AVR-Chat

> [...] and the AVR return the bytes in reverse order "1000" 
> but in binary = 0x31303030hex = 825241648dec

This is pretty simple.  If you have source code for both ends of the 
comm channel, then modify one end to match the other.  If you only 
have source code for one end of the channel, you'll have to modify it 
to match the byte order of the other end.  Done.

Hint: don't use any library functions unless you know exactly what 
they do.