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Taranis, Crossfire & Spektrum

#1
Question: When I ordered the Opterra, I didn't take into account possible compatibility issues between my radio - Taranis XD9 Plus, and the Spektrum receiver/fc on the wing. If I use the Crossfire micro tx module & receiver in the Crossfire compatible Opterra, does that overcome the issues of using the Taranis radio, or do I have to buy a Spektrum radio as well?
 

makattack

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#2
I suppose if you have a the Crossfire system, and already have the Crossfire equipped Opterra, you'll have no problem. If not, then your other options are to either get a Spektrum module for your X9D+ (I personally have two, one was a DIY module with the RF chip pulled from a DX4e, and another one is the iRangeX STM32 Multiprotocol Module) which you can use to bind over DSM to any spektrum receiver. Another option yet is to pull the RX from the Opterra, and use whichever favorite RX you desire in whichever protocol you choose.
 
#4
Thank you Makattak for your reply. A couple more questions: after plugging in the crossfire rx into the receiver of the opterra (which, in horizon hobby’s video, says it is plug and play), my understanding is that the x9d+ is essentially a crossfire tx/rx setup, and that the spektrum aspect is pushed aside. If that is the case, then I think I’m already set. If that isn’t the case, then which multi protocol module is the one to get, and what would be the process for integrating it? Also, does the multi-module allow for using a module like the crossfire to extend range/ strengthen signal?
 

makattack

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#5
According to page 4 of the manual https://www.horizonhobby.com/pdf/EFL11460-Manual-EN.pdf you're actually plugging the Crossfire RX into the Flight Controller (NOT the RX that comes with it) so you would probably be removing the BNF RX (a Spektrum RX presumably) and replacing it with the CRSF receiver plugged into the CRSF port. So, you're actually physically removing the Spektrum RX to use a Crossfire RX instead. I have no idea what would happen if you have both plugged in, but I suspect nothing good would come of it.

You would only need a multiprotocol module if you didn't already have the crossfire system. If I were a crossfire owner, I would probably use that over the multiprotocol options, unless you also needed the multiprotocol module for other stuff. I think the newer multiprotocol commercial offerings are easier to use, but the one I have requires using a FTDI USB serial interface, an Arduino IDE, and the DIYMultiprotocol software to update (and I had to update from what shipped with my iRangeX module in order to get a working/non buggy setup). I would say if you're not comfortable with all that, the crossfire option is even more appealing.

Here's all the info you'd ever need on the multiprotocol module:
https://github.com/pascallanger/DIY-Multiprotocol-TX-Module

Again, the multiprotocol module has nothing to do with crossfire. Doesn't work on the same frequencies. Crossfire is it's own system for RC control and is designed for long range. Presumably, you need to be a amateur radio operator for that as well (I'm guessing, as I really don't know much about crossfire, but assume it's UHF). The multiprotocol modules and DSM all operate on ISM bands (basically wifi/microwave) and are not meant for long range.
 

ElectriSean

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#6
Again, the multiprotocol module has nothing to do with crossfire. Doesn't work on the same frequencies. Crossfire is it's own system for RC control and is designed for long range. Presumably, you need to be a amateur radio operator for that as well (I'm guessing, as I really don't know much about crossfire, but assume it's UHF). The multiprotocol modules and DSM all operate on ISM bands (basically wifi/microwave) and are not meant for long range.
Crossfire is UHF, but it is also digital spread spectrum and FCC licensed so no amateur license is required.
 
#7
Okay, so as I understand things, crossfire hardware takes over from the spektrum hardware, and communicates directly with the flight controller via the module plugged into the back of the x9d+, and the opterra flight controller has provisions to work with the crossfire rx. Essentially, when is a taranis not a taranis? When crossfire is plugged into it. The, AS3X & SAFE Select and GPS module all carry on as intended, because they're in the flight controller, and FPV is its own function. Correct? As best all of you know?
 

makattack

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#9
Yep, just like you can also use Crossfire on a Spektrum TX, I believe, via the PPM/trainer port. Based on my looking into it more. I'm also tempted to look into crossfire for my own use, but then again, don't really have a need for it. More out of geek curiosity.

You may want to look into this video for a more detailed description of RC electronics:

Then, maybe for flight controllers:
 

ElectriSean

Eternal Student
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#10
Yep, just like you can also use Crossfire on a Spektrum TX, I believe, via the PPM/trainer port. Based on my looking into it more. I'm also tempted to look into crossfire for my own use, but then again, don't really have a need for it. More out of geek curiosity.
It really is a fantastic system, and the newer 'starter kit' drops the price of entry quite a bit if your Tx has a module bay.
 
#11
It really is a fantastic system, and the newer 'starter kit' drops the price of entry quite a bit if your Tx has a module bay.
I read about using crossfire on spektrum radios, via the trainer port, and in doing so supposedly increases latency a noticeable amount. Flying a plane around a park, with adequate margins of space, that may not be an issue, unless 'something unexpected happens' and your margin disappears, you're left with hoping your inputs are in time to overcome the latency to save your plane.

Again, thank you to all the knowledge base reaching out to lend me a hand in sorting out what is likely to be a great setup. Once everything arrives, I'll get it put together and I'll let you all know how it worked out.
 

ElectriSean

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#12
I read about using crossfire on spektrum radios, via the trainer port, and in doing so supposedly increases latency a noticeable amount. Flying a plane around a park, with adequate margins of space, that may not be an issue, unless 'something unexpected happens' and your margin disappears, you're left with hoping your inputs are in time to overcome the latency to save your plane.
Unfortunately that's the nature of the CPPM trainer port. It is only slightly worse latency than the standard PWM used by planes and servos, you really wouldn't notice it. Where it can be an issue is with multirotors, the actual CRSF protocol is faster than SBUS and when using a serial interface (as it does with a Taranis) it's a noticeable difference. Still not terrible though, a few years ago CPPM was all the rage in multirotors as it greatly simplified wiring over PWM.