B4J Question Convert HEX to Float

Philip Prins · Apr 25, 2017

Hello

I get a Hex string "3719" that i want to convert to Decimal 14105 .
How can i do this?

Tnx in advance
Philip

wonder · Apr 25, 2017

http://www.binaryhexconverter.com/hex-to-decimal-converter

Philip Prins · Apr 25, 2017

wonder said:
http://www.binaryhexconverter.com/hex-to-decimal-converter

View attachment 55117

Is there a function for this in B4J?

wonder · Apr 25, 2017

Once you write it, yes!

EDIT: There probably is, buried in some library...

EDIT2: My bad, of course there is!!! Bit.ParseInt() with radix 16.

EDIT3: Do you specifically need a 32-bit float value?

Jeffrey Cameron · Apr 25, 2017

@wonder is correct in the post above, Bit.ParseInt(...) would do what you are asking.

Also Look up the ByteConverter library: https://www.b4x.com/android/forum/threads/byteconverter-library.6787/

wonder · Apr 25, 2017

@Jeffrey Cameron, awesome!

wonder · Apr 25, 2017

I've actually wrote this C code two days ago... I can compile it

B4X:

#include <inttypes.h>

typedef unsigned char byte;

int64_t Int64FromHex(char* data)
{
    int64_t value;
    byte i, j, k;
    byte n = 7;
    for (i = 2; i < 17; i += 2)
    {
        j = i - 2;
        k = i - 1;
        byte a, b;
        if (data[j] >= '0' && data[j] <= '9')
        {
            a = data[j] - 48; // data[j] - '0'
        }
        else if (data[j] >= 'A' && data[j] <= 'F')
        {
            a = data[j] - 55; // data[j] - 'A' + 10
        }
        else if (data[j] >= 'a' && data[j] <= 'f')
        {
            a = data[j] - 87; // data[j] - 'a' + 10
        }
        else
        {
            a = 0;
        }
        if (data[k] >= '0' && data[k] <= '9')
        {
            b = data[k] - 48; // data[j] - '0'
        }
        else if (data[k] >= 'A' && data[k] <= 'F')
        {
            b = data[k] - 55; // data[j] - 'A' + 10
        }
        else if (data[k] >= 'a' && data[k] <= 'f')
        {
            b = data[k] - 87; // data[j] - 'a' + 10
        }
        else
        {
            b = 0;
        }
        ((char*)(&value))[n] = (a * 16) + b;
        --n;
    }
    return value;
}

Philip Prins · Apr 25, 2017

wonder said:
@Jeffrey Cameron, awesome!

I get the HEX from an arduino, it is a float converted to int
In C

B4X:

int16_t convertoFloatToInt16(float value, long max, long min) {
  float conversionFactor = (float) (INT16_t_MAX) / (float)(max - min);
  return (int16_t)(value * conversionFactor);
}

This is send and received as a Hex string ,max 4 characters like 5836.

I need to convert it back in a float like 21.37 .

I tried Byte converter BC.FloatsFromBytes(BC.HexToBytes(hex))(0) but the string is to short, should i add 0000?

wonder · Apr 25, 2017

I might be able to help you tomorrow...

Jeffrey Cameron · Apr 25, 2017

As @wonder said, the Bit.ParseInt("5836", 16) will give you an integer value for the hex string. You can then do whatever math you need to the integer value to convert it to your decimal value.

The byteconverter would be used if you needed each individual byte into any array (e.g. you needed "58" in one value and "36" in another value).

wonder · Apr 25, 2017

Not tested...

B4X:

#include <inttypes.h>

typedef unsigned char byte;

float FloatFromHex(char* data)
{
    float value;
    byte i, j, k;
    byte n = 3;
    for (i = 2; i < 9; i += 2)
    {
        j = i - 2;
        k = i - 1;
        byte a, b;
        if (data[j] >= '0' && data[j] <= '9')
        {
            a = data[j] - 48; // data[j] - '0'
        }
        else if (data[j] >= 'A' && data[j] <= 'F')
        {
            a = data[j] - 55; // data[j] - 'A' + 10
        }
        else if (data[j] >= 'a' && data[j] <= 'f')
        {
            a = data[j] - 87; // data[j] - 'a' + 10
        }
        else
        {
            a = 0;
        }
        if (data[k] >= '0' && data[k] <= '9')
        {
            b = data[k] - 48; // data[j] - '0'
        }
        else if (data[k] >= 'A' && data[k] <= 'F')
        {
            b = data[k] - 55; // data[j] - 'A' + 10
        }
        else if (data[k] >= 'a' && data[k] <= 'f')
        {
            b = data[k] - 87; // data[j] - 'a' + 10
        }
        else
        {
            b = 0;
        }
        ((char*)(&value))[n] = (a * 16) + b;
        --n;
    }
    return value;
}

Philip Prins · Apr 25, 2017

wonder said:

Not tested...

B4X:

#include <inttypes.h>

typedef unsigned char byte;

float FloatFromHex(char* data)
{
    float value;
    byte i, j, k;
    byte n = 3;
    for (i = 2; i < 9; i += 2)
    {
        j = i - 2;
        k = i - 1;
        byte a, b;
        if (data[j] >= '0' && data[j] <= '9')
        {
            a = data[j] - 48; // data[j] - '0'
        }
        else if (data[j] >= 'A' && data[j] <= 'F')
        {
            a = data[j] - 55; // data[j] - 'A' + 10
        }
        else if (data[j] >= 'a' && data[j] <= 'f')
        {
            a = data[j] - 87; // data[j] - 'a' + 10
        }
        else
        {
            a = 0;
        }
        if (data[k] >= '0' && data[k] <= '9')
        {
            b = data[k] - 48; // data[j] - '0'
        }
        else if (data[k] >= 'A' && data[k] <= 'F')
        {
            b = data[k] - 55; // data[j] - 'A' + 10
        }
        else if (data[k] >= 'a' && data[k] <= 'f')
        {
            b = data[k] - 87; // data[j] - 'a' + 10
        }
        else
        {
            b = 0;
        }
        ((char*)(&value))[n] = (a * 16) + b;
        --n;
    }
    return value;
}

Tnx But this is in C,i need it for B4J

If i use Bit.ParseInt("5836", 16) i only get the decimal 22
I need 22582

Philip Prins · Apr 26, 2017

Philip Prins said:
Tnx But this is in C,i need it for B4J

If i use Bit.ParseInt("5836", 16) i only get the decimal 22
I need 22582

Solved it , 36 are the first 2 digits, 58 the second 2 digits

B4J Question Convert HEX to Float

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