Long ago in a galaxy far far away I built an RC solar plane.
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?
Take a stab at it! Last Friday I went the complete opposite direction and flew without an RC Tx. I tried out the joystick only functionality of Mission Planner on my APM1 quad using APC220 modems. Using a Logitech 3d pro joystick, there are enough buttons to set every AC2 mode available. The whole flying experience with a joystick was interesting, to say the least. :)
Very cool idea. I wanted to do the same thing- 1transmitter, 1reciever, ALL the data in/out. My concern was bandwidth in the Xbee system. I am using the 2.4gHz turnigy 9x too, 900mHz Xbee, and will use the new 1.3gHz for FPV and photos. I'd love to be able to integrate all of these into one system. I don't have alot of radio expertise- enough to be dangerous as it were. Where to start? I have almost nothing to offer but enthusiasm.
i read somewhere there was too much latency with the xbees for RC control but i know I've seen it done i think it was on Lynxmotion http://www.lynxmotion.net/
I am doing something similar with USB flight controllers and a little industrial PC on the ground connected to a 900MHz radio and in the air coming out of the 900mhz radio via serial to a micro which converts my data stream to PPM. I wanted to use a mod5270 onboard but I have a hell of a time coding the easy stuff as it is. I am using the same radio for video, as they also have Ethernet, with good results.
with your own tx you could add more switches and place them too your liking and have telemetry and or use a wii controller we kinda already have that with the MP but have to depend on windows (scary)
I am using the Flyton LRS 433 mhz long range module and RX with my Turnigy 9x. You can configure the RX to send a transparent low baud rate serial link along with the PPM signal.
I want to either loose the xbees or RC transmitter. I need to try the joystick mode through the xbees.
I don't think the 17bytes/sec transparent uplink would be fast enough to use the joystick mode. I fear that it would add too much latency to make manual control possible. What it does allow you to do is send commands to the APM, such as nav points, rtl, land, etc.
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."
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.
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.