Is anyone inclined to give the J1b no DUO a tryout? The .bit file is at: https://github.com/jamesbowman/swapforth/raw/master/j1b/xilinx/j1-papilioduo.bit If you load it, it should be possible to talk to it over the UART at 921600: There are more details in the reference manual on page 5: https://github.com/jamesbowman/swapforth/raw/master/j1b/doc/j1b-reference.pdf And to get the whole system, clone this tree and look under j1b/: https://github.com/jamesbowman/swapforth