First of all thank you very much for this work. A huge step in the right direction. On the other hand, it is a bit dated, and maybe no longer such a good starting point. So it is not clear what I should do.
What is most interesting in the README, is your mention of using signle port RAM. My understanding is that the J1 family requires dual port RAM, so I need to poke around in the code to figure out what you did.