Hello Shapeshifter. Well actually The Bridge library is of interest, since I'll want to use the SD card too, as part of the whole scheme. Hadn't thought about the sketch in the 32u4 to D0, D1 but that is doable, of course. The 3.3 V Due isn't an issue but I have to see if a level shifter is needed interfacing to the DUE. And I still have to track down whether the SPI is also essential as it used in the Dragino application. (also no longer made). Thank you for the response, BTW. I know you are tuned into the YUN better than most on the Forum. I appreciate that.