The Pressure Altitude In wasn't reporting properly.I ended up pulling the unit and building a cable to allow me to dump the serial ports. I found that none of the altitude protocols worked. I sent a dump off to Bill Moffit at NavWorx. He suggested ALT EN protocol. That didn't work. Digging around, I found that I could set the sub-protocol that goes out on that port.
I selected GARMIN. The system worked once. But on a subsequent boot, not only did it not work, the GPS ALT (internal) stopped displaying. But if I look at the internal GPS packets, the altitude is there....
It was useful talking to Bill. I found that I needed to change the Control Port Protocol. I confirmed with Tim Hass at ApproachFastStack. That change let me control the ADS-B unit from the transponder.
