Hi all,

I Have a plan to build my own handheld groundcontroll station and was thinking about the 2,4ghz rc side of things... With having  a 433mhz telemetry uplink is there any need for a Traditional RC link?

If my Thinking is correct the 3DR Solo uses the Telemetry signal for RC controll Too, Correct me if im wrong! If they can do it why cant we? I know mission planner has an option for a "joystick" but there is also a need for the rc link aswell, Maybe the code would have to be tweaked?

Just an idea at the minute but What I would like to do is have a android stick on a 7" HDMI monitor runing droidplanner with a joystick conected for RC. (something similar to my image, just diy)

What do you guys think?

Views: 1351

Comment by Brian on September 20, 2017 at 1:43pm

If your controller can output PPM, you can do it with a pair of OPLink modems.

Comment by Nicholas Witham on September 20, 2017 at 7:24pm

The benefit of having an RC link as well as having a separate telemetry link is for redundancy. If you lose one, you'll still have the other.

If you only want to use one there are a number of options:

You can use a USB/bluetooth controller hooked up to your computer in mission planner to use as a controller for your aircraft (There is a setting to turn off the requirement for an RC link), but that will obviously be sent through the telemetry link as MAVLink data, which takes much longer to encode/send/receive/decode than just sending an RC signal in tandem with the telemetry. You can ramp up the speed of the telemetry link, but as you do that, you lose distance. There are lots of options of telemetry links, there are the 3DR 915 or 433 MHz telemetry modems (and the million clones of them), OPLink modems, RFD900 modems, plus many more.

Another thing you could use is hardware that sends an RC signal (not mavlink) inline with telemetry data (Mavlink). What this does is take an SBUS or PPM signal and send it with the telemetry data all together. Such items include TBS crossfire, dragonlink and RFD900+.

The next thing you could use is something that sends RC (SBUS or PPM), telemtry (MAVLink), and HD video all over WIFI. Items that can do this are "Solo Link", or "CUAV Hack Link", plus a couple others under development right now.

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There are literally thousands of people that have done these or variants of. One thing that is common though is connecting a number of joysticks and buttons to an arduino and getting that arduino to output a PPM signal, then transmitting that signal to their aircraft with a dedeicated RC transmitter module. They also may use this RC module in parallel with a telemetry link.

Comment by Brian on September 20, 2017 at 8:47pm

The OPLink sends the RC signal inline with telemetry, and has since 2013 - well before TBS crossfire, dragonlink, and RFD900+ have been around. Longer than 3DR modems have been around for that matter.

You really don't want to send control information over the normal telemetry link, especially passing through a PC and additional RF links. It adds too many points of potential failure, and additional latency and jitter.

Comment by Nicholas Witham on September 20, 2017 at 9:54pm

@Brian, i didnt realise that about OPLink. nice.

I agree with your statement regarding RC over telemetry. definitely not a good way to do it.

Comment by Marc Dornan on September 21, 2017 at 2:17am
Combined telemetry and rc links are a compromise in terms of performance of course. TBH OPlink has not been a great performer for me and others and has not been developed for some time. I would not select it for a controller now. Dragonlink has the benefit of having, I believe, transparent 19k serial telemetry and a wide user base and very long range performance. It is not especially cheap. RFD900+ supposedly does the same but I have not seen so many users. I think both use capable 32 bit MCUs.

There are some great 433 1W LORA modules now that do long range telemetry. A really robust inexpensive approach is to use a FrSky LR9 and a 1W Lora module for telemetry. Maybe 10k range with good antennas.

This project is gaining momentum. It uses said LORA modules to do PPM and Telemetry. https://www.rcgroups.com/forums/showthread.php?2837542-QCZEK-LRS-DI...

Also Jordi at M Robotics says he will have an improved Sololink for sale soon. That will do HD video, RC, and telemetry in open source hardware. Prob about a mile range.
Comment by Brian on September 21, 2017 at 8:23am

I don't know what problems you had with OPLink, but there have been some bad batches of OPLink clones that have shorted antenna connectors. Unfortunately, the hardware is all clone hardware at this point, but the firmware is still supported by the LibrePilot project.

One current OPLink user has recorded ranges of over 8km using stock (100mW) hardware and running control + a full 56kbs telemetry link.

I've been wanting to try LoRa, but LoRa is really designed for very low bit rates, I think you could get control information through a true LoRa link, but I don't think you can get full telemetry without switching back to FSK.

Comment by Nikola Rabchevsky on September 21, 2017 at 9:59am

It's not just about the frequency.  Sure, 5.8 GHz is less crowded but 2.4 GHz inherently gives you better range and signal propagation through foliage.  IMHO, the elegance of the Solo design is that there is one RF link handling everything (one link to rule them all and in the darkness bind them).  It's proof that it can be done and can be done seamlessly.
While I am a fan of DIY, I appreciate great design over MacGyver setups.  As Scotty once said, "The more they overthink the plumbing, the easier it is to stop up the drain."  Sometimes you just need to get the job done and you don't have time to mess around with a lot of equipment.

I think that 3DR's Solo design is the happy medium between DJI's tight integration and open-source flexibility.  Hopefully, the gimbal and the iOS app will go open-source soon.

Comment by luke cooke on September 21, 2017 at 11:05am

Some good point here! I think what i would like to do is keep it as simple as possible, Anyone should be able to buy the same parts and copy me. Im not really looking on over complicating things and just thought that maybe i could use the Telemetry for the RC side. That looks like its not the way to go.

As for OPlink i have never used one bofore and would prefer using someting I know and trust, I am now thinking of staying with my FRsky system for the rc.

So maybe design a new case for the taranis with a 7" touch monitor in the middle running droidplanner, Easycap usb tv dongle for video input, smal Eachine DVR and a realacc 5,8ghz VRX. Ill probably do the case as a 3d design and upload it to thingiverse and Shapeways. Anyone used shapeways before? Still thinking about what orientation to have the monitor, vertical or horizontal?

Comment by Nikola Rabchevsky on September 21, 2017 at 7:54pm

I'm surprised that a company like Futaba hasn't come up with a radio that uses wifi, an iOS or Android tablet as a user-interface, and has a video feed.  Hell, they sell a friggin' $3000 radio that does nothing more than their $1000 radio.

Comment by Nikola Rabchevsky on September 21, 2017 at 7:56pm

And I have to say that I'm not a fan of joysticks that I can't pinch.  Thumbs, IMHO, are not a precision instrument.

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