44 lines
1.1 KiB
C
44 lines
1.1 KiB
C
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#include "utils.h"
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/*
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生成多项式 (x^16 + x^15 + x^2 + 1）
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*/
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uint16_t modbus_crc16(uint8_t* data, int length)
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{
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uint16_t crc = 0xFFFF; // 初始值FFFF
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uint16_t polynomial = 0x8005; // 多项式8005
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for (int i = 0; i < length; i++) {
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// 输入反转(REFIN)：对每个字节进行位反转
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uint8_t byte = data[i];
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uint8_t reversed_byte = 0;
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for (int j = 0; j < 8; j++) {
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reversed_byte = (reversed_byte << 1) | (byte & 0x01);
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byte >>= 1;
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}
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crc ^= (reversed_byte << 8); // 与高字节异或
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for (int j = 0; j < 8; j++) {
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if (crc & 0x8000) { // 检查最高位
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crc = (crc << 1) ^ polynomial;
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} else {
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crc <<= 1;
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}
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}
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}
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// 输出反转(REFOUT)：对16位CRC结果进行位反转
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uint16_t reversed_crc = 0;
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for (int i = 0; i < 16; i++) {
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reversed_crc = (reversed_crc << 1) | (crc & 0x0001);
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crc >>= 1;
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}
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// 结果异或值(XOROUT)：0000（实际不变）
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return reversed_crc ^ 0x0000;
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}
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