The code here is a slightly modified version of what can be found here:
github.com:mrehkopf/sd2snes.git and/or there:
git@github.com:borti4938/Switchless-Mods.git (the later is seems to be gone..)

The story:

I had a working .hex file which I had downloaded from one of the above repos
about 1 year ago. Recently I wanted to make sure I had the correct source code
for it.

But when I compiled the source (with the version of gpasm included
in Debian being 1.4.0) it resulted in a non-functional .hex file.
The LED would blink, but my game would not run.

So I disassembled the working .hex file to find out how it differed from the version
I compiled myself, and made the required changes to the source here
so I would get an identical (and working) binary.