Hexadecimal Data Convert to signed int32

Hello everyone!

I'm try to convert from hexadecimal data to signed int32. Here is my matlab code:

----------------------------------------------------------

Gyro_const = 1.08507e-6;

rawdata = [

"0a" "31" "00" "00"

"14" "cf" "ff" "ff"

"8f" "13" "00" "00"

"36" "ce" "ff" "ff"

"cf" "1a" "00" "00"

"83" "f3" "ff" "ff"

"9e" "fc" "ff" "ff"

"82" "eb" "ff" "ff"

"17" "1b" "00" "00"

"c9" "da" "ff" "ff"

"65" "1e" "00" "00"

"14" "dc" "ff" "ff"

"e8" "29" "00" "00"

"c9" "cb" "ff" "ff"

"29" "1b" "00" "00"

"32" "ef" "ff" "ff"

"80" "f8" "ff" "ff"

"b0" "ec" "ff" "ff"

"29" "23" "00" "00"

"09" "cf" "ff" "ff"];

%for i = 1:size(rawdata,1)

for i = 1:2

data = rawdata(i,:);

fprintf("non Inverted Data\n")

[data(1),data(2),data(3),data(4)]

fprintf("Inverted Data\n")

[data(4),data(3),data(2),data(1)]

double(int32(hex2dec(strcat(data(4),data(3),data(2),data(1)))))*Gyro_const

end

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I run this code in 2 steps and output like this:

ans =

1×4 string array

"0a" "31" "00" "00"

Inverted Data

ans =

1×4 string array

"00" "00" "31" "0a"

ans =

0.0136

-------------------

non Inverted Data

ans =

1×4 string array

"14" "cf" "ff" "ff"

Inverted Data

ans =

1×4 string array

"ff" "ff" "cf" "14"

ans =

2.3302e+03

Of these two values "0.0136 ","2.3302e+03" comes from "0000310a", "ffffcf14" hex values.

These values convert via hex2dec() built-in function.

I manually check hex value to decimal conversion but there are problem for me, this problem caused by hex2dec() function: For example:

hex2dec(strcat("00","00","31","0a")) -> 12554 This is true value for me. But the second iteration conversion is

hex2dec(strcat("ff","ff","cf","14")) -> 4.2950e+09 This is wrong value for me.

I think this problem based on the hex2dec int32 conversion. So my question how can I the hex2dec function output:

I mean, I know that this conversion hex2dec(strcat("ff","ff","cf","14")) actually -> -12524 value.

But my result is 4.2950e+09.

My question:

How can I set hex2dec function output, signed int32? or is there a any different solution for my problem.

Kind Regards.

Answer 1

[Les Beckham]

The hex2dec function assumes unsigned integer unless you tell it otherwise. You can either typecast the unsigned result to signed or use a suffix (e.g. 's32') on the string or char vector that you pass to hex2dec. I've shown both approaches below. Note that using the suffix only works on R2020a or higher.

Gyro_const = 1.08507e-6;
rawdata = [   
    "0a"    "31"    "00"    "00"
    "14"    "cf"    "ff"    "ff"
    "8f"    "13"    "00"    "00"
    "36"    "ce"    "ff"    "ff"
    "cf"    "1a"    "00"    "00"
    "83"    "f3"    "ff"    "ff"
    "9e"    "fc"    "ff"    "ff"
    "82"    "eb"    "ff"    "ff"
    "17"    "1b"    "00"    "00"
    "c9"    "da"    "ff"    "ff"
    "65"    "1e"    "00"    "00"
    "14"    "dc"    "ff"    "ff"
    "e8"    "29"    "00"    "00"
    "c9"    "cb"    "ff"    "ff"
    "29"    "1b"    "00"    "00"
    "32"    "ef"    "ff"    "ff"
    "80"    "f8"    "ff"    "ff"
    "b0"    "ec"    "ff"    "ff"
    "29"    "23"    "00"    "00"
    "09"    "cf"    "ff"    "ff"];
%for i = 1:size(rawdata,1)
for i = 1:2
    data = rawdata(i,:);
    fprintf("non Inverted Data\n")
    [data(1),data(2),data(3),data(4)]
    fprintf("Inverted Data\n")
    [data(4),data(3),data(2),data(1)]
    % double(int32(hex2dec(strcat(data(4),data(3),data(2),data(1)))))*Gyro_const
    double(typecast(uint32(hex2dec(strcat(data(4),data(3),data(2),data(1)))), 'int32')) * Gyro_const
    double(hex2dec(sprintf('0x%s%s%s%ss32', data(4:-1:1)))) * Gyro_const
end

non Inverted Data

ans = 1×4 string array
    "0a"    "31"    "00"    "00"

Inverted Data

ans = 1×4 string array
    "00"    "00"    "31"    "0a"

ans = 0.0136

ans = 0.0136

non Inverted Data

ans = 1×4 string array
    "14"    "cf"    "ff"    "ff"

Inverted Data

ans = 1×4 string array
    "ff"    "ff"    "cf"    "14"

ans = -0.0136

ans = -0.0136

[Stephen23]

Note that the loop is not required:

format long G
Gyro_const = 1.08507e-6;
rawdata = [   
    "0a"    "31"    "00"    "00"
    "14"    "cf"    "ff"    "ff"
    "8f"    "13"    "00"    "00"
    "36"    "ce"    "ff"    "ff"
    "cf"    "1a"    "00"    "00"
    "83"    "f3"    "ff"    "ff"
    "9e"    "fc"    "ff"    "ff"
    "82"    "eb"    "ff"    "ff"
    "17"    "1b"    "00"    "00"
    "c9"    "da"    "ff"    "ff"
    "65"    "1e"    "00"    "00"
    "14"    "dc"    "ff"    "ff"
    "e8"    "29"    "00"    "00"
    "c9"    "cb"    "ff"    "ff"
    "29"    "1b"    "00"    "00"
    "32"    "ef"    "ff"    "ff"
    "80"    "f8"    "ff"    "ff"
    "b0"    "ec"    "ff"    "ff"
    "29"    "23"    "00"    "00"
    "09"    "cf"    "ff"    "ff"];
double(typecast(uint32(hex2dec(join(rawdata(:,4:-1:1),""))),'uint32')) * Gyro_const

ans = 20×1

1.0e+00 * 0.01362196878 4660.32657445404 0.00543294549 4660.3263335685 0.00744683541 4660.33669490193 4660.3392242001 4660.3344715935 0.00752496045 4660.32982640883

[Rasit]

Really Thnx!

[Les Beckham]

@Rasit

You are quite welcome.

If this resolves your issue, please click "Accept this answer". Thanks.