modbus通信小程序.txt

modbus通信小程序

//通信程序中CRC校验函数是核心，其他根据需要修改。程序通过了验证。
#include "iom16v.h"
unsigned int crc=0xffff;     
unsigned char data[]={0x05,0x03,0x02,0x04,0x02};
/*串口初始化函数*/
void Uart_Init(void)
{
UCSRA = 0x02; /*倍速*/ 
UCSRB = 0x18; /*允许接收和发送*/
UCSRC = 0x06; /*8位数据*/ 
UBRRH = 0x00; UBRRL = 12; /*9600*/
}

void delay(unsigned int ms)//延时
{
    unsigned int i,j;
for(i=0;i<ms;i++)
    {
    for(j=0;j<1142;j++);
       }
}
/*数据发送，查询方式*/
void Uart_Transmit(unsigned char i)
{
while (!(UCSRA & (1<<UDRE))); /* 等待发送缓冲器为空*/
UDR = i;    /* 发送数据*/
}
   
/*数据接收，查询方式*/
unsigned char Uart_Receive( void )
{
while (!(UCSRA & (1<<RXC))); /* 等待接收数据*/ 
return UDR;            /* 获取并返回数据*/
}
//================================
//===============CRC校验函数
//=================================
unsigned int cal_crc(unsigned char *ptr, unsigned int len) 
{   
     unsigned int crc=0xffff;   
     unsigned char i;   
     while(len!=0) 
   {   
      crc^=*ptr; 
      for(i=0;i<8;i++) 
      {   
        if((crc&0x0001)==0)
   crc=crc>>1; 
         else 
            { 
              crc=crc>>1; 
              crc^=0xa001; 
            }                     
      } 
         len-=1; 
          ptr++; 
   }   
     return crc; 

}   

/*主函数*/
void main(void)
{
unsigned int AddNum=0;
DDRA = 0x00;    /*方向输入*/ 
PORTA =0xFF;   /*打开上拉*/ 
DDRB = 0xFF;    /*方向输出*/ 
PORTB = 0xFF;    /*电平设置*/ 
DDRC = 0x00;
PORTC = 0xFF; 
DDRD = 0x02; 
PORTD = 0xFF; 
Uart_Init(); 

while(1) 
{ 

Uart_Transmit(data[0]);
Uart_Transmit(data[1]);
Uart_Transmit(data[2]);

AddNum++;
data[3]=AddNum/10;
data[4]=(AddNum%10)*10;

if(AddNum==50)
{
   AddNum=0; 
}

//修改下列值来确定
Uart_Transmit(data[3]);
Uart_Transmit(data[4]);

crc=cal_crc(data,5);
Uart_Transmit(crc);   //低字节
Uart_Transmit(crc>>8);//高字节
delay(400);//延时

}