// // FILE: CRC16.cpp // AUTHOR: Rob Tillaart // PURPOSE: Arduino class for CRC16 // URL: https://github.com/RobTillaart/CRC #include "CRC16.h" CRC16::CRC16() { reset(); } void CRC16::reset() { _polynome = CRC16_DEFAULT_POLYNOME; _startMask = 0; _endMask = 0; _crc = 0; _reverseIn = false; _reverseOut = false; _started = false; _count = 0; } void CRC16::restart() { _started = true; _crc = _startMask; _count = 0; } void CRC16::add(uint8_t value) { _count++; _update(value); } void CRC16::add(uint8_t * array, uint32_t length) { _count += length; while (length--) { yield(); uint8_t data = *array++; _update(data); } } uint16_t CRC16::getCRC() { uint16_t rv = _crc; if (_reverseOut) rv = _reverse(rv); rv ^= _endMask; return rv; } void CRC16::_update(uint8_t value) { if (!_started) restart(); if (_reverseIn) value = _reverse8(value); _crc ^= ((uint16_t)value) << 8;; for (uint8_t i = 8; i; i--) { if (_crc & (1UL << 15)) { _crc <<= 1; _crc ^= _polynome; } else { _crc <<= 1; } } } uint16_t CRC16::_reverse(uint16_t in) { uint16_t x = in; x = (((x & 0XAAAA) >> 1) | ((x & 0X5555) << 1)); x = (((x & 0xCCCC) >> 2) | ((x & 0X3333) << 2)); x = (((x & 0xF0F0) >> 4) | ((x & 0X0F0F) << 4)); x = (( x >> 8) | (x << 8)); return x; } uint8_t CRC16::_reverse8(uint8_t in) { uint8_t x = in; x = (((x & 0xAA) >> 1) | ((x & 0x55) << 1)); x = (((x & 0xCC) >> 2) | ((x & 0x33) << 2)); x = ((x >> 4) | (x << 4)); return x; } // -- END OF FILE --