Alternate Transmitter/Telmetry scheme...
Long ago in a galaxy far far away I built an RC solar plane.
http://www.rasdoc.com/splinter/solar2004.htm
I have a lot of switching power electronics on this plane and it was before 2.4Ghz radios were common. The power electronics caused interphereence with both 50 and 72Mhz RC transmitters.
So I made a system where I replaced the module on the back of my JR transmitter with a little CPU that read the PPM signal and used a maxstream 900Mhz radio to talk to the plane.
The plane could also send down telemetry on the same channel.
Today I see a lont of work being done to add telmetry to things like the custom turnigy 9x builds etc... yet they still use two radio systems, a (usually) bi-directional telmetry system and a separate RC transmitter.
So my question is this why not modify the Turnigy so it sends serial commands containing all the info normmaly used in a PPM signal via a serial conenction via a xbee (either 2.4G or 900M version) and have the quadcopter autopilot use that as both telemetry and RC communication?
Then roll the APM pllaner info into the Turnigy and have a simpler system with more capability and less parts?
I spent the evening digging through all the turnigy 9x modifcationt hreads on the net and conceptuall this seems like a simpler solution that what a lot of people are doing with two complete radio systems?
If you switch to 900Mhz bi directional telmetry/controll channel, you'll get longer range than 2.4G and also open your self up to using the really low cost 2.4Ghz wireless video systems?
Any thoughts?
Paul
Replies to This Discussion
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ModeratorPermalink Reply by Monroe on -
You think the joystick control wont work even for a slow flying stable plane?
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Permalink Reply by arashi on -
I just don't know. Since the TX and RX are opensource Arduino based, and you can flash the turnigy9x with opensource software, I am sure there is some way to tweak it to use less control channels at a lower refresh rate. I know that by default, the Flytron uses 3 set freqs and hops between them. If you get interference on a freq, the refresh rate goes down by a third
Again, I just don't know for sure. I've wouldn't want to try a multicopter with it.
quote from Flytron:
"Our original code does 3 channel frequency hopping (not FHSS, FH only) for reducing the risks. Standard refresh rate is same with your transmitter (50hz), if one of the channels disables by an external source refresh rate reducing to %66 (33hz) , if you loose 2 of 3 channels you can still fly with %33 (15hz) refresh rate.
If you didnt like it, you can write your own hopping codes or just use 1 solid channel."
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ModeratorPermalink Reply by Monroe on -
Yes, we wont need FH due to our use of a 3 meter tracking dish (well the dish is for the video link) a circular polarized Yagi for 433 Mhz will hang off the dish.
It's a back-up plan also for Arduplane so it may be ok. I say we find out :)
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Permalink Reply by arashi on
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I have all of the stuff, but I haven't yet tried the transparent serial link yet. Others have.
Yes, it is bi-directional. All of the LRS modules are RX/TX.
Apparently the uplink is limited to 17 bytes( not bits) bits per second to not disrupt the ppm signal.
The downlink is defaulted to 750 bytes/sec, but others have pushed it much higher.
It is all open hardware/software. There is code to use one of the modules as a quad controller in addition to its RX/TX duties. It would be interesting to adapt it to stabilize and control the camera on a balloon.
With the 7watt booster, you should have no problem with the uplink until you leave earth orbit... On the ground side, you can point a large yagi at the weak downlink.
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ModeratorPermalink Reply by Monroe on -
Arashi
Ok I'm making progress understanding what's going on here. The reason I'm having trouble is because this IS exactly what I need!
If the link can be sent to a pc from the Turnigy that could solve all my problems!
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Permalink Reply by arashi on
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The serial link terminates on the TX/RX module that you plug into the back of the Turnigy9x. You can just run a cable from the serial port header on the module to the PC. No problem.
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