This is an old revision of the document!
Beamer Serial
Our current beamer has an RS232 port, which can make it easier to control.
Without it, we need to power on the beamer, wait for the lamp to turn on, and then click on the source button, in hopes that HDMI is already plugged in. There is no guarantee that it'll stay on HDMI, unlike the commands you can send via serial.
We have a Sparkfun RS232 Shifter which can be used to shift the voltage (12V) down to a voltage usable by an ESP8266 (3.3V) or an Atmega328 (e.g. Arduino Uno/Nano) (5V).