x80,0x41,0x00,0xC1,0x81,0x40,0x01,0xC0,
0x80,0x41,0x00,0xC1,0x81,0x40,0x00,0xC1,0x81,0x40,
0x01,0xC0,0x80,0x41,0x01,0xC0,0x80,0x41,0x00,0xC1,
0x81,0x40,0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,
0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x01,0xC0,
0x80,0x41,0x00,0xC1,0x81,0x40
};
unsignedcharcodeTabL[]={//CRC低位字节值表
0x00,0xC0,0xC1,0x01,0xC3,0x03,0x02,0xC2,0xC6,0x06,
0x07,0xC7,0x05,0xC5,0xC4,0x04,0xCC,0x0C,0x0D,0xCD,
0x0F,0xCF,0xCE,0x0E,0x0A,0xCA,0xCB,0x0B,0xC9,0x09,
0x08,0xC8,0xD8,0x18,0x19,0xD9,0x1B,0xDB,0xDA,0x1A,
0x1E,0xDE,0xDF,0x1F,0xDD,0x1D,0x1C,0xDC,0x14,0xD4,
0xD5,0x15,0xD7,0x17,0x16,0xD6,0xD2,0x12,0x13,0xD3,
0x11,0xD1,0xD0,0x10,0xF0,0x30,0x31,0xF1,0x33,0xF3,
0xF2,0x32,0x36,0xF6,0xF7,0x37,0xF5,0x35,0x34,0xF4,
0x3C,0xFC,0xFD,0x3D,0xFF,0x3F,0x3E,0xFE,0xFA,0x3A,
0x3B,0xFB,0x39,0xF9,0xF8,0x38,0x28,0xE8,0xE9,0x29,
0xEB,0x2B,0x2A,0xEA,0xEE,0x2E,0x2F,0xEF,0x2D,0xED,
0xEC,0x2C,0xE4,0x24,0x25,0xE5,0x27,0xE7,0xE6,0x26,
0x22,0xE2,0xE3,0x23,0xE1,0x21,0x20,0xE0,0xA0,0x60,
0x61,0xA1,0x63,0xA3,0xA2,0x62,0x66,0xA6,0xA7,0x67,
0xA5,0x65,0x64,0xA4,0x6C,0xAC,0xAD,0x6D,0xAF,0x6F,
0x6E,0xAE,0xAA,0x6A,0x6B,0xAB,0x69,0xA9,0xA8,0x68,
0x78,0xB8,0xB9,0x79,0xBB,0x7B,0x7A,0xBA,0xBE,0x7E,
0x7F,0xBF,0x7D,0xBD,0xBC,0x7C,0xB4,0x74,0x75,0xB5,
0x77,0xB7,0xB6,0x76,0x72,0xB2,0xB3,0x73,0xB1,0x71,
0x70,0xB0,0x50,0x90,0x91,0x51,0x93,0x53,0x52,0x92,
0x96,0x56,0x57,0x97,0x55,0x95,0x94,0x54,0x9C,0x5C,
0x5D,0x9D,0x5F,0x9F,0x9E,0x5E,0x5A,0x9A,0x9B,0x5B,
0x99,0x59,0x58,0x98,0x88,0x48,0x49,0x89,0x4B,0x8B,
0x8A,0x4A,0x4E,0x8E,0x8F,0x4F,0x8D,0x4D,0x4C,0x8C,
0x44,0x84,0x85,0x45,0x87,0x47,0x46,0x86,0x82,0x42,
0x43,0x83,0x41,0x81,0x80,0x40
};
while(len--)//计算指定长度的CRC
{
index=crch^*ptr++;
crch=crcl^TabH[index];
crcl=TabL[index];
}
return((crch<8)|crcl);
}
关于CRC校验的算法，如果不是专门学习校验算法本身，大家可以不去研究这个程序的细节，直接使用现成的函数即可。
/*main.c文件程序源代码/
#include
sbitBUZZ=P1^6;
bitflagBuzzOn=0;//蜂鸣器启动标志
unsignedcharT0RH=0;//T0重载值的高字节
unsignedcharT0RL=0;//T0重载值的低字节
unsignedcharregGroup[5];//Modbus寄存器组，地址为0x00～0x04
voidConfigTimer0(unsignedintms);
externvoidUartDriver();
externvoidConfigUART(unsignedintbaud);
externvoidUartRxMonitor(unsignedcharms);
externvoidUartWrite(unsignedchar*buf,unsignedcharlen);
externunsignedintGetCRC16(unsignedchar*ptr,unsignedcharlen);
externvoidInitLcd1602();
externvoidLcdShowStr(unsignedcharx,unsignedchary,unsignedchar*str);
voidmain()
{
EA=1;//开总中断
ConfigTimer0(1);//配置T0定时1ms
ConfigUART(9600);//配置波特率为9600
InitLcd1602();//初始化液晶
while(1)
{
UartDriver();//调用串口驱动
}
}
/*串口动作函数，根据接收到的命令帧执行响应的动作
buf-接收到的命令帧指针，len-命令帧长度*/
voidUartAction(unsignedchar*buf,unsignedcharlen)
{
unsignedchari;
unsignedcharcnt;
unsignedcharstr[4];
unsignedintcrc;
unsignedcharcrch,crcl;
if(buf[0]!=0x01)//本例中的本机地址设定为0x01，
{//如数据帧中的地址字节与本机地址不符，
return;//则直接退出，即丢弃本帧数据不做任何处理
}
//地址相符时，再对本帧数据进行校验
crc=GetCRC16(buf,len-2);//计算CRC校验值
crch=crc>>8;
crcl=crc&0xFF;
if((buf[len-2]!=crch)||(buf[len-1]!=crcl))
{
return;//如CRC校验不符时直接退出
}
//地址和校验字均相符后，解析功能码，执行相关操作
switch(buf[1])
{
case0x03://读取一个或连续的寄存器
if((buf[2]==0x00)&&(buf[3]<=0x05))//只支持0x0000～0x0005
{
if(buf[3]<=0x04)
{
i=buf[3];//提取寄存器地址
cnt=buf[5];//提取待读取的寄存器数量
buf[2]=cnt*2;//读取数据的字节数，为寄存器数*2
len=3;//帧前部已有地址、功能码、字节数共3个字节
while(cnt--)
{
buf[len++]=0x00;//寄存器高字节补0
buf[len++]=regGroup[i++];//寄存器低字节
}
}
else//地址0x05为蜂鸣器状态
{
buf[2]=2;//读取数据的字节数
buf[3]=0x00;
buf[4]=flagBuzzOn;
len=5;
}
break;
}
else//寄存器地址不被支持时，返回错误码
{
buf[1]=0x83;//功能码最高位置1
buf[2]=0x02;//设置异常码为0
|
