Help for setting the formatSpec when reading hexadecimal

Hello, this is Matthew.

I'm trying to read a file that contains hexadecimal. This is the pattern. Or check the attached file, please.

00b7 17ff 5b3f 1700 c84b 1eff b398 1d00

a577 00ff 15b3 00ff 00b7 17ff 5b3f 1700

c84b 1eff b398 1d00 a577 00ff 15b3 00ff

00b7 17ff 5b3f 1700 6929 1eff b398 1dff

a577 00ff b690 00ff 00b7 1700 5b3f 1700

6929 1eff b398 1dff a577 00ff b690 00ff

So I wrote that

formatSpec = '%04x %04x %04x %04x %04x %04x %04x %04x\n';
fid = fopen(filename, 'r');
hex = fscanf(fid, formatSpec);
sizeHex = length(hex); % the length shows 0

How should I change the format spec to read the hexadecimal correctly?

-Regards, Matthew

Answer 1

[Walter Roberson]

That file does not contain hexadecimal. It is a binary file. You can use

data = fread(fid, '*uint16', [1 inf]);

If you want to see the hex equivalent you can

disp(dec2hex(data))

Watch out for byte order questions. The above code will treat the byte stream as being the in-memory byte order, which is "little endian" -- the first byte of the file would be the low byte (least significant) of the uint16. You can add 'ieee-be' to the fopen() to have it treat the first byte of the file as the high byte (most significant) of the uint16.

[Matthew Kyeo]

Thanks for your kind reply, Walter. May I ask one additional question?

As you saw my attached file, the first line goes like this;

abf3 1700 8463 17ff 7de4 1e00 23d5 1cff

Your code

data = fread(fid, '*uint16', [1 inf]);

reads the first input (abf3 in little endian, 62379) correctly.

I expected to read 1700, 8463, 17ff, ... in little endian. However,

Matlab read 33792 (skipped 17 and read 8400),

65303 (skipped 63 and read 17FF), and so on.

Is this due to the space/tab in the file?

What option should I add for the fread function?

-Regards, Matthew

[Walter Roberson]

Sorry, should be

data = fread(fid, [1 inf], '*uint16');

[Matthew Kyeo]

You don't have to apologize! :D

You saved my life. Thanks~

-Regards, Matthew