C 语言在线 http://codepad.org

校验和计算：

 

#include <stdio.h>
#define u8     unsigned char
#define u16     unsigned int

unsigned char CalculateChecksum(const u8 *pData, u16 Length)
{
    u8 byChecksum = 0xff;
    u16 i;
    for (i = 0; i<Length; i++)
        byChecksum ^= *(pData+i);
    return byChecksum;
}

void main()
{
unsigned char checksum;
unsigned char aa[]={0x04, 0x00, 0x1E, 0x20};
checksum = CalculateChecksum(aa,4);
printf("%x",checksum );
  
}