How to convert a string into hexadecimal in Bash

Question

I've found many posts on StackOverflow which have covered this question in C++, C# and other languages, but none with Shell.

Using Bash/Shell, how do I convert a random String into a byte array?

I tried:

echo "some string" | xxd -r -p

but it didn't work.

I basically want a byte output - e.g. )?e?GV??vY?Ge?#G