storing float value to unsigned char array

Question

Sorry to ask this but I have searched for this small thing and found somthing related on this below link but was unable get any idea

How to store a float value suppose 0.00895 to an unsigned char which is later used to store in the memory buffer.

And later I need to read the array back and want to read it back from the memory.

Thanks

Why do you need (want) to store float value in unsigned char array? You can use float value. In every case it is holded in memory as chunk of bytes. — George Gaál
– George Gaál, Commented Nov 12, 2012 at 22:19
because my buffer function for storing data into memory takes its parameter as an unsigned char.I didnt get you abt float value ? — user1016528
– user1016528, Commented Nov 12, 2012 at 23:08

paddy · Accepted Answer · 2012-11-12 23:18:27Z

6

You don't need memcpy for this... That would be useful if you were copying a float array into a buffer elsewhere in memory. All you really need is to use a different pointer type to look into the character array.

const size_t BUFSIZE = 4096;
char buffer[BUFSIZE];
float *f_buf = (float*)buffer;

If all you wanted was to stick a single float into the start of the buffer, either of the following two lines is okay:

*f_buf = 0.00895;

f_buf[0] = 0.00895;

All it's really doing is letting you see the buffer as an array of floats.

int i;

/* Put a bunch of floats into the buffer */
for( i = 0; i < 10; i++ ) {
    f_buf[i] = i / 2;
}

/* Display contents of buffer in hex */
for( i = 0; i < 10 * sizeof(float); i++ ) {
    printf( "%02x", (int)buffer[i] );
}
printf( "\n" );

/* Sanity-test the buffer contents */
for( i = 0; i < 10; i++ ) {
    printf( "%d: %f\n", i, f_buf[i] );
}

answered Nov 12, 2012 at 23:18

paddy

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6 Comments

user1016528 Over a year ago

yes this looks to be what I'm searching for but I want to store the float value in an unsigned char.

paddy Over a year ago

You mean an array of unsigned char, right? In that case use unsigned char instead of char in my example. It makes no difference. If you mean a single unsigned char, you are dreaming. A float occupies four bytes, while a char occupies only one.

user1016528 Over a year ago

when Im trying to test buffer contents like this

*f_buf = 0.00895; check =buffer[0];							sprintf(value_current,"%f",check);							position =0x40; Lcd_move(position); Lcd_puts (value_current);

the output is 152 but the buffer actually contains 0.00895.what is this value?

user1016528 Over a year ago

I think this is not wrkng const size_t BUFSIZE = 4096; char buffer[BUFSIZE]; float *f_buf = (float*)buffer;

Motorhead Over a year ago

In the hex dump, I would expect to see 80 characters (2 hex digits for each byte), but instead I see a lot more. Eg here's what I get when i run it on my machine (where a float is 4 bytes) Any idea why?:00000000000000000000ffffff803f0000ffffff803f000000400000004000004040000040400000ffffff80400000ffffff8040

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dzada · Accepted Answer · 2012-11-12 22:15:01Z

3

you can copy the memory of the float into the char buffer.

float a;
char buffer[sizeof(float)];
memcpy(buffer,&a,sizeof(float));

answered Nov 12, 2012 at 22:15

dzada

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1 Comment

user1016528 Over a year ago

Can I use sprintf(value_current,"%d",buffer[0]); to see my output in the buffer 0th element.Can I be able to see the data of the buffer.

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