最近用到modbus校验,就顺便用之前写的方法重编辑了一下modbus的校验。
2种计算方法:
查表法(需要提前生成表格),直接计算法(需要先计算出表格再进行查表);
初值计算就不写了:参考
预定义参数:
#ifdef _X86_
typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
typedef unsigned int uint32_t;
typedef unsigned char byte;
typedef char int8_t;
typedef short int16_t;
typedef int int32_t;
typedef unsigned char u8;
typedef unsigned char byte;
typedef unsigned short u16;
typedef unsigned int u32;
# ifdef BOOL
# undef BOOL
# endif
typedef int BOOL;
typedef char s8;
typedef short s16;
typedef int s32;
#else
typedef unsigned char u8;
typedef unsigned char byte;
typedef unsigned short u16;
typedef unsigned int u32;
typedef int BOOL;
typedef char s8;
typedef short s16;
typedef int s32;
#endif
#define getarraylen(array) (int)(sizeof(array) / sizeof(array[0]))
#define unsed(A) \
do { \
(void)(A); \
} while (0)
#define uSucess (0)
#define uError (1)
#define uNotFound (2)
#define true 1
#define false 0
表格生成算法:
static uint16_t modbusTable[256];
//位逆转
static uint16_t bitrev(uint16_t input, int bw) {
int i;
uint16_t var;
var = 0;
for (i = 0; i < bw; i++) {
if (input & 0x01) {
var |= 1 << (bw - 1 - i);
}
input >>= 1;
}
return var;
}
void crc16_init(uint16_t poly) {
int i;
int j;
uint16_t c;
poly = bitrev(poly, 16) & 0xFFFF;
for (i = 0; i < 256; i++) {
c = i;
for (j = 0; j < 8; j++) {
c = (c & 1) ? (poly ^ (c >> 1)) : (c >> 1);
}
modbusTable[i] = c;
if ((i + 1) % 8 == 0) {
printf(" 0x%04x\n", c);
} else {
printf(" 0x%04x", c);
}
}
}
查表返回校验结果:
uint16_t modbusCrc(void* input, uint16_t len) {
int i;
uint8_t index;
uint8_t* p;
uint16_t crc = 0xFFFF;
p = (uint8_t*)input;
#ifndef checkTable
crc16_init(0x8005);
#endif
for (i = 0; i < len; i++) {
index = (*p ^ crc);
crc = (crc >> 8) ^ modbusTable[index];
p++;
}
return crc & 0xFFFF;
}
完整代码如下:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef _X86_
typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
typedef unsigned int uint32_t;
typedef unsigned char byte;
typedef char int8_t;
typedef short int16_t;
typedef int int32_t;
typedef unsigned char u8;
typedef unsigned char byte;
typedef unsigned short u16;
typedef unsigned int u32;
# ifdef BOOL
# undef BOOL
# endif
typedef int BOOL;
typedef char s8;
typedef short s16;
typedef int s32;
#else
typedef unsigned char u8;
typedef unsigned char byte;
typedef unsigned short u16;
typedef unsigned int u32;
typedef int BOOL;
typedef char s8;
typedef short s16;
typedef int s32;
#endif
#define getarraylen(array) (int)(sizeof(array) / sizeof(array[0]))
#define unsed(A) \
do { \
(void)(A); \
} while (0)
#define uSucess (0)
#define uError (1)
#define uNotFound (2)
#define true 1
#define false 0
//#define checkTable
#ifdef checkTable
uint16_t modbusTable[] = {
0x0000, 0xc0c1, 0xc181, 0x0140, 0xc301, 0x03c0, 0x0280, 0xc241, 0xc601, 0x06c0, 0x0780, 0xc741, 0x0500, 0xc5c1,
0xc481, 0x0440, 0xcc01, 0x0cc0, 0x0d80, 0xcd41, 0x0f00, 0xcfc1, 0xce81, 0x0e40, 0x0a00, 0xcac1, 0xcb81, 0x0b40,
0xc901, 0x09c0, 0x0880, 0xc841, 0xd801, 0x18c0, 0x1980, 0xd941, 0x1b00, 0xdbc1, 0xda81, 0x1a40, 0x1e00, 0xdec1,
0xdf81, 0x1f40, 0xdd01, 0x1dc0, 0x1c80, 0xdc41, 0x1400, 0xd4c1, 0xd581, 0x1540, 0xd701, 0x17c0, 0x1680, 0xd641,
0xd201, 0x12c0, 0x1380, 0xd341, 0x1100, 0xd1c1, 0xd081, 0x1040, 0xf001, 0x30c0, 0x3180, 0xf141, 0x3300, 0xf3c1,
0xf281, 0x3240, 0x3600, 0xf6c1, 0xf781, 0x3740, 0xf501, 0x35c0, 0x3480, 0xf441, 0x3c00, 0xfcc1, 0xfd81, 0x3d40,
0xff01, 0x3fc0, 0x3e80, 0xfe41, 0xfa01, 0x3ac0, 0x3b80, 0xfb41, 0x3900, 0xf9c1, 0xf881, 0x3840, 0x2800, 0xe8c1,
0xe981, 0x2940, 0xeb01, 0x2bc0, 0x2a80, 0xea41, 0xee01, 0x2ec0, 0x2f80, 0xef41, 0x2d00, 0xedc1, 0xec81, 0x2c40,
0xe401, 0x24c0, 0x2580, 0xe541, 0x2700, 0xe7c1, 0xe681, 0x2640, 0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0,
0x2080, 0xe041, 0xa001, 0x60c0, 0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281, 0x6240, 0x6600, 0xa6c1, 0xa781, 0x6740,
0xa501, 0x65c0, 0x6480, 0xa441, 0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaf01, 0x6fc0, 0x6e80, 0xae41, 0xaa01, 0x6ac0,
0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840, 0x7800, 0xb8c1, 0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41,
0xbe01, 0x7ec0, 0x7f80, 0xbf41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40, 0xb401, 0x74c0, 0x7580, 0xb541, 0x7700, 0xb7c1,
0xb681, 0x7640, 0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101, 0x71c0, 0x7080, 0xb041, 0x5000, 0x90c1, 0x9181, 0x5140,
0x9301, 0x53c0, 0x5280, 0x9241, 0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481, 0x5440, 0x9c01, 0x5cc0,
0x5d80, 0x9d41, 0x5f00, 0x9fc1, 0x9e81, 0x5e40, 0x5a00, 0x9ac1, 0x9b81, 0x5b40, 0x9901, 0x59c0, 0x5880, 0x9841,
0x8801, 0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1, 0x8a81, 0x4a40, 0x4e00, 0x8ec1, 0x8f81, 0x4f40, 0x8d01, 0x4dc0,
0x4c80, 0x8c41, 0x4400, 0x84c1, 0x8581, 0x4540, 0x8701, 0x47c0, 0x4680, 0x8641, 0x8201, 0x42c0, 0x4380, 0x8341,
0x4100, 0x81c1, 0x8081, 0x4040};
#else
static uint16_t modbusTable[256];
//位逆转
static uint16_t bitrev(uint16_t input, int bw) {
int i;
uint16_t var;
var = 0;
for (i = 0; i < bw; i++) {
if (input & 0x01) {
var |= 1 << (bw - 1 - i);
}
input >>= 1;
}
return var;
}
void crc16_init(uint16_t poly) {
int i;
int j;
uint16_t c;
poly = bitrev(poly, 16) & 0xFFFF;
for (i = 0; i < 256; i++) {
c = i;
for (j = 0; j < 8; j++) {
c = (c & 1) ? (poly ^ (c >> 1)) : (c >> 1);
}
modbusTable[i] = c;
if ((i + 1) % 8 == 0) {
printf(" 0x%04x\n", c);
} else {
printf(" 0x%04x", c);
}
}
}
#endif
uint16_t modbusCrc(void* input, uint16_t len) {
int i;
uint8_t index;
uint8_t* p;
uint16_t crc = 0xFFFF;
p = (uint8_t*)input;
#ifndef checkTable
crc16_init(0x8005);
#endif
for (i = 0; i < len; i++) {
index = (*p ^ crc);
crc = (crc >> 8) ^ modbusTable[index];
p++;
}
return crc & 0xFFFF;
}
int main() {
u16 crc = 0;
byte data[] = {0x05, 0x07, 0x05, 0x07, 0x05, 0x07, 0x05, 0x07, 0x05, 0x07};
crc = modbusCrc(data, getarraylen(data));
printf("CRC16_1 = 0x%02X\n", crc);
return 0;
}
执行结果如下:
1. 直接生成表 计算:
//#define checkTable
2. 查表法: