I think it's worth taking the time to describe the emulator's structure. As a picture is worth a thousand words, here's the general working diagram.

Inside the main housing is a Raspberry Pi running Raspbian. On top of it, an instance of yaAGC is executed at startup. This emulator usually runs Comanche 55, the original CM guidance software for Apollo 11. The emulator usually connects to yaDSKY, a virtual DSKY emulator through a TCP connection on port 19798. However, Ron Burkley and Mike Steward worked on a small python script that can send the keypresses and recover the display data. I slightly modified that script to output the display data through a serial link. I'll upload everything to my GitHub once I'm home :)

There are still some quirks though. Due to the many interfacing layers, the Nextion display often lags behind yaAGC and skips some registers. Same thing happens with the status lights, some of them stay on or off when they shouldn't. In the future, I'll bypass that Arduino Nano entirely and directly connect the Nextion display/alarm indicators to the Rpi's GPIO.