Notices

Howdy

It has occured to me, that the N900 has several features that would be really useful in flying model planes. For example the accelerometer, camera and the GPS (altimeter and speedometer).
Writing the software for this shouldn't be too hard, and if the camera isn't used it could be text only.

The only problem I can think of this is the wireless range. What would have the best range out of the wifi or bluetooth radios? I'm thinking of having a laptop at the flying field to recieve the signal, or ssh into the phone for the text only solution.

Is it possible to get a range of a few hundred meters (through air) with any of the radios on the n900? If a text only solution is used then it would be possible to get away with a very low data transmission rate. Perhaps only a few bytes per second. although I have no idea whether this is possible with the radio stack on the n900.

Thanks.

Joe.

I suppose this would be for telemetrics only (and maybe a video feed) ? It's a kinda cool hack idea but the N900 is kinda heavy to be put a flyer (unless it's a rather large one) and it needs to have unobstructed view of the sky for the GPS to work optimally (CF is pretty good conductor AFAIRecall so it will probably block GPS signals).

Bluetooth will likely be a problem, wifi should not be since you have full LOS (Line Of Sight) and of course you could put a better antenna to the laptop end (actually it might be a good idea to use a base-station [with good antennas] that both the n900 and the laptop connect to rather than ad-hoc).

However the modern radios that operate on 2.4Ghz might get interference from the WiFi (also 2.4Ghz...) so even if you use old-fashioned radio (like I do) if you're on a field with other people it might not be the best of ideas...

I just put a small camera and video transmitter on my RC heli but as stated I have old 35Mhz radio so the 2.4Ghz video tx does not interfere (and I have plenty of flying space on my own "yard" [2ha] so no need to worry about other people). Unfortunately I was paying too much attention to the wrong things (like how well the video feed worked) and touched ground with the tail rotor, stripping gears from tail servo, and things went downhill from there (actually seems I only stripped gears from a cyclic servo in the resulting crash, need to dismantle the rotor head still to check if the feathering shaft got bent)

I'm sorry to hear about your crash.

Having posted a similar thread here it seems as though this probably isn't the best solution to the problem. The n900 is substantially heavier than the standalone components would be. And as I'm sure you know, keeping your eyes on the model is pretty important. Although perhaps having a "co-pilot" manning the instruments might work.
I don't think that interference should be much of a problem although it would be important to test this before take-off.

I wonder whether it would be possible to use the gprs radio though. Directly to the laptop, the latency from the cell network would be too great to be useful.

Having the fpv goggles and a hud would be very cool indeed.

</rambling>

Then to the actual software side:

Making a simple telemetrics package to poll, store and send the GPS and accelometer data should be simple (can be done in python if you don't mind the [relatively small] overhead). This could even be sent over GPRS link.

I'm not sure whether it would be better for the N900 to push the data streams to a server on you laptop or have a simple server process on the n900 your laptop can pull the data from. Probably running a server on laptop and a simple pushing client on N900 is better (less work for the N900).

Video is more tricky, I guess you could tunnel X11 but that's about as bandwidth inefficient as it can be (though probably would be easiest to set up as a proof of concept).

What I had in mind for the first few flights was just a very simple program outputting the altitude (minus starting altitude) and the speed to the terminal, and then sshing into the phone from the laptop.

As for the video, a skype video call (or similar service) might be ok I suppose. Although I really know very little about how well that would work.

Helis crash, one needs to accept that if one wants to play with them...

I don't really know, not ever having tested but when I was first planning the video tx xfade mentioned that it might not be a good idea if I have 2.4Ghz radio (of course wifi has active interference avoidance in itself so it's different...)

You would need to run your own picocell, "theoretically possible".

yup, the problem is that suitable display goggles with sensible resolutions are still horrendously expensive.

I don't know enough about the radio systems used. But don't the Futaba radios use the faast system, hooping over many many channels very quickly. Again, I don't know nearly enough to tell whether this would make a difference.

Are you by any chance a Linux user? The hardware is there, somebody will patch support together eventually.

Yeah, having just looked into the goggles, they do seem a bit pricey. Maybe it would be easier to stick to in flight recording. A very expensive black box.

What about using something like a Nokia 6230 (nuron in the USA) which is a very cheap (£80) nokia touchscreen phone running symbian 5th edition. It has GPS, accelerometr, and ready made software with sports tracker.

damn sight cheaper than a N900 when/if it falls out not of the sky.

Among other things, I use OSX mainly and Linux (+OpenSolaris) on the side. There is some developments in open GSM basestation space but there is all kinds of regulatory issues so wifi is the realistic option.

Symbian development is pain (if we still have the goal of sending telemetrics back instead of using it as flight recorder).

Anyways for flight recorder there are lighter packages actually designed for that use.

Anyway it would be significantly lighter to use some embedded computer board with gps and wifi (or maybe just a simple serial radio link), gumstix makes those but they're a bit pricey... I have for playing around an TelIT GSM+GPS module that has bunch of GPIO pins so adding accelometers would not be an issue (though it has only GPRS, no wifi) the nice thing about the TelIT is that it runs python code (v2.2 and no floating point and some other embedded environment constraints make it slihtly painfull regardless)

"bit pricey", the consumer stuff from Vusix is somewhat sensibly priced but I have no idea how well the see-trough actually works on them (they're designed for watching movies not for HUD).

http://store.vuzix.co.uk/euro/acatalog/Wrap_920.html

And stuff designed to be usable as HUD is priced for the military and other specialist organizations:

http://www.inition.co.uk/inition/pro...e&SubCatID_=15
http://www.inition.co.uk/inition/pro...0&SubCatID_=15
http://www.inition.co.uk/inition/pro...3&SubCatID_=15

I have been waiting for ten years for reasonably priced properly HUD-capable wearable displays and while the specifications get better the price does not get much nearer the sensible range.

Edit: Some more HMD geek pr0n: http://www.inition.co.uk/inition/products.php?CatID_=8