## how to convert binary data to float value?

Hello all, For my data logger project I'm logging data to a SD card. Here I'm storing the data in binary format. I'm logging accelerometer and temp&humidity sensors. I could read data byte by byte. Hence to print ADXL data (two bytes), I combine each two byte data. Hence four bytes has to be combined to get temparature data. Unfortunately for temparature I failed to print actual data. There is some conversion problem. I'm looking some help regarding how to convert data to floats.

Code to read and print binary to uint16_t ( accelerometer data): working

``` while ((nr = fgetc(logFile)) != EOF){
pc.printf(" \r\n %d ",nr);
acc_con[i] = nr;
if (i == 1){
acc = (acc_con[1]<<8) | acc_con[0];
pc.printf(" \r\n %i ",acc);
i = 0;}
else i++;
}
```

Code to read and print binary to float ( temparature data): Not working

```while ((nr = fgetc(logFile)) != EOF){
pc.printf(" \r\n %d ",nr);
humicon[i] = nr;
if (i == 3){
hum = (humicon[0] << 24) | (humicon[1] << 16) | (humicon[2] << 8) | humicon[3];
pc.printf(" \r\n %f ",hum);
i = 0;}
else i++;
}
```

The byte by byte raw data from variable nr is: 24, 58, 46, 66, and the output from variable hum is: 406466112.000000

How did you write humicon in the first place? And what is the format you read it from your device like?

posted by Erik Olieman 13 Dec 2016

I don't know much about formats. I get the correct output with below code.

```int main() {

int nr;
FILE *fp = fopen("/sd/PCE000.bin", "rb");
fclose(fp);
}
```

I would like to know the formula for the conversion. Thank you.

posted by Mohan gandhi Vinnakota 14 Dec 2016

It is working. It is little endien byte order.

```while ((nr = fgetc(logFile)) !=EOF){
humicon[i] = nr;
if (i == 3){
float x;
const unsigned char bytes[] = {humicon[0],humicon[1],humicon[2],humicon[3]};
memcpy(&x, bytes, sizeof x);
pc.printf("%f\n", x);
i = 0;}
else i++;
}
```
posted by Mohan gandhi Vinnakota 14 Dec 2016
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