Ok I now have a reasonable display. The schematics for the Arduino rotator control show pin 15 and 16 NC which I did wonder about. That’s the backlight. ;)
RTSL Found a couple of MEMORY saving defines. I don’t really care about anything but the Yaesu commands so it all fits.
Now it just seems to hard swing the azimuth full scale to the right. No shorts that I can see. I guess I’ll do more debugging after lunch.