
OpenTX is open source firmware for RC radio transmitters - zdw
http://www.open-tx.org
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pserwylo
For those of you interested in what might be a slightly lower level approach:
I saw a talk from Andrew Trigell (of Samba/rsync fame) at linux.conf.au. In
it, he was bemoaning the lack of Open Source firmware for radio transmitters,
while pondering a UAV project hey were working on.

So, in typical tridge fashion, he and his friends created some, and given it
is relatively simplistic, and the transmitters are quite tiny, the feature set
seems pretty impressive (though I haven't had a need to use it... yet):

[https://code.google.com/p/ardupilot-
mega/wiki/3DRadio](https://code.google.com/p/ardupilot-mega/wiki/3DRadio)

~~~
axman6
Tridge also happily uses an earlier version of OpenTX called er9x I believe.
I've worked with him on a bit of the firmware you're talking about here, but
it's not the same stuff. The most impressive thing about the SiK firmware
you're talking about is the stupid range you can get from them on a good day;
line of sight can be tens of kilometers (say 40+), and could potentially be
used to communicate with satellites, all while using a max of 5W transmit
power at 900MHz. There's plenty of more info on both the CanberraUAV and 3D
Robotics blogs from him and others about both these topics. The following talk
as LCA was about such satellites, and there was some talk about using these
radios for these open source satellites.

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jevinskie
I wondered what this exactly was and it is what it sounds like. An open source
firmware for the "box with joysticks" that you use to control miniature hobby
model vehicles (or whatever else you want :).

Firmware running on device:
[https://lh6.googleusercontent.com/Z6Q2WtT2dhpgvCyrq4KEIDH0sd...](https://lh6.googleusercontent.com/Z6Q2WtT2dhpgvCyrq4KEIDH0sd1FUEMcUGk_Av77aIzabDUBBfnBIK0PwAdIjsY04N7uq8EwRKAY3NjVTj0gUc-
qZKItAU-D2JgKwOLZfmgRGXS1dp8dzxCDYsZog4ATRw)

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bananas
Firmware?! Last one of these I built had a simple multivibrator and a 4017
plugged into the RF front end which was pretty simple as well - just a crystal
osc, mixer and antenna tuning and that was it. That was good for a 6 chan TX
at least with a quarter mile range.

I know that's a neck beard comment but have things really got that complicated
that computational power is required? I can understand mixing for helicopters
but not much else.

There is some elegance left in simple solutions.

~~~
pedrocr
>I know that's a neck beard comment but have things really got that
complicated that computational power is required? I can understand mixing for
helicopters but not much else.

Mixing is needed for pretty much anything and it sure as hell beats mechanical
setup. For anything of even medium complexity it's a must. For example in a
simple three channel glider (aileron, rudder, elevator) it's so much easier to
just have 4 servos (1 on each aileron in each wing) and then do the aileron
mixing in software. Otherwise you'll have to arrange the linkage geometry to
get differential travel in the ailerons (for aerodynamic reasons you want more
up travel than down travel) and then make sure the end points and central trim
are all correct. Much easier to just stick the servos in the wing, set the
linkage roughly and then trim it from a software interface. In the old days
you'd have crazy stuff like left and right servos to reverse the direction of
travel, now it's a software setting away.

And that's a simple example. Still in gliders a competition F3F glider will
need much more mixing. You're basically doing laps between two pylons 100m
apart. The world record is below 30s, so that's 120km/h of average speed
including 9 full U turns. To actually be able to do those fast turns those
gliders will actually move all 6 surfaces (2 ailerons, 2 flaps, 2 V-tails) at
once, dropping the ailerons and flaps to increase the lift of the wing during
the turn and using the V-tails as elevators. Then to land the plane you'll put
it in "butterfly mode" moving the flaps way down and both ailerons up to get
it nice and slow for landing.

R/C airplanes are actually very advanced stuff. The jets and scale stuff will
have complex sequencing for landing gear retract, the gliders will do insane
stuff like do over 800km/h dynamic soaring, so you need to have exponential
mapping between controls and outputs to have precision in the center of the
sticks. So radios have evolved to match those capabilities. Radios have been
mixing for decades now, and have had replaceable firmware for a long time. It
used to be that to get a really flexible radio you'd need to spend 1000$. Now
you can get a cheap Chinese made radio for 100-200$ and put an extremely
flexible open-source firmware on it that will do all the things the high-end
radios do and more. Software is eating the world indeed.

~~~
Loic
I was thinking that 800 km/h was a typo, but no, this is the world record:
[http://en.wikipedia.org/wiki/Dynamic_soaring](http://en.wikipedia.org/wiki/Dynamic_soaring)

This is really impressive.

~~~
pedrocr
Dynamic Soaring is quite impressive. At the world-record speeds they were
having problems because the radar guns they were using (the type police use)
were not picking up the speeds anymore. I think there were only a couple of
particularly good ones (particular specimens not particular models) that were
still able to register something and not easily.

Initially they had issues with planes blowing up mid-air because they were
using hollow-molded planes and as soon as a bit of air got into the seam at
the wing leading-edge it would open the wing in half quite spectacularly.
People tend to stand next to a large rock on the mountain in case they need
some good cover. The DS world-records were done with some custom built, very
large very heavy gliders. There's quite a bit of great engineering in the R/C
hobby.

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philtar
It just blows my mind that something like this exists. Really beautiful how
diverse the world is and how computing snuck its way into every little nook
and cranny.

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lgeek
I like Deviation[0]. It runs on commercial transmitters and the developer
reverse engineered many communication protocols used by proprietary systems
which are now supported (some require adding hardware to your transmitter).

[0] [http://www.deviationtx.com/](http://www.deviationtx.com/)

