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Author Topic: How I Programmed Elevons for a DLG with a Deviation Firmware TX (Devo, Jumper)  (Read 661 times)
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vtdiy
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« on: December 26, 2018, 10:32:48 AM »

I recently bought a Walkera Devo 7e transmitter, and added Deviation firmware so it could be used under DSM2 -- specifically to power Lemon Rx receivers and various manufacturer's bricks in the planes I build.

I'm not a helicopter pilot, and though the primary emphasis in the firmware (and of course the TX itself) has been heli oriented, I wanted to see if there were complex control advantages in this system over my older Spektrum DX6i for fixed wing aircraft.

I chose the Devo 7e Tx because of its low cost -- $59 delivered from an Ebay seller. One advantage I knew I'd appreciate without even trying it out was the 30 model storage capability -- I'm an avid builder and I'd already run out of models on the DX6i, so having the capability of building and flying 30 more was great! (More recent versions of the Deviation firmware apparently allow up to 200 models -- I'm still using Version 4.)

I found that setting up a DLG flying wing with elevons on the Devo 7e is not nearly as simple as doing the same thing on the Spektrum DX6i -- though the programming possibilities are undoubtedly more flexible. It took a lot of trial and error to figure it out, so I thought I'd pass on what I learned in case it helps anyone else. I'm going to break this process up into separate posts as learning steps to make it somewhat easier to absorb.

I hope this info will be applicable to other transmitters that use Deviation firmware, like the Jumper brand, and possibly others.
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vtdiy
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« Reply #1 on: December 26, 2018, 10:41:45 AM »

The first thing to understand about Deviation firmware user interface is that it is channel oriented, not control oriented, or aircraft oriented.

What does this mean?

Well I can only explain it by comparison with the DX6i. With that transmitter, if I wanted to program a plane to have elevons, I would navigate to a Tx screen called "Wing Tail Mix" and activate "elevons." This would have the effect of mixing the elevator and aileron channels (DSM2 ch 2 and 3) to which the two elevon servos are attached.

(I should mention here that my old Spektrum DX6i had a bug in its firmware for the elevon mix -- requiring a workaround -- but that's an anomaly and isn't the subject here.)

Under Deviation firmware on the 7e to do the same thing under its channel oriented philosophy, I would first set up channel 2 to have two "sources" : "ELE" and "AIL". (A source in Deviation refers to an input -- in other words, in this case the "ELE" and "AIL" sticks).

And then I would also set up channel 3 to have the same two sources. Now channels 2 and 3 (the two elevon servos) are both  controlled by two sources (the two individual stick movements).

I will still have to switch servo plugs around, and possibly reverse the direction of one or both servos to get the elevons to move in the correct direction for various stick movements, but this also holds true for the Spektrum DX6i. It's dependent on how the servos were physically mounted in the plane.
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vtdiy
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« Reply #2 on: December 26, 2018, 10:47:40 AM »

To clarify the channel numbering above and stick configuration, as it can be a confusing subject, I am using a transmitter set up as Mode 2. This means that the left stick vertical is throttle, left stick horizontal is rudder, right stick vertical is elevator, and right stick horizontal is aileron.

And the channel assignments I'm using (conventionally marked on the Lemon-RX receiver) are: 1=throttle, 2=aileron, 3=elevator, 4= rudder, 5=gear, and 6=aux.

The naming and channel numbering scheme I am using below is based on that setup.
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vtdiy
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« Reply #3 on: December 26, 2018, 10:52:22 AM »

One aspect of the Deviation firmware that is very useful is the ability to plug in a cable between your computer and the Transmitter and save a model's setup. Or edit it there. It also makes it possible to show the setup here so you can see what is going on. The model setup file is called a "model.ini" and it is a simple text file that you can open, and read or edit in a text editor..

Here is an opened example of a model.ini file that we will be using for our flying wing, showing a simple elevon setup:

[channel2]
template=complex

[mixer]
src=AIL
dest=Ch2

[mixer]
src=!ELE
dest=Ch2
muxtype=add

[channel3]
template=complex

[mixer]
src=ELE
dest=Ch3

[mixer]
src=AIL
dest=Ch3
muxtype=add
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vtdiy
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« Reply #4 on: December 26, 2018, 10:56:29 AM »

 Deciphering the above:

I am using the "complex" user interface for these two channels, as opposed to the "simple" template (more like the DX6i setup -- but only applicable to helis).

Channel 2 has two "pages" of mixers (located directly underneath its heading) -- one mixes the AIL stick to channel 2, and the other mixes the ELE stick to channel 2.

The exclamation mark in front of the ELE means I have reversed that particular source (input) and hence the servo direction. There are other ways to reverse a direction, but that's the one shown here.

Channel 3 is similar throughout, with the exception that ELE is not reversed.

With this setup all my servos ran in the correct direction for all aileron and elevator stick movements.
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vtdiy
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« Reply #5 on: December 26, 2018, 10:59:46 AM »

The next thing I wanted for my flying wing was to change the rates for pitch and roll. Initial testing of the plane showed that the rates, as set up needed to be reduced quite a bit.

Adjusting the roll rate to 40% and the pitch rate to 35% can be accomplished on the DX6i by navigating to the "D/R & Expo" screen and setting them directly for "Aile"and "Elev".

In the model.ini under deviation firmware these rates would look like this when applied to our flying wing:

[channel2]
template=complex

[mixer]
src=AIL
dest=Ch2
scalar=40

[mixer]
src=!ELE
dest=Ch2
scalar=35
muxtype=add

[channel3]
template=complex

[mixer]
src=ELE
dest=Ch3
scalar=35

[mixer]
src=AIL
dest=Ch3
scalar=40
muxtype=add
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vtdiy
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« Reply #6 on: December 26, 2018, 11:13:14 AM »

The next thing I want is a switched in up pitch of 15 after launch -- in glide mode. In a hand launched glider like mine, the launch setting works better at a lower pitch than the glide setting.

The Devo 7e has two toggle switches -- the left one is convenient for hand launching and that switch is labeled "HOLD" In Deviation firmware, the two positions for that switch are called HOLD0 and HOLD1.

To make this a trim setting switch I needed to add two more mixer "pages" to each of the two channels. I've bolded the switch and offset entries below to make them easier to find. As you can see, there are now 4 mixer pages for each channel.

[channel2]
template=complex

[mixer]
src=AIL
dest=Ch2
scalar=40

[mixer]
src=!ELE
dest=Ch2
scalar=35
muxtype=add

[mixer]
src=AIL
dest=Ch2
switch=HOLD1
scalar=40

[mixer]
src=!ELE
dest=Ch2
switch=HOLD1
scalar=35
offset=15
muxtype=add


[channel3]
template=complex

[mixer]
src=ELE
dest=Ch3
scalar=35

[mixer]
src=AIL
dest=Ch3
scalar=40
muxtype=add

[mixer]
src=ELE
dest=Ch3
switch=HOLD1
scalar=35
offset=-15

[mixer]
src=AIL
dest=Ch3
switch=HOLD1
scalar=40
muxtype=add


The above is a manipulation of the model.ini on a computer.

Making changes to a setup like this in the field isn't simple. For instance if I wanted to increase the elevator deflection to 16 while testing a new model using the transmitter UI I would have to:

1.) Navigate to one mixer page out of 4 for channel 2 and change the offset value.
2.) Then save that value and navigate to channel 3, then to its appropriate mixer out of its 4
3.) Then change that offset and save it.
4.) Also note that one value is negative and one positive because of the servo setup -- and this must be maintained.

The equivalent operation on a Spektrum DX6i would be to use the FLAPS switch and set an elevator up trim for that switch.

A much simpler operation since the value is set in only one place, and can be changed on the fly. The Spektrum does not require saving a setting for it to become active. It also automatically compensates for the elevator servo reversal. With the Spektrum, you can leave the flaps screen open on the Tx and incrementally change the value while tossing the model -- it's a quick way to tune a new plane's performance.

While the Deviation firmware is much more flexible, changing things on the fly is more difficult and it's easier to create mistakes in entry. This may have changed in more recent versions of the firmware, but I haven't tried it yet.
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vtdiy
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« Reply #7 on: December 27, 2018, 05:39:01 PM »

The next thing I wanted to add was some expo. I decided to give the roll control 15% and the pitch 35%

Deviation software can accept quite a few different control curves -- I specified expo as the curve You can also set the amount of expo both above and below the neutral control position. So in the mixes listed below, "15,15" means that both upper and lower expo curves are set to 15%.

At present, I'm not switching expo in or out with a switch. Nevertheless all 8 mixers need the curve specified.

I don't think it's possible in Deviation to assign expo for a control once without assigning it explicitly also to every switch mix for that channel, even if there is no change when the switch is active. I'm not sure on that point -- would appreciate any suggestions to simplify.

Here's what the relevant section of the model.ini now looks like:


[channel2]
template=complex

[mixer]
src=AIL
dest=Ch2
scalar=40
curvetype=expo
points=15,15

[mixer]
src=!ELE
dest=Ch2
scalar=35
muxtype=add
curvetype=expo
points=35,35

[mixer]
src=AIL
dest=Ch2
switch=HOLD1
scalar=40
curvetype=expo
points=15,15

[mixer]
src=!ELE
dest=Ch2
switch=HOLD1
scalar=35
offset=14
muxtype=add
curvetype=expo
points=35,35

[channel3]
template=complex

[mixer]
src=ELE
dest=Ch3
scalar=35
curvetype=expo
points=35,35

[mixer]
src=AIL
dest=Ch3
scalar=40
muxtype=add
curvetype=expo
points=15,15

[mixer]
src=ELE
dest=Ch3
switch=HOLD1
scalar=35
offset=-14
curvetype=expo
points=35,35

[mixer]
src=AIL
dest=Ch3
switch=HOLD1
scalar=40
muxtype=add
curvetype=expo
points=15,15
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steveair2
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« Reply #8 on: December 29, 2018, 08:14:50 AM »

Thanks for all the good information.  I could have never figured out how to do all that.
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vtdiy
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« Reply #9 on: December 29, 2018, 10:04:17 AM »

You're welcome Steveair, I saw your comment in another thread about trying to learn how to do elevons with this kind of firmware, and so added this thread hoping it would help.

It's not simple doing elevons in Deviation, though it does get easier with practice, like anything else. You may find that simply copying and pasting one of the above programs into a model.ini with a text editor, like Notepad will get you far enough along, not to have to do much except change a few values. Treat it as a template. I'm assuming your TX allows you to connect to a laptop via a USB cable and upload or download Model.ini's.

If you have any other questions or problems, post them here and I'll try to help.

And as I say, I only have an older version of Deviation software, so some of this may be simpler, now. (Or harder -- I hope not!)
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