PLC通常将浮点数据类型直接以16进制数据的形式发送给上位机
上位机程序要进行数据的读取和发送，就需要进行浮点数据和16进制数据的转换
16进制转浮点
//16进制转浮点
float hex_2_float(unsigned char a,unsigned char b,unsigned char c,unsigned char d){
unsigned char pMem[4];
pMem[0] = d;
pMem[1] = c;
pMem[2] = b;
pMem[3] = a;
float *p = (float*)pMem;
return *p;
}
浮点转16进制
//浮点转16进制
unsigned long float_2_hex(float num){
union {
long int number;
float fnumber;
}A;
A.fnumber = num;
return A.number;
}
测试程序
// Example program
#include <stdio.h>
#include <string.h>
//16进制转浮点
float hex_2_float(unsigned char a,unsigned char b,unsigned char c,unsigned char d){
unsigned char pMem[4];
pMem[0] = d;
pMem[1] = c;
pMem[2] = b;
pMem[3] = a;
float *p = (float*)pMem;
return *p;
}
//浮点转16进制
unsigned long float_2_hex(float num){
union {
unsigned long number;
float fnumber;
}A;
A.fnumber = num;
return A.number;
}
int main()
{
printf("1.1f to hex: %08x\n",float_2_hex(1.10f));
printf("0x3f8ccccd to float: %.2f\n",hex_2_float(0x3f,0x8c,0xcc,0xcd));
return 0;
}
结果
对于16进制数据的收发，一定要格式化数据长度并且用0占空位。比如对于4字节数据0x3f，发送为00 00 00 3f而不是3f。