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102 lines
2.8 KiB
102 lines
2.8 KiB
#ifndef __HM_CRC_H
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#define __HM_CRC_H
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#define BITS_TO_BYTES(x) (((x)+7)>>3)
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#define BYTES_TO_BITS(x) ((x)<<3)
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extern uint16_t crc16_modbus(uint8_t *puchMsg, uint16_t usDataLen);
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extern uint8_t crc8(uint8_t *buf, const uint16_t bufLen);
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extern uint16_t crc16(uint8_t* buf, const uint16_t bufLen, const uint16_t startCRC, const uint16_t startBit, const uint16_t len_bits);
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//#define OUTPUT_DEBUG_INFO
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#define CRC8_INIT 0x00
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#define CRC8_POLY 0x01
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#define CRC16_MODBUS_POLYNOM 0xA001
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uint8_t crc8(uint8_t buf[], uint16_t len) {
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uint8_t crc = CRC8_INIT;
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for(uint8_t i = 0; i < len; i++) {
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crc ^= buf[i];
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for(uint8_t b = 0; b < 8; b ++) {
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crc = (crc << 1) ^ ((crc & 0x80) ? CRC8_POLY : 0x00);
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}
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}
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return crc;
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}
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uint16_t crc16_modbus(uint8_t buf[], uint16_t len) {
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uint16_t crc = 0xffff;
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uint8_t lsb;
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for(uint8_t i = 0; i < len; i++) {
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crc = crc ^ buf[i];
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for(int8_t b = 7; b >= 0; b--) {
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lsb = (crc & 0x0001);
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if(lsb == 0x01)
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crc--;
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crc = crc >> 1;
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if(lsb == 0x01)
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crc = crc ^ CRC16_MODBUS_POLYNOM;
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}
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}
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return crc;
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}
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// NRF24 CRC16 calculation with poly 0x1021 = (1) 0001 0000 0010 0001 = x^16+x^12+x^5+1
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uint16_t crc16(uint8_t *buf, const uint16_t bufLen, const uint16_t startCRC, const uint16_t startBit, const uint16_t len_bits)
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{
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uint16_t crc = startCRC;
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if ((len_bits > 0) && (len_bits <= BYTES_TO_BITS(bufLen)))
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{
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// The length of the data might not be a multiple of full bytes.
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// Therefore we proceed over the data bit-by-bit (like the NRF24 does) to
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// calculate the CRC.
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uint16_t data;
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uint8_t byte, shift;
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uint16_t bitoffs = startBit;
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// Get a new byte for the next 8 bits.
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byte = buf[bitoffs >> 3];
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#ifdef OUTPUT_DEBUG_INFO
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printf_P(PSTR("\nStart CRC %04X, %u bits:"), startCRC, len_bits);
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printf_P(PSTR("\nbyte %02X:"), byte);
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#endif
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while (bitoffs < len_bits + startBit)
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{
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shift = bitoffs & 7;
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// Shift the active bit to the position of bit 15
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data = ((uint16_t)byte) << (8 + shift);
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#ifdef OUTPUT_DEBUG_INFO
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printf_P(PSTR(" bit %u %u,"), shift, data & 0x8000 ? 1 : 0);
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#endif
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// Assure all other bits are 0
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data &= 0x8000;
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crc ^= data;
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if (crc & 0x8000)
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{
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crc = (crc << 1) ^ 0x1021; // 0x1021 = (1) 0001 0000 0010 0001 = x^16+x^12+x^5+1
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}
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else
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{
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crc = (crc << 1);
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}
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++bitoffs;
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if (0 == (bitoffs & 7))
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{
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// Get a new byte for the next 8 bits.
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byte = buf[bitoffs >> 3];
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#ifdef OUTPUT_DEBUG_INFO
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printf_P(PSTR("crc %04X:"), crc);
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if (bitoffs < len_bits + startBit)
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printf_P(PSTR("\nbyte %02X:"), byte);
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#endif
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}
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}
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}
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return crc;
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}
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#endif
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