I am doing the same. My base idea was 'controlling a model plane via IP network with cheap components'. I was quite sure I would not be unique in seeing this potential in the Pi
I am nearly there now:
- Have the base station software with HID joystick input (Linux, but easily adaptable to Win or Mac). It monitors link quality and allows to show sensor values from the model stations. It has provisions for mixing inputs or applying functions to them (set max/min values etc.), but that is not ready yet. I have planned for a long time to compete with the crappy software of most R/C transmitters that are sold for loads of money so I am very motivated to get good in this field .
- Have a videolink (very basic with a USB-Webcam and gstreamer, although I have provisions for it in the base station Qt software but it was more difficult than thought at first - anyway gstreamer is fine). Waiting what cameras will be available for Pi's CSI interface.
- Have the model software which controls servos and will be able to send sensor values from an altimeter/variometer sensor (BMP085 via I²C, 70% ready). btw, I use the same software for base station and model, it just loads different plugins. It is based on a simple UDP-protocol I made up, similar to a LAN-chat with auto-discovery. It runs headless (no GUI) on the plane to control it via a SSH session.
- since yesterday I have the servo control ready! Used a Pololu 207 mini board for that, driven via UART/serial. Typical latency over WLAN (adhoc-network, WPA2) is 30-50ms (which is a tad high for fast planes, but I want to stay with UDP/IP for simplicity).
- tested WLAN fidelity by putting the Pi onto my plane and the laptop next to me. Logger showed good connection up to 200-300m with my absolutely cheapish WLAN stick. Will need to dive into antenna/WLAN devices because I need 1000m for real free flight. Ping (roundtrip) times where 20-40ms in this range, up to 200ms when 500m away. Bandwidth is always enough for a videolink of 2 Mbps or the like.
The WLAN transmission is the weak point until now. Zigbee sounds good, but the high power devices (ranges of 80km lool) are not available in Germany and control via IP-network opens up a whole bunch of possibilities like smartphones, controlling a car via a browser etc. Additionally it is just plain simple and gives full control over your software via SSH which is very sexy (and the 1 big difference why I think a Pi has so much more creative potential than for example an Arduino).
I do not plan any autopilot capabilities so this cannot be a backup if the link is lost at distance. As long as I am not 100% sure, the Pi will fly with me but I still use the good old 35 MHz FM stock R/C link for control.
I am using the Laptop/netbook with a USB R/C transmitter as base station. Depending on what type of antenna will be needed on the base station (might be that this might get a bit special...), building the Pi into a used R/C transmitter and adding maybe a display to it is an idea, too. 1st-person-view-flying with glasses and head-up-display would make the display obsolete...