Hex to float like python struct.unpack()

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Sebastian Thuné
Sebastian Thuné 2020-9-16
回答： James Tursa 2020-9-16
Hi
I'm trying to convert a hex string to a float in the same manner python function struct.unpack(), https://docs.python.org/3/library/struct.html , which is using the IEEE754 binary32 0r 64 depending on foat or double.
As an example I have
hex = 'C956F53D'
When i run it in a struct.unpack() i get the value:
data = 0.1198
And this is correct. However, when i try the following matlab function i get something totally different.
>> hex2dec(hex)
ans =
3.3779e+09
>> typecast(uint32(hex2dec(hex)),'single')
ans =
single
-8.8047e+05
Does anybody know the difference or what I'm doing wrong?
Thanks!

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采纳的回答

Ameer Hamza
Ameer Hamza 2020-9-16
This is the correct way
hex = 'C956F53D';
x = hex2dec(reshape(hex, 2, []).');
dec = typecast(uint8(x), 'single')
  2 个评论
Sebastian Thuné
Sebastian Thuné 2020-9-16
You my friend are a superstar! Thanks!
So i basically have to put the bytes in an array first. Why is that? Is it because typecast has to go byte by byte?
Ameer Hamza
Ameer Hamza 2020-9-16
编辑：Ameer Hamza 2020-9-16
Yes, you need to convert it into an uint8 array. Then MATLAB reads the bytes from the input array and converts those bytes into 'single'. It is pretty similar to pointer typecasting in C.
I am glad to be of help!

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更多回答（1 个）

James Tursa
James Tursa 2020-9-16
Could be a Big Endian vs Little Endian thing. E.g., inserting a swapbytes( ) step:
>> hex = 'C956F53D'
hex =
'C956F53D'
>> typecast(swapbytes(uint32(hex2dec(hex))),'single')
ans =
single
0.1198

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