/***************************Lcd1602.c文件程序源代码*****************************/
（此处省略，可参考之前章节的代码）
/****************************RS485.c文件程序源代码*****************************/
（此处省略，可参考之前章节的代码）
/****************************CRC16.c文件程序源代码****************************/
/* CRC16计算函数，ptr-数据指针，len-数据长度，返回值-计算出的CRC16数值 */
unsigned int GetCRC16(unsigned char *ptr, unsigned char len)
{
unsigned int index;
unsigned char crch = 0xFF; //高CRC字节
unsigned char crcl = 0xFF; //低CRC字节
unsigned char code TabH[] = { //CRC高位字节值表
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 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, 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, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 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,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 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, 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
} ;
unsigned char code TabL[] = { //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
sbit BUZZ = P1^6;
bit flagBuzzOn = 0; //蜂鸣器启动标志
unsigned char T0RH = 0; //T0重载值的高字节
unsigned char T0RL = 0; //T0重载值的低字节
unsigned char regGroup[5]; //Modbus寄存器组，地址为0x00～0x04
void ConfigTimer0(unsigned int ms);
extern void UartDriver();
extern void ConfigUART(unsigned int baud);
extern void UartRxMonitor(unsigned char ms);
extern void UartWrite(unsigned char *buf, unsigned char len);
extern unsigned int GetCRC16(unsigned char *ptr, unsigned char len);
extern void InitLcd1602();
extern void LcdShowStr(unsigned char x, unsigned char y, unsigned char *str);
void main()
{
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 */
void UartAction(unsigned char *buf, unsigned char len)
{
unsigned char i;
unsigned char cnt;
unsigned char str[4];
unsigned int crc;
unsigned char crch, crcl;
if (buf[0] != 0x01) // 本机从地址设定为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])
{
case 0x03: //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) // 01 03 [ 00 i ] [ xx cnt ] [ crch crcl ]
{
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02-无效地址
len = 3;
break;
}
case 0x06: //写入单个寄存器
if ((buf[2]==0x00) && (buf[3]<=0x05)) //只支持0x0000～0x0005
{
if (buf[3] <= 0x04) // 01 06 [ 00 i ] [ xx regG ] [ crch crcl ]
{
i = buf[3]; //提取寄存器地址
regGroup = buf[5]; //保存寄存器数据
cnt = regGroup >> 4; //显示到液晶上 16进制转string
if (cnt >= 0xA)
str[0] = cnt - 0xA + 'A';
else
str[0] = cnt + '0';
cnt = regGroup & 0x0F;
if (cnt >= 0xA)
str[1] = cnt - 0xA + 'A';
else
str[1] = cnt + '0';
str[2] = '';
LcdShowStr(i*3, 0, str);
}
else //地址0x05为蜂鸣器状态 // 01 06 [ 00 05 ] [ xx on ] [ crch crcl ]
{
flagBuzzOn = (bit)buf[5]; //寄存器值转为蜂鸣器的开关
}
len -= 2; //长度-2以重新计算CRC并返回原帧
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