writing a 16-bit binary file

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Robert
Robert on 12 Jan 2014
Commented: Walter Roberson on 8 Jul 2021
Hi there,
I am trying to produce a text file of 16-bit binary to test a C program.
I can write to a file, but it writes to the file in scientific notation. I am basically after a file with about 2048 lines of 16-bit ones and zeros or alternatively, just in standard form as in: 32767 -32768 not 3.2767e -4
if that could be put in the form of
0000 0010 1100 1000
kind of data that would be even better. I can only get this far. I am using a sine wave to generate the numbers, and the data only need be approximate, as it is to test a C routine that takes data straight from a circuit.
x = 0:1:1024; y = 32767*sin(x); fid = fopen('data.txt','w'); writebytes(fid, '%5.0d\n',y); fclose(fid);
kind regards Rob
  2 Comments
Asaad
Asaad on 23 Nov 2019
can i convert any binary number into 16 bit binary number ? If yes how what is the matlab code for it?
Walter Roberson
Walter Roberson on 23 Nov 2019
if isa(TheNumber, 'uint8')
output = uint16(TheNumber);
elseif isa(TheNumber, 'int8')
output = typecast( int16(TheNumber), 'uint16');
else
output = typecast(TheNumber, 'uint16');
end
If the original number was more than 16 bits wide then output will be a vector of uint16 . It is not obvious what 16 bit number you would want output if the input was, for example, a double.

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Answers (3)

dpb
dpb on 12 Jan 2014
doc fwrite

Jan
Jan on 12 Jan 2014
writebytes is thought for mupad objects. fprintf will be better:
fid = fopen('data.txt','w');
fprintf(fid, '%5.0d\n', y);
fclose(fid);

Robert
Robert on 12 Jan 2014
No, this is still giving me the text in the form: 3e+04
I need the data written in the file as either 16 bit binary, or just plain decimal if that is all matlab can do.
  5 Comments
dpb
dpb on 12 Oct 2017
Edited: dpb on 13 Oct 2017
I did go read; at least you did clarify there you are trying to write a stream file...the problem is undoubtedly in how you're holding the data internally; Matlab does "saturate" signed integers in some of the dec2hex and like but there's no issue in writing an unsigned int to stream file with fwrite.
I just did the same exercise as above excepting with
>> val=uint16(1:65535);
and verified each and every element is in the file...
We need to see precise code you used that cause the problem to be able to see where you went wrong, specifically.
But, the answer is probably shown by
>> v=int16(0:65535);
>> v(1)
ans =
0
>> v(end)
ans =
32767
>> sum(v==v(end))
ans =
32769
>> v(length(v/2)-4:length(v/2)+4)
Index exceeds matrix dimensions.
>> v(length(v)/2-4:length(v)/2+4)
ans =
32763 32764 32765 32766 32767 32767 32767 32767 32767
>>
OTOH,
>> v=uint16(0:65535);
>> [v(1) v(end)]
ans =
0 65535
>>
The problem is NOT fwrite, it's how you're storing the data internally; fwrite faithfully will output what's in memory.
Walter Roberson
Walter Roberson on 8 Jul 2021
By the way, these days dec2bin handles negative values.

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