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First Encounter With EdgeTX

I finally got a new radio for my RC planes, the RadioMaster TX16S, which is a 16-channel 4-in-1 with a touch screen. The channel count means that it has lots of ways to communicate to the planes (i.e., I can theoretically control many servos/actuators if the plane has a receiver that supports such controls) and the “4-in-1” means that it has support for multiple protocols – and can communicate with a lot of planes “out of the box.”

I have not flown anything with the TX16S yet. I’m still in the unboxing/setup process, and I still have things to do before I’m comfortable taking it out for real.

EdgeTX is a version of a radio-focused operating system called OpenTX. EdgeTX is updated in a lot of ways, primarily for touch screens, and theoretically has a number of UI updates as well (I have not used OpenTX, so I don’t have any prior experience to compare EdgeTX with.) The TX16S came with EdgeTX 2.7.1; the current version of EdgeTX is 2.8.0.

If that sounds a lot like Linux, particularly with bare-bones Linuxes like Debian or Slack and their user-focused counterparts like Ubuntu, well… it probably should, because that’s the way that it feels. OpenTX is “the real OS” and EdgeTX is the version for people who want to fly (as long as their radios support the requirements).

With the new radio, there are a lot of little things to do. If you’re an experienced flier, a lot of this will be “well, duh” material, and some of it will probably sound wrong and/or basic and/or horribly new. That’s okay with me; a lot of it probably is wrong and/or basic and/or horribly new. I’m writing this as a record, after all, and I’m learning as I go.

Getting Started

The first thing I wanted to do was validate that it could connect to my plane, a Horizon Hobby AeroScout 2.1 RTF. This is a beginner plane (which fits, as I am a beginner!), and comes with a Spektrum transmitter (the DSX, which is definitely an inexpensive starter radio) and receiver. Spektrum uses a specific protocol (called “DSM”) and support for this protocol is part of why I chose the 4-in-1 version of the TX16S transmitter; most of the planes I am likely to fly will probably have Spektrum receivers.

That calls into question why I bothered with the TX16S at all, actually: if most of the planes I’m likely to fly are Spektrum, why not get a Spektrum transmitter like the NX8, NX10, or whatever?

The reasons come down to cost and interest. Spektrum is good – excellent, probably – but it’s very expensive for what it is. The expense is not especially relevant, in that they’re designed to purpose (i.e., if you want to fly a plane with a Spektrum receiver, you … can use a Spektrum transmitter with little problem), but if you want to control anything else… well… they’re designed for specific receivers, as I understand.

The interest is the real thing, though. Spektrum is, as I said, designed to purpose: flying things that have Spektrum receivers. They do that well. But they’re not programmable; you get the transmitter, you use it as designed, end of story.

I’m an old-ish school Linux guy: not first generation, but relatively close to the second-wave, when Linux went from “hey, you can run this operating system and some programs actually run on it, too!” to “yeah, there’s probably a way to port it to Linux, if it hasn’t been done already” (and before the “wait, the source code has support for other UNIXes too?” period, when Linux basically took over the UNIX world.)

So OpenTX and EdgeTX, being programmable (and open source), have a lot of appeal for me on an intellectual level; one of the other pilots at the field was advocating for the NX8 very appropriately, saying “the purpose is to fly, not program,” and he wasn’t wrong at all… but my purpose is not just to fly, so the TX16S held a lot of appeal as a full-featured, programmable radio… as long as it could connect to my plane.

What I Need To Do

So: back to my list of things to do. The first was “connect to my plane, right?”

My list:

  1. Connect to the AeroScout to validate the TX16S -> Spektrum receiver connection
  2. Set up a throttle cut (to allow me to carry the AeroScout safely while powered up; a throttle cut prevents the prop from being activated)
  3. Set up flight modes for the Spektrum
  4. Set up panic mode for the Spektrum

Connect to the AeroScout/Spektrum

This is the first thing I did after unboxing the TX16S, and it went flawlessly, for the most part, except I didn’t have the throttle cut set up; without that, I’m not comfortable using the radio with the plane. So after “binding” my radio to the plane – a basic requirement, because it means I can communicate with the plane – I needed to set up at least one safety feature before I could take the controller and plane to the airfield.

Throttle Cut

The throttle cut was (and is) really important; it’s the first lesson of safety with RC planes. You don’t power up the plane without having your radio on, and you don’t engage the prop until you’re ready to actually fly. The RC engines (and their props) are fast and sharp; you don’t want to injure yourself by accidentally applying the throttle while you’re carrying the plane to the airstrip.

Flight Modes

The flight modes are a little more interesting. One of the really attractive features of the Spektrum receivers is that they support flight modes like “beginner,” “intermediate,” and “expert”.

In “basic” mode, the plane keeps itself relatively level, and the flight controls are limited; you can fly, but your controls are dampened, which prevents you from doing crazy (wrong) things, and also keeps the plane from generally going out of control. It’ll stay relatively level and turn relatively gently. You’re telling the plane what you want to do, and it more or less does it.

In “intermediate” mode, well, you’re still dampened, but not as much; you are flying more than you are with basic mode, and can lose control more easily, but it’s still dampened somewhat.

In “expert” mode, there are no dampeners, there are no controls, there’s nothing keeping you “relatively level,” and you’re literally controlling everything the plane does. You’re not “protected” from your inexperience in the slightest; this is the acrobatic, real flying mode, and is what the old-timers like my father would have thought was actually flying RC; they didn’t have those newfangled protection modes!

The AeroScout is very literally my first plane (and only plane, so far). I have maybe ten or twelve flights with it; I am still at “rank beginner” in skill, although I’m proud to say that I try to fly “intermediate only” when I’m using the Spektrum controller, to improve my skills.

With the TX16S, though, one of my goals is to figure out how to get it to support those Spektrum modes, not because I want to target them, but because I’m not good enough not to target them yet! One of the nicest things about the modes is, after all, to fly intermediate and get yourself in a pickle, and switch the mode to “safe” mode and have the plane level itself out for you – it rescues you, and that rescues the plane, and protects your investment in it.

Panic Mode

The “panic” mode is similar; I’d like to be able to flip a switch and have the plane stay in the same “flight mode” (assuming I can get that set up) but still level itself off and normalize position; imagine I get my plane in a spin, I want to be able to hit a button and have it level itself off (rescuing me from the spin) and then resume flying.

Actually Setting It Up

Unboxing went pretty well. I ordered a battery with the radio; slotting it was pretty clear enough, although the manual that came with the radio was very limited on information. The radio has two USB-C ports (why?!) and hides a micro-SD card under the bottom rubber bumper. It’s built pretty solidly, though, albeit out of plastic.

The bottom USB-C port is for charging; the top one is for communication, so if you’re connecting the radio to a computer as a USB device, you use the top port, and if you’re charging the battery, you use the bottom USB-C port. This is a design decision that is unclear to me; I’m pretty sure it’s related to design choices for the radio and how it’s put together in two panels, but ideally you’d have one slot and use it for everything the radio needs to communicate.

The SD card slot is workable, but it’s not mounted perfectly; it’s painfully easy to put an SD card in place and miss the slot, which means you’d have to open the radio to get the card back out. In general, if you’re working on the SD card (which is how you’d update the radio or work with the radio data directly) you’re probably better off mounting the radio as a USB storage device (the top USB-C slot) and working with the filesystem that way.

Binding to the AeroScout was, as I’ve said, really pretty easy; in EdgeTX 2.7.1 (the version that came with the radio, remember?) you’d go to models, create new, and the main thing to do was select the communication protocol (DSM) and hit the “bind” button. Once you’ve done that, you’d power up the AeroScout and tell the receiver (an AR631 in my case) to bind; it has a convenient physical button on the receiver for that purpose. Once the bind process is done, you can actually control the plane with the radio. As I’ve said, though, there’re no safety features at this point.

I tried a few different ways to set up the throttle cut. Most of the available tutorials and documentation focuses on OpenTX and not EdgeTX; they are different! The features are generally compatible, but the locations of things and how you’d set them are not the same.

One thing I did while trying to work out the throttle cut: update EdgeTX to 2.8.0, as the reference materials keep using the “current version.” This was relatively easy – put the updated binary on the radio, tell the radio to prepare to flash the new firmware, then boot the radio while holding the trim switches “in” – and the new EdgeTX had some features that it rather wanted, like support for a period (“.”) in the on-screen keyboard. I found a video for this online; it was not part of the supplied documentation. The video had information that I had not seen elsewhere, an issue that EdgeTX (and the radios) suffer routinely.

I got the throttle cut worked out with Open TX Ultimate Arm Switch; I want to change one thing about this, because the switch that it uses starts in the “down” position and the disarm switch ends up being the “up” position (i.e., I want to invert the disarm as given by the tutorial). But it works, so now I’m able to at least take the radio to the airfield without worrying about a very very very basic safety rule.

The “beginner,” “intermediate,” and “expert” flight modes – and the panic button – I still haven’t figured out.

The biggest problem EdgeTX has – and OpenTX shares it – is a lack of documentation. It’s moving relatively quickly, and there’s not a cure for that (nor is it really a problem) but the community is still a little on the early Linux “do it yourself” curve; Spektrum receivers, for example, are (from what I’ve seen) really popular, and I’d think that “here’s how to set up your Spektrum to match features with the Spektrum transmitters” would be a huge lever for EdgeTX… and it’s just not there.

Binding to Spektrum is, but as long as you can support the DSM protocol, that part’s pretty easy. It’s the other features that should be normalized; there could be (and should be) a reference somewhere that says “oh, you just got your [radio here] and it’s running EdgeTX? Here’s how to connect to [popular receiver] and configure the radio to use [reason the receiver is popular].”

The receivers are fairly generalized; some have special features (like many of the Spektrum receivers!) and the radios are generally the same as well (which is why EdgeTX can run on so many of them); the specialization for the radio and receiver combinations would be pretty light, pretty much a matrix of “if your radio can support DSM, you can connect to Spektrum like so and configure these features by following this howto…”

… and if I learn the radio well enough to do that for the RadioMaster TX16S and the Spektrum receivers, that’s what I’m going to do.

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