Model questions from a 'newby'

I received my Devo 10 Tx just a couple weeks ago, and installed Deviation 4 just now.

I then went searching for model definitions for the aircraft I fly, to start learning about effective use of these things. I found one guy in particular, Tom Z, has created a large number of model files covering just about every aircraft I will be flying with this. Thanks Tom!

However, I am not content with just using another's work. I want to understand everything I see in these model files. As an ancient software engineer, I found it easy to explore the interface provided by Deviation, and can see what is available to be changed and how to change it. What I have not yet found is a guide as to what values to use, or explanation as to why one would choose one value over another possibly acceptable value. And there are some terms that I need explained. For example, until I received my Blade 120 SR, I had no idea what a swash plate is (I do now, though, as a guy in the rcgroups 120SR forum explained it for me). On several of my Tx, I see a gear switch, but it looks nothing like a gear. I have no idea what it is normally used for. There is a mix switch, 3 positions, but what is mixed? I also see an fmod switch (three position), which I would assume is to allow one to select among Angle, horizon and acro mode on aircraft that use the MultiWii FC (and related products), or the low angle stability, high angle stability and agility modes on most Blade quadcopters. Is that right? And, I see two position switches for rudder, aileron and elevator, each with the string 'D/R' following the name, but I do not know what the 'D/R' signifies or why these switches would be needed.

On my Spektrum DX5e, I see a rate switch, 2 position, that lets me select low rates or high rates; and my blade quads are easier to fly with low rates selected. But I see no rate switch on the Devo 10.

Let me ask a generic question or two.
1) I see a number of model files in the model directory, but none have a model name in it`s contents. Is the model name that would appear in the Deviation taken from the file name? If so, should I assume that the model name is restricted to 8 characters? If not, what is the format in the model files for specifying a name (if I want to provide a name within the file), or do I have to assign model names using the Deviation user interface?
2)I see only 30 model files. Am I limited to 30 model files? If not, what is the maximum number of models?
3) Is there documentation of the file format for the model files, to which I can refer if I want to edit the contents of the files using Emacs (my favourite programmer's editor)

Where can I find reading material regarding the why of model definition? That is, the manual does a decent job of explaining what can be changed and how to change it, but not so much on why it could or should be changed.

Finally, I noticed Tom Z created different model files for ultra beginners, beginners, standard model, and often 3D models (thanks again Tom). While it would be trivial for me to identify what is different between the different files for the same aircraft, what I need to be able to discover is what those differences imply for how the aircraft flies, and how to decide when to switch from the one to the next based on improvements I see in my ability to fly; as I work through various exercises in my attempts to learn to fly better.

I guess that is it for now. I am sure I will have more questions when the modules I ordered arrive, and I have to install them.

I will appreciate any information provided.

Thanks

Ted

First part.


Ok, lets start from the beginning and crate some sort a crash course in R/C lingo.

1. Channel

Protocols have channels as discrete units of transmitting values (digitally nowadays) from your transmitter to the receiver. Channels are transmitted in packets, and packets have some sort of a periodicity, depending on protocol.

Now, you can simply see channels as numbers 1,2,3,4...etc or you can (and here it will depend on the protocol) see channels associated with thei use on the model.

Example, DSMX:

Channel 1 -> used for throttle
Channel 2 -> used for aileron
...
Channel 5 -> used for gear
Channel 6 -> used as AUX1
Channel 7 -> used as AUX2

What you see above are just conventions, and sometimes they not even true between different transmitter models of the same manufacturer.

Deviation is capable of mapping channels in a model configuration depending on protocol, so you get the correct channel assignment on the receiver, if you respect the labeling.

2. Switches

Switches, being binary (0/1, on/off), three position (0/1/2, low/mid/high, -1/0/1) or analogic (pots) are means of altering the channel output. You can tie a switch to a channel and modify the final value of that channel that's being sent to the receiver to you liking. See below, mixes.

Switch names don't matter, other manufacturers use identifiers such as Switch A, B, C and so on to label switches. Use the switches as you see fit, it doesn't matter.

Deviation being the flexible firmware that it is, imposes no convention on the user like 'normal' firmwares do, so as far as I care use the FMOD switch to turn on and change color of your LEDs.

3. Mixes / Mixers

These are simple programs that take an input value (a stick movement or a switch position) and output a certain value (which of course ca vary in time).

Probably this is best with an pseudocode example:

input = THR ; throttle stick
scale = 0.5 ; channel properties, scaling, 50%
output = input * scale

when SW_GEAR == 1 ;
scale = 1
output = input * scale ; mix_type = replace, current value is discarded

when SW_MIX == 0
value = 10
output = output + value ; mix_type = add, current value is altered
.
.
.
return output ; this gets sent over the air to the receiver

Now, as a programmer, this is the best way to see mixers / mixes, in the end there this state machine which has a number of input and outputs. You alter it with your own rules and that's it.

4. Channel values at receiver (PWM)

This is PWM basically, pulse width modulation. Normal bounds are between 1000us and 2000us, most transmitters and receivers will output 1150us to 1850us with 1500us as center channel. This is what basically having a scale of 100% in channel properties means.

But, of course not all protocols and receivers are created equally, so you will have center channels at 1520us, etc, etc, etc.

PWM output requires a pair of wires for each channel, and this is very common in airplanes, where you do not have any sort of flight controller.

5. Channel values at receiver (PPM)

Some (usually more expensive) receivers can output a steam called CPPM (sum PPM) which basically sequentially encodes (usually 8 yeah that's eigth) channels over a single pair of wires. Very common in multicopters or helicopters.

6. Channel values at receiver (Serial)

Well, not much to say here, values are transmitted over an UART. Needs a counterpart on the flight controller/decoder. Common on multicopters, usually with Spektrum compatible satellites.

7. Channel values over SBUS

No idea here, never used SBUS which is a Futaba thing I think but probably more similar to Serial than others.

Model files without a model name or values are empty.

Deviation does not have the capability to create new files (to save program space) and you need to manually add more modelX.ini if you want more than 30 models.

Limit is 256 IIRC.

You can use whatever editor you wish except notepad (UNIX line ending convention) so your Emacs is fine (vim guy here but whatever).

There was some initiative to have the contents documented but I'm not sure if it was completed or not. You can create/edit a model either in the radio or emulator then examine the model ini's contents.

To add more models, copy model30.ini as model31.ini, model32.ini, etc.

Now lets try and talk about the actual values you can have for a model.

They are model dependent and there no universal recipe. There I said it. Deal with it:)


An example would be 2 planes, one with very large ailerons and one with tiny ailerons. 2 servos would be controlling the surfaces on channels 2 and 7, channel 2 identically configured but with it's value reversed.

Starting with let say 70% channel scaling (for both 2 and 7):

1. Model with large ailerons would mostly need reducing the scaling to about 40% for starters.

2. Model with tiny ailerons would need increasing the value to have any effect in flight.

Plus, everybody has their own flying style, when I like twitchy models someone else like to fly realistically and need reduced values.

Next episode: expo

Ok so EXPO, this is mapping the input of a channel over an exponential curve, in order to have the linear movement of a stick (such as ELE or AIL) less brutal at around center and bigger at extremities.

EXPO can be positive (as above) or negative, where sticks are made more sensitive at around center (Futaba does this the other way I think).

EXPO values in Deviation are not equal to expo values in other firmwares/manufacturers radios, as different curves are implemented.

I use expo mainly to tame down a very twitchy aircraft (see the plane example above) and allow for smoother flight with very small inputs. You will get the feel of this as you progress with your flight skill. A value of around 25% is ok for starters, maybe more if you have no flying skill.

Keep in mind you will need to avoid banging the sticks, as EXPO makes extreme movements _very_ brutal.

And now we interrupt this program with info about flying skill and orientations

So, depending on how cautious your are, and mostly your age it will take from weeks to years to be able to fly without thinking. Like the old fighter pilots would say 'fly by the bottom of your pants'.

The most difficult part of flying is re-wiring your brain to react without thinking to different orientations.

Imagine you aircraft with the tail at you:F is front, B is back, you get the idea.

Now, your stick on your radio won't change, but your aircraft can and will rotate. Your brain will need to adjust and command your fingers to move the sticks the way you want the aircraft to move.

When the aircraft is in the above position, no problem, front is front, back is back, etc.

Now rotate it 180 degrees, so it comes towards you. Suddenly front stick movement becomes back, and back becomes front.

At first it will seem it's impossible to adapt to this, but trust me, keep at it, your brain is a wonderful machine that one day will make things 'click' into place.
You will hear about this click all over the RC forums. Yes, it's real, and it will happen when it will happen. If you're kid, you'll be fine in 1-2 months. If you're in your 30s it will take you about 3-4 months. I don't know what happens when you're older as I haven't got there yet

Anyway, it depends on how much you practice too. Go for it 3-4 hours a day and it will happen sooner obviously.

The only certainty is that it will happen and then your brain will command every stick movement without thinking, naturally. Congratulations, you just moved this process into your unconscious mind. This is the first step.

Next step is to learn program Deviation



(kidding)

Dual Rates

Or multi rates if you will.

This simply signifies that you can have different channel outputs for a single channel depending on external factors, such as stick positions.

Commong example is having a low channel scaling (25%) for mellow easy movements and another 75% (or 100%) sharp scaling for aerobatic maneuvers.


How do you do this in Deviation? Very simple.

1. Choose a channel
2. Choose a switch
3. Change the mix type of the channel to D/R
4. Select first position of the switch (such as GEAR0)
- enter scale as 25%
5. Scroll down, select switch GEAR1
- enter scale as 75%
6. Save


Congratulations you have configured dual rates. Now, whenever your GEAR switch is on the 0 position the channel will have a scaling of 25%, and when on 1 position (down) it will have 75% output.

Multi rates would be having a 3 positions switch with 3 different values for scaling. Or 2 different switches together (that wouldn't be necessary in most real life scenarios though).

Easy huh?