APM2 and Rx All-in-One!
As most of you may or may not know, I've been a big proponent of using PPM Sum (aka CPPM) with the Ardupilot since I first figured out how to make it work. The simplicity of just running a single wire from the Rx to the APM is very attractive. It eliminates 7 possible failure modes (losing the wire connecting channels 2-8) which could result in loss of control. There's only 1 wire to get right, but also one wire to get wrong. Fortunately, the APM can handle complete loss of signal well, and if you set your failsafe to handle complete signal loss, all is good.
I was using this on my HK450GT FBL helicopter, along with a FrSky D8R-SP Rx. Again, as anybody who knows me is aware, I'm a big fan of FrSky radio equipment. It is affordable, and high performance offering true diversity on the Rx, easy to use CPPM (just requires a jumper on two pins), the Rx is very tolerant of low voltage (it'll keep going LONG after the APM would have shut down, down below 3V). And rebooting and reacquiring the Tx signal takes less than 1 second.
All of these features are superior to the big name brands, Futaba, Spektrum, etc.
And the telemetry features offered by FrSky is just the icing on the cake. RSSI (signal strength), Rx voltage, external voltage (flight battery), and even the option for a telemetry hub with all kinds of goodies This is somewhat negated by using an APM, but still, you can put one of these on your Tx and have all the info right at your fingertips.
Anyway, back to my little 450 heli with a HUGE Rx mounted on it, the D8R-SP.
I discovered that FrSky offer a new Rx, the D4Fr which is a small, yet full-range Rx. And while it only has 4 channels out, it can be configured to do 8-channel CPPM with the simple addition of a jumper! Brilliant, and there's no reason why any modern compact receiver shouldn't be able to do this. This Rx does not have as many telemetry features as it's big brother. It can only report RSSI and Rx Voltage, it does not have connectors for the telemetry hub or external voltage. But that's fine, as the APM can be used to report voltage anyway. So I ordered one and it arrived Friday.
I started working on setting it up, when the wheels started turning in my brain. The "case" is just a flimsy plastic thing, almost useless anyway. And I'm only going to have a single cable going from the Rx to the APM, and it's so small. And the APM2 has those stand-off pins onto which the daughterboard is soldered. And those pins are kinda long... And I've got this piece of empty prototype board sitting around...
Pretty soon I had de-cased the Rx and stripped all the input pins off the APM2.
I soldered the proto-board to the daughter board standoffs, and then glued the Rx board onto the proto-board. I soldered jumpers on both the Rx and APM2 in order to set both into CPPM mode. And then I soldered a jumper wire for the CPPM signal, power and ground. Done.
The complete unit is compact. There's no wires to get in the way of whatever vibration-damping mount you are using. There are no wires to come disconnected. I suspect this setup is at least an order of magnitude more reliable than a standard 8-channel APM2 setup.
Even better, it's compact, and easy to move between vehicles.
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Developer Comment by R_Lefebvre on June 9, 2012 at 8:05pm -
@Jack, I've got all the open source I can handle already. I need at least one thing to "just work". ;)
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Comment by bbberrey on June 9, 2012 at 8:06pm -
If your looking for Telemetry try the v2 of the receiver, I have used in the past a few of the D4FR, and i just found that the version II that supports one analog and a connection to the standard sensor hub also, take a look. (this is the best US supplier, quick, cheap, and very helpful http://www.alofthobbies.com/frsky-d4r-ii.html
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Comment by Carl La France on June 9, 2012 at 9:14pm -
Genius !Good Post! What I like is you guys have dealt with this stuff so much you just have to look at it and you know if it will work or not and are not afraid to cut into a circuit board for the betterment of the product for your own use I have been pricing some of the stuff for my own set up it is not cheap.I have been following along slowly gathering knowledge I learn something new every day when I turn on the computer
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Comment by CharlieNoFun on June 9, 2012 at 10:47pm -
I just ordered from aloft! Thanks for posting bbberrey. I had been waiting till my next HK order but those prices are almost the same and I'm sure I will receive it much sooner. Excited!!
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Moderator Comment by Gary Mortimer on June 10, 2012 at 12:20am -
The missing link, well done that is a top idea. Especially as I already have some FRSKY gear heading my way to try!
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Comment by Chris Huitema on June 10, 2012 at 12:41am -
I have just re-flashed my D8R-ii PLUS to the CPPM flie found on this page (beta test section)
http://www.frsky-rc.com/download.asp?id=23
took me a while to find that hidden page (not really hidden, but not obvious)
Cant find alot of info on it, but from what i've seen it will output CPPM on ch8.
Now to set the APM to PPM mode!
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Comment by Daniel Chapelat on June 10, 2012 at 1:36am -
Hello
This arrangement is it possible with ArduPilot Mega 2560 Complete kit? if so is it possible to have the schematic? thank you cordially Daniel
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Comment by Chris Huitema on June 10, 2012 at 1:48am
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Wow, that was easy! already set up for it..
Just short pins 2 and 3 :)
This is the setup needed to flash the RX with the PPM firmware. the USB adaptor came with the TX RX combo, i had to made the adaptor with the RC connector, nothing to it really.
Cables, Before and After, massive space saving!
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Comment by Veikko Vierola on June 10, 2012 at 2:38am -
How about Futaba S-Bus integration to APM2?
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Comment by Lyn Rees on June 10, 2012 at 3:40am
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Have not done any extensive research but, should also be easy to use the Flytron Open LRS (already in open circuit board form) Just jumper two pins for serial output!
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