mirror of
https://github.com/RobTillaart/Arduino.git
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122 lines
1.9 KiB
C++
122 lines
1.9 KiB
C++
//
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// FILE: CRC16.cpp
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// AUTHOR: Rob Tillaart
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// PURPOSE: Arduino class for CRC16
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// URL: https://github.com/RobTillaart/CRC
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#include "CRC16.h"
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CRC16::CRC16()
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{
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reset();
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}
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CRC16::CRC16(uint16_t polynome, uint16_t XORstart, uint16_t XORend, bool reverseIn, bool reverseOut)
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{
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_polynome = polynome;
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_startMask = XORstart;
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_endMask = XORend;
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_reverseIn = reverseIn;
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_reverseOut = reverseOut;
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_crc = 0;
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_started = false;
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_count = 0;
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_canYield = true;
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}
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void CRC16::reset()
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{
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_polynome = CRC16_DEFAULT_POLYNOME;
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_startMask = 0;
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_endMask = 0;
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_crc = 0;
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_reverseIn = false;
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_reverseOut = false;
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_started = false;
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_count = 0;
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_canYield = true;
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}
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void CRC16::restart()
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{
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_started = true;
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_crc = _startMask;
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_count = 0;
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}
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void CRC16::add(uint8_t value)
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{
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_count++;
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if (_canYield && ((_count & 0xFF) == 0)) yield();
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_update(value);
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}
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void CRC16::add(const uint8_t * array, uint16_t length)
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{
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while (length--)
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{
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add(*array++);
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}
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}
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uint16_t CRC16::getCRC()
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{
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uint16_t rv = _crc;
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if (_reverseOut) rv = _reverse(rv);
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rv ^= _endMask;
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return rv;
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}
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void CRC16::_update(uint8_t value)
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{
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if (!_started) restart();
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if (_reverseIn) value = _reverse8(value);
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_crc ^= ((uint16_t)value) << 8;
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for (uint8_t i = 8; i; i--)
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{
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if (_crc & (1UL << 15))
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{
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_crc <<= 1;
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_crc ^= _polynome;
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}
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else
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{
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_crc <<= 1;
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}
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}
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}
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uint16_t CRC16::_reverse(uint16_t in)
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{
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uint16_t x = in;
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x = (((x & 0XAAAA) >> 1) | ((x & 0X5555) << 1));
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x = (((x & 0xCCCC) >> 2) | ((x & 0X3333) << 2));
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x = (((x & 0xF0F0) >> 4) | ((x & 0X0F0F) << 4));
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x = (( x >> 8) | (x << 8));
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return x;
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}
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uint8_t CRC16::_reverse8(uint8_t in)
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{
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uint8_t x = in;
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x = (((x & 0xAA) >> 1) | ((x & 0x55) << 1));
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x = (((x & 0xCC) >> 2) | ((x & 0x33) << 2));
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x = ((x >> 4) | (x << 4));
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return x;
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}
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// -- END OF FILE --
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