writing a 16-bit binary file

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Robert
Robert 2014-1-12
评论： Walter Roberson 2021-7-8
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 个评论
Asaad
Asaad 2019-11-23
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 2019-11-23
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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回答（3 个）

dpb
dpb 2014-1-12
doc fwrite
Jan
Jan 2014-1-12
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 2014-1-12
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 个评论
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dpb
dpb 2017-10-12
编辑：dpb 2017-10-13
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 2021-7-8
By the way, these days dec2bin handles negative values.

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