Interpreting character array as hex data
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Hi
I want to write a MAC address to a flash device. The address is generated by matlab and is in hex format, but strored as a character array (see code). When I write the variable to a binary file, matlab converts the characters to binary which is not what I want as my data already is hex formated.
macAddr = '0050c246d880';
fid = fopen('macAddr.bin','w');
fwrite(fid, macAddr);
fclose(fid);
% file content: "30 30 35 30 63 32 34 36 64 38 38 30" (hex interpreted)
I solved this problem by splitting the address into bytes and converting them to decimal:
macAddr = '0050c246d880';
% Split address to bytes and store them as decimal numbers
macAddrDec = '';
for i=1:length(macAddr)/2
macAddrDec(i) = hex2dec(macAddr(i*2-1:i*2));
end
fid = fopen('macAddr.bin','w');
fwrite(fid, macAddrDec);
fclose(fid);
% file content: "00 50 c2 46 d8 80" (hex interpreted)
This works, but isn't there an easy way to tell matlab that a character array is already hex formatted?
Cheers Simon
回答（2 个）
Walter Roberson
2012-2-13
0 个投票
You are mistaken in your interpretation that the data is being stored in hex in the file. The data is stored in binary and some program you are using is showing you the hex equivalent of the binary.
The character string is in the character representation of hex, not hex itself, and needs to be interpreted as binary in order to write it, using logic such as you have come up with.
2 个评论
Simon
2012-2-13
Walter Roberson
2012-2-13
fwrite(fid, sscanf(macAddr, '%2x'));
which is merely a more compact way and not a smarter way.
Jan
2012-2-13
You can write the data in CHAR format:
macAddr = '0050c246d880';
fid = fopen('macAddr.bin','w');
fwrite(fid, macAddr, 'char');
fclose(fid);
Walter suggested sscanf for the conversion from HEX to DEC already: This is much faster than hex2dec.
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