25 lines
657 B
C
25 lines
657 B
C
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#include "basic.h"
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// Calculate the CRC for transmitted and received data using
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// the CCITT 16bit algorithm (X^16 + X^12 + X^5 + 1).
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uint16_t crc16(char * buf, int len){
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unsigned int crc=0xffff;
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for(int i=0;i<len;i++){
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crc = (unsigned char)(crc >> 8) | (crc << 8);
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crc ^= buf[i];
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crc ^= (unsigned char)(crc & 0xff) >> 4;
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crc ^= (crc << 8) << 4;
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crc ^= ((crc & 0xff) << 4) << 1;
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};
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return crc;
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};
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/* Note:
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It is best not to alter this code. For example, (crc<<8)<<4 does
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not generate the same code as crc<<12. Although the result of the
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computation is the same, the latter generates much more code and
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executes slower.
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*/
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