
  {
    for (uint8_t i = 0; i < size; i++)
    {
      array[size - i - 1] = readLSBFIRST();
    }
    return;
  }
  for (uint8_t i = 0; i < size; i++)
  {
    array[i] = readMSBFIRST();
  }
  return;
}


bool FastShiftIn::setBitOrder(const uint8_t bitOrder)
{
  if ((bitOrder == LSBFIRST) || (bitOrder == MSBFIRST))
  {
    _bitOrder = bitOrder;
    return true;
  };
  return false;
}


uint8_t FastShiftIn::getBitOrder(void)
{
  return _bitOrder;
}


uint8_t FastShiftIn::readLSBFIRST()
{
#if defined(ARDUINO_ARCH_AVR) || defined(ARDUINO_ARCH_MEGAAVR)

#if defined(FASTSHIFTIN_AVR_LOOP_UNROLLED)  //  AVR SPEED OPTIMIZED  #17

  uint8_t rv      = 0;
  uint8_t cbmask1 = _clockBit;
  uint8_t inmask1 = _dataInBit;

  volatile uint8_t* localDataInRegister = _dataInRegister;
  volatile uint8_t* localClockRegister  = _clockRegister;

  //  disable interrupts (for all bits)
  uint8_t oldSREG = SREG;
  noInterrupts();

  uint8_t r = *localClockRegister;
  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x01;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x02;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x04;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x08;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x10;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x20;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x40;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x80;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  //  restore interrupt state
  SREG = oldSREG;

  _lastValue = rv;

#else  //  AVR SIZE OPTIMIZED

  uint8_t rv       = 0;
  uint8_t cbmask1  = _clockBit;
  uint8_t inmask1  = _dataInBit;

  volatile uint8_t* localDataInRegister = _dataInRegister;
  volatile uint8_t* localClockRegister = _clockRegister;

  //  disable interrupts (for all bits)
  uint8_t oldSREG = SREG;
  noInterrupts();

  uint8_t r = *localClockRegister;

  for (uint8_t m = 0x01; m > 0; m <<= 1)
  {
    //  clock pulse HIGH
    *localClockRegister |= cbmask1;
    //  read one bit
    if ((*localDataInRegister & inmask1) > 0) rv |= m;
    //  clock pulse LOW
    *localClockRegister = r;
  }

  //  reset interrupts flag to previous state
  SREG = oldSREG;

  _lastValue = rv;

#endif  //  if (AVR)

#else   //  other platforms reference shiftOut()

  //  reference implementation
  _lastValue = shiftIn(_dataPinIn, _clockPin, LSBFIRST);

#endif

  //  all paths will return _lastValue.
  return _lastValue;
}


uint8_t FastShiftIn::readMSBFIRST()
{
#if defined(ARDUINO_ARCH_AVR) || defined(ARDUINO_ARCH_MEGAAVR)

#if defined(FASTSHIFTIN_AVR_LOOP_UNROLLED)  //  AVR SPEED OPTIMIZED

  uint8_t rv      = 0;
  uint8_t cbmask1 = _clockBit;
  uint8_t inmask1 = _dataInBit;

  volatile uint8_t* localDataInRegister = _dataInRegister;
  volatile uint8_t* localClockRegister  = _clockRegister;

  //  disable interrupts (for all bits)
  uint8_t oldSREG = SREG;
  noInterrupts();

  uint8_t r = *localClockRegister;
  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x80;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x40;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x20;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x10;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x08;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x04;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x02;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  *localClockRegister |= cbmask1;  //  clock pulse HIGH
  if ((*localDataInRegister & inmask1) > 0) rv |= 0x01;  //  read one bit
  *localClockRegister = r;         //  clock pulse LOW

  //  restore interrupt state
  SREG = oldSREG;

  _lastValue = rv;

#else  //  AVR SIZE OPTIMIZED

  uint8_t rv      = 0;
  uint8_t cbmask1 = _clockBit;
  uint8_t inmask1 = _dataInBit;

  volatile uint8_t* localDataInRegister = _dataInRegister;
  volatile uint8_t* localClockRegister  = _clockRegister;

  //  disable interrupts (for all bits)
  uint8_t oldSREG = SREG;
  noInterrupts();

  uint8_t r = *localClockRegister;
  for (uint8_t m = 0x80; m > 0; m >>= 1)
  {
    //  clock pulse HIGH
    *localClockRegister |= cbmask1;
    //  read one bit
    if ((*localDataInRegister & inmask1) > 0) rv |= m;
    //  clock pulse LOW
    *localClockRegister = r;
  }

  //  reset interrupts flag to previous state
  SREG = oldSREG;

  _lastValue = rv;

#endif  //  if (AVR)

#else   //  other platforms reference shiftOut()

  //  reference implementation
  _lastValue = shiftIn(_dataPinIn, _clockPin, MSBFIRST);

#endif

  //  all paths will return _lastValue.
  return _lastValue;
}


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