[Flightgear-devel] Sending flight dynamics data to serial port

[Tim Jelliffe]

Hi all,   First a bit of background to this request:   I am just starting off a thesis project for my engineering degree, with the task of building a cockpit mockup of a single engine light aircraft that my university has designed. Something in the same sort of class as a cessna 172. The aim is to have a functional cockpit, especially with regards to flight and engine instruments and controls.   I was already playing with flightgear, and decided to use this as the basis for the project, especially once i got the openGc addon working and found more about the network broadcast abilities of flightgear.   To control all the instruments I will be using either stepper motors ( altimeter etc), or air core meters (from car speedos, for airspeed etc) which are driven by a microcontroller (Mc68Hc11 to be exact). I know this is not the absolute easiest way of doing this, but it appeals to me as being one of the more powerfull ways of controlling a reasonable number of instruments, with all the control done by software.   I am looking at two ways of getting the data from the pc running flightgear to the microcontroller. My initial choice is to use a simple network card for the microcontroller, and use flightgear to broadcast udp packets at a set rate, which are then read, interpreted, and the instruments are driven to the right positions. This network card is a self-assemble job, which i have, but have not yet debugged to get it working.   The other option which may be easier, is to connect the microcontroller to the serial port, and somehow modify/add to flightgear the ability to transmit that same data directly to the micro. Connecting to the serial port is how I am programming the micro at the moment after all.   Some of the details for implementing these would be things like:   - finding a way to reduce the frequency at which the data is transmitted. Since things like the airspeed will really only be useful at integer values, there is probably not much value in continually transmitting data when the changes are well below the resolution of the instruments! I know that the rate of broadcast over the network is set by command line during startup, but is it possible or viable to make it only transmit when values have changed by a certain amount?   - if using the serial port option, to also receive a reply from the micro with the current values displayed, to be able to keep things in sync. (May not be required?)   I noticed in the IO readme, that there is an option for using 'serial' as the medium. Does this work as i assume, or is it only to help show the general form of the startup commands? The only other serial stuff is to do with NMEA, which as far as i understand is the format for gps, and so is not the whole flight dynamics data. Would a hack between the nmea and the fgopengc classes work to enable me to be able to transmit the OpenGC flight dynamics data onto the serial port?   Thanks for any comments to do with this.   Tim Jelliffe