使用485通讯协议驱动变频器

uint16转化为uint8类型为什么会造成数据截断

在计算机科学中，uint16类型通常表示一个16位的无符号整数，而uint8类型则表示一个8位无符号整数。当把一个uint16类型的变量转换为uint8类型的变量时，会发生数据截断。

因为uint8类型只能容纳8位的二进制数据，而uint16类型却有16位的二进制数据，因此在将uint16转换为uint8类型时，原数据的高8位数据会被截断丢弃，只保留低8位数据。这就是数据截断的原因。

例如，如果一个uint16类型的变量值为1000000000000011，以二进制表示为0b00000000 10000000 00000011，如果将其转换为uint8类型，只保留低8位，即0b00000011就会丢失高8位0b00000000 10000000。这就造成了数据截断。

因此，在进行变量类型转换时，程序员需要注意数据范围及目标数据类型能够容纳的数据范围，避免数据截断造成程序出错。

因此组合数据的时候RPMSend会&0XFF00>>8，将原先高八位的数据右移到低8位，强转位uinit8_t,保留了低8位的数据。

组合接收的数据：

uint16_t  DCCompressor.LineCurren;

       DCCompressor.LineCurrent = (uint16_t)((CompRecvBuff[27]<<8)+CompRecvBuff[28])

驱动函数：

void SendToCompDriver(uint16_t RPMSend, uint8_t type)

{

       static uint8_t task=0;

       uint16_t crcData;

       uint8_t   Send;

      

//    if(DCCompressor.CommIndex>=60)

//           Systemalarm.DCCompCommAlarm=1;

//    else

//           Systemalarm.DCCompCommAlarm=0;

      

       if(DCCompressor.CommIndex<60)

       {

              DCCompressor.CommIndex++;

              Systemalarm.DCCompCommAlarm=0;

       }

       else

              Systemalarm.DCCompCommAlarm=1;

       switch(task)

       {

              case 0://set compressor speed

                    

                     task++;

                     break;

              case 1:

                     if(RPMSend>0)

                     {

                            Send = 0x01;

                     }

                     else

                     {

                            Send = 0x00;

                     }

                     CompSendBuff[0] =0x01;

                     CompSendBuff[1] =0x10;

                     CompSendBuff[2] =0x19;

                     CompSendBuff[3] =0x02;

                     CompSendBuff[4] =0x00;

                     CompSendBuff[5] =0x02;

                     CompSendBuff[6] =0x04;

                     CompSendBuff[7] =0x00;

                     CompSendBuff[8] =Send;

                     CompSendBuff[9] =(uint8_t)(((RPMSend/6)&0xFF00)>>8);

                     CompSendBuff[10] =(uint8_t)((RPMSend/6)&0x00FF);

                     crcData = crc16(CompSendBuff, 11);

                     CompSendBuff[11] =(uint8_t)((crcData>>8)&0x00FF);

                     CompSendBuff[12] =(uint8_t)(crcData&0x00FF);

                     CompSendCount=13;

                     beginCompSend();

                     task++;

                     break;

              case 2:

                    

                     task++;

                     break;

              case 3://Read drive data

                     CompSendBuff[0] =0x01;

                     CompSendBuff[1] =0x03;

                     CompSendBuff[2] =0x15;

                     CompSendBuff[3] =0x1E;

                     CompSendBuff[4] =0x00;

                     CompSendBuff[5] =0x17;

                     crcData = crc16(CompSendBuff, 6);

                     CompSendBuff[6] =(uint8_t)((crcData>>8)&0x00FF);

                     CompSendBuff[7] =(uint8_t)(crcData&0x00FF);

                     CompSendCount=8;

                     beginCompSend();

                     task=0;

                     break;

              default:

                     task=0;

                     break;

       }

}