Turning parts of hex string into little endian

Hi

Im trying to write a program that will test some stuff at work and the protocol they have made is buildt up like this:

Prelim (always the same) , length (of data field),senso. no, adress, data and crc.

The CRC is calculated from all except prelim, little endian on all fields (turned after crc-calc) on everything but prelim.

Can someone pleas help me?

Can you post some examples that show the contents of the input and the desired output?

Here goes

Code:

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utb2sio 04 01 00 08 2b 45 // in big endian

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I do have all the diffent parts of the string in separate strings that I combine.

The data field content is preset in the protocol.

What does that post show? Is it a String with spaces between the parts or what?
Can you post the input and show what output you want from it?