函数
1 //四个字节转换成folat型 2 float FourBytesToFloat (UCHAR byte1,UCHAR byte2,UCHAR byte3,UCHAR byte4) 3 { 4 int bits=( byte1 << 24 ) + ( byte2 << 16 ) + ( byte3 << 8) + byte4; 5 int s = ( bits >> 31 ) == 0 ? 1 : -1; 6 int e = ( bits >> 23 ) & 0xff; 7 int m = ( e == 0 ) ? 8 ( bits & 0x7fffff ) << 1 : 9 ( bits & 0x7fffff ) | 0x800000; 10 return s * m * ( float ) pow( 2, e - 150 ); 11 }
调用
CString strTemp; strTemp = strRecv.Right(2); BYTE b1 = strtol(strTemp, NULL, 16); strTemp = strRecv.Mid(strRecv.GetLength() - 4, 2); BYTE b2 = strtol(strTemp, NULL, 16); strTemp = strRecv.Mid(strRecv.GetLength() - 6, 2); BYTE b3 = strtol(strTemp, NULL, 16); strTemp = strRecv.Mid(strRecv.GetLength() - 8, 2); BYTE b4 = strtol(strTemp, NULL, 16); float fValue = (FourBytesToFloat(b4, b3, b2, b1));
方法2：
函数
1 float Bit4ToFloat(int a, int b, int c, int d) 2 { 3 float freq; 4 unsigned char test[4] = { a, b, c, d }; //输入的数据，高字节到低字节排列 5 unsigned char* Modbus_HoldReg[1000]; //保持寄存器指针，一个字节 6 7 //第一步：指针首先指向地址 8 Modbus_HoldReg[20] = ((unsigned char*)(&freq)) + 3; //低地址指向高位 9 Modbus_HoldReg[21] = ((unsigned char*)(&freq)) + 2; 10 Modbus_HoldReg[22] = ((unsigned char*)(&freq)) + 1; 11 Modbus_HoldReg[23] = ((unsigned char*)(&freq)) + 0; //高地址指向低位 12 13 //第二步：将数据映射到指定地址 14 *Modbus_HoldReg[20] = test[0]; 15 *Modbus_HoldReg[21] = test[1]; 16 *Modbus_HoldReg[22] = test[2]; 17 *Modbus_HoldReg[23] = test[3]; 18 19 return freq; 20 }
调用
float ff = Bit4ToFloat(0x43, 0x6B, 0x5A, 0x2F);//结果235.352280