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Old Dec 01, 2012, 07:19 PM
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Walkera DEVO for the 9x TX

I have been flying a Genius CP (DEVO) with a 9x for a few days now and while I probably don't have all the issues worked out I figured it's time to post some information. This will be a continuous work in progress.

BEWARE, the MTC-01 is known to be flaky at times and especially running this nonstandard configuration it could be dangerous. This is for informational purposes only, everything below could be incorrect, don't try this at home.

First a quick start for the impatient:
  • Models created to be used with the MTC-01 should use a 23.5ms frame time with 400us pulse separator length. Do not use more than 8 channels (less is better) and if you're using an old MTC-01 with the original firmware it is a good idea to set any channels you're not using to -100 to help prevent the "channel mixup" issue. Newer MTC-01's don't have this problem.
  • Binding requires first plugging the MTC-01 into your 9x, then turn on the DEVO RX, finally turn on the MTC-01. MTC-01 should have a solid blue light and the DEVO RX should have a flashing light.
  • Next wiggle the stick, switch, or whatever that is on channel 2. The MTC-01's blue light should start flashing. Within a second or two the DEVO RX's light should go solid.
  • Wiggle the stick on channel 2 again. Now the MTC-01's green light should start flashing. Within a second or two the DEVO RX should initialize (on my Genius CP the heli "comes alive" and wiggles the collective at this point).
  • Now you're ready to fly.

Once bound if you do not power off the MTC-01 then it will rebind to the same RX automatically without having to go through the steps above.

Apparently there are two versions of the MTC-01, the new one just being released recently. Lets call these v1 and v2. I do not know what the differences are but there are hardware changes and probably firmware. Supposedly the v2 fixes some issues with failsafe and possibly the "channel mixup" issue. There is also a new firmware for the v1 that fixes the "channel mixup" issue but it's unclear if that actually fixes it or not.

The channel mixup issue is where the MTC-01 will get out of sync with the PPM stream and start transmitting the wrong channels to the receiver. In other words the channel order gets mixed up. Obviously this is very bad and dangerous when flying.

The failsafe issue comes in to play if you disconnect a v1 MTC-01 from your radio while it's still powered on. Apparently it can start sending random channel data like full throttle to your model. If that happens you need to turn off the MTC-01 as fast as you can, this will hopefully send your DEVO RX into its own failsafe mode.

My MTC-01 is a v1 and it also runs the old buggy firmware. This is all I have experience with and is what all my testing has been done with. I would be happy to try a new v2 MTC-01 or upgrade the firmware on mine if someone sends me one of the v2 MTC-01's and/or a DP02 firmware upgrade cable.

Alright, lets get into the details.

The first thing that needs to be done is to connect the MTC-01 to the 9x. The MTC-01 comes with a cable that can be plugged into the 9x's trainer port and this works fine. However, I put my MTC-01 board inside a 9x style TX module. This gives me a little more range because of the better external antenna and I power the MTC-01 from my radio so I never have to worry about its battery. I built a small PCB that has a 3.3V voltage regulator to supply power and connect to the 9x module pins. The audio plug needs to be removed from the board for it to fit in the case. The internal antenna can be removed and coax soldered in for an external antenna. I'm thinking of adding an RF amplifier in there as well to get a power boost and more range.




Once the MTC-01 is connected to the 9x now we need to create a model. I'm using er9x on my 9x which gives great control of everything. Other firmwares may be slightly different or possibly not work at all if they can't be configured properly, let me know.

Some adjustments need to be made to the PPM signal for the MTC-01 to recognize it. The frame length should be no longer than 24ms. I use 23.5ms. The most important setting is the pulse separator length should be 400us. The MTC-01 will also accept 350us but I have had problems with glitching when using that timing. My WK radio actually uses around 423us so I'm not sure how precise this value needs to be. On the v1 with the old firmware my guess is the channel mixup issue is caused by the PPM frame sync pulse not being long enough so if you use too many channels or too many channels have long enough pulses then the MTC-01 goes haywire and loses sync. To avoid problems either run less than 8 channels or with 8 channels I run the longest frame time I can and I set any channels I'm not using to -100 which makes their pulse as short as possible therefore giving a longer sync pulse.

See the quick start above for binding information.

Well, that's it for now! Simple right? Now the hard part, , I will make a follow up post below to describe how I set up my Genius CP to work with my 9x.

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Old Dec 01, 2012, 07:19 PM
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Genius CP setup:

Attached are two er9x models. Note these are a work in progress and not fully tested. The "beginner" model basically uses less throttle in its curves and more expo. These settings are based on some recommendations I found for DEVO radios (here, here, and here). Personally I run much less expo than even the advanced model (around 15% or less even) for more control.

The current gyro sensitivity settings may be incorrect because I believe the DEVO settings are based on a 0 to 100 scale where the 9x is -100 to 100. The current values are 82% and 60% but I believe that it may need to be changed to 64% and 20%. Testing needs to be done.
  • The throttle kill switch does what it is suppose to (-100 throttle and 0 collective pitch to help prevent boom strikes). Once set throttle kill can not be turned off until throttle stick is set to -100 and flight mode is idle down (ID0).
  • ID switch sets the flight mode, ID0 for normal mode idle down, ID1 and ID2 for "stunt" idle up modes.
  • GEAR switch sets the gyro sensitivity, 0/OFF/BACK is high sensitivity strong hold, 1/ON/FORWARD is less hold which helps with certain 3D maneuvers.

The Genius is using a 7 channel RX so you must be in 8 channel mode.

The channels:
  • Channel 1 = Elevator
  • Channel 2 = Aileron (needs to be inverted)
  • Channel 3 = Throttle
  • Channel 4 = Rudder (needs to be inverted)
  • Channel 5 = Nothing (?)
  • Channel 6 = Collective
  • Channel 7 = Gyro sensitivity (?)
  • Channel 8 = Nothing (?)

Do not use a "heli" setup on the 9x with swash mixing, the collective is done on channel 6. Do use the "swash ring" feature at about 80% otherwise the swash can bind.

Gyro sensitivity must be above 0 (on a -100 to 100 scale) otherwise the gyros are turned off. A low gyro value will make the tail have very fast response to stick input but it will not hold as well. A high gyro value will slow the tail down and have a more solid hold. If you go too high then the tail will wag/hunt a lot and not be stable.

When in 3 axis mode after binding make sure you have a solid green light on the Genius RX board. If not then that means you're not sending a gyro sensitivity (channel 7) above 0 and flying like that is near impossible. In 6 axis mode the heli will drift and yaw badly if this gyro sensitivity setting is not transmitted. I have no idea how this transmitted gyro sensitivity interacts with the gyro sensitivity pots on the RX board (anyone know?).

Be careful about trim settings when doing the bind. Apparently the Genius RX will (sometimes? always?) remember some of these values (elevator, aileron, and rudder it seems) and offset the channels by whatever trim you had set during bind which essentially removes the trim or makes the trim too much or other adverse effects. In fact if you don't send anything on channel 7 (for example you can use only 6 channels) then it's possible to set up the trims in such a way while binding that the heli will sort of fly nicely in 6 axis mode without channel 7 (I don't recommend this though). It's weird, I haven't quite figured out how it works.

Wow, it seems so simple now after all that I learned then writing this down. It was a real struggle for a while. Especially figuring out channel 7, before that I thought the GCP really sucked. It took lots of broken parts to bring this to you so feel free to send Genius CP blades, canopy, frame, etc.
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Old Dec 02, 2012, 09:42 AM
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Sweet job LittleMo. Thanks for sharing!
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Old Dec 02, 2012, 09:51 AM
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That is a lot of work!

Just need video of your flying skill lol
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Old Dec 02, 2012, 09:56 AM
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Now sad that I missed the $69 and $89 deals for the Genius CP and Mini CP over at WOW during their Black Friday sale.

I see that BangGood sells the MTC-01 for only $18.

I wonder if it's the V1 or V2?
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Old Dec 02, 2012, 10:15 AM
Ain't crashing often anymore
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WOW - thanks for the invitation - I feel honored!
It could be a stepstone to: One TX to rule them all
-mike-
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Old Dec 02, 2012, 10:35 AM
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Thanks!

I really like working with er9x because it seems possible to do almost anything.

Yeah my flying skills aren't anything really since this is my first CP heli. I might do a video just to prove that a 9x can fly a Devo though, I'm waiting for my camera from China. I did get my Genius from WOW on Black Friday although I had already been working with the MTC-01 for while previously so I had I pretty good idea that I could get it to work.

It's doubtful that BG is selling the V2 MTC-01 yet unless they go through stock like crazy, I got my first MTC-01 from them in September. I'm not even sure if the V2 is out on the market anywhere yet. Plus, it may not really be necessary to get a v2 as I haven't had any problems in a while (since I figured out the frame timing an such). Given a choice though, I'd probably go with the v2 or at least a MTC with the new firmware (these are untested with the 9x though, hopefully it still works).
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Old Dec 02, 2012, 12:01 PM
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I just spent some time outside flying through all the modes, I don't know if they're the best settings but everything seems to work. Switching flight modes is seamless.

Still not sure about the gyro setting, it doesn't seem to do much of anything when I change modes.

5 minutes flight time with stock 200 mAh batteries. 8 minutes with 300 mAh nano-tech's. Seems pretty consistent regardless of flight mode.
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Old Dec 02, 2012, 01:18 PM
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Nice, have you shared the results with the 9x Forum guys? Perhaps they can implement the proper pulse separator length on future er9x releases. I know they were interested in getting Devo support in the past.

Have you checked to see if the MTC-01 has the flashing plugs on them?
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Old Dec 02, 2012, 01:52 PM
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Quote:
Originally Posted by Daryoon View Post
Nice, have you shared the results with the 9x Forum guys? Perhaps they can implement the proper pulse separator length on future er9x releases. I know they were interested in getting Devo support in the past.

Have you checked to see if the MTC-01 has the flashing plugs on them?
Yeah, I posted over there a while ago. I actually had a bit of a log going as I tried a whole bunch of stuff to get it working. Eventually once I figured everything out I went back and deleted most of those posts because they had all kinds of crazy ideas that didn't work. I need to link back from there to this post because this one has all my latest results.

It is possible to use exactly 423us(*) if you use eepe to edit the model. I'm not sure it makes a difference though. I have now at least a dozen flights with no issues whatsoever with the models posted.

Yes the MTC-01 has the plugs to flash it. It's a simple serial interface on the MTC-01 but Walkera encrypted everything and the DP02 itself provides some sort of non-trivial interface that is used to flash the firmware. Totally ridiculous and it means you need a DP02 interface to flash it. The DP02 itself costs more than the MTC-01 so...

Edit:
(*) Sorry, I thought it would because it lets you type it in but no eepe won't let you set it to odd values either. 400us does seem to work fine though.
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Old Dec 02, 2012, 04:56 PM
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Updated the Genius CP models to version 2. These now have a "sticky" throttle kill so that once the throttle is killed it will not turn back on until throttle stick is all the way down and flight mode is back to idle down.
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Old Dec 03, 2012, 05:55 AM
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Quote:
Originally Posted by LittleMo View Post
Some adjustments need to be made to the PPM signal for the MTC-01 to recognize it. The frame length should be no longer than 24ms. I use 23.5ms. The most important setting is the pulse separator length should be 400us. The MTC-01 will also accept 350us but I have had problems with glitching when using that timing. My WK radio actually uses around 423us so I'm not sure how precise this value needs to be.
Is the MTC-01 is compatible with the PPM signal on the trainer port of a Futaba transmitter? I don't have a oscilloscope yet to to measure frame length and pulse separator, but maybe someone already knows?
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Old Dec 03, 2012, 06:11 AM
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Quote:
Originally Posted by compie View Post
Is the MTC-01 is compatible with the PPM signal on the trainer port of a Futaba transmitter? I don't have a oscilloscope yet to to measure frame length and pulse separator, but maybe someone already knows?
It might depend on the radio. According to this page some Futaba use 0 to battery voltage (wow!) while others use 0 to 3.3 volts.

I believe wy WK radio actually outputs around 0 to 1 volt so I'm not even sure if 3.3 volt is safe but I have been using it OK so far.

The frame timing might depend on the radio as well so measuring it may be the only way to know unless the Futaba firmware lets you adjust it.

If you have an Arduino or other avr device I wrote a sketch that will measure the PPM signal. That's how I do my measurements. It's actually easier than an oscilloscope because it just gives me the values. I have attached it here. It uses PD2 as the input, of course that can be easily changed in the code. You do still have to make sure the output of your radio doesn't exceed the Arduino's voltage.
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Old Dec 03, 2012, 06:48 AM
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Very nice LittleMo, I will keep an eye on this thread for sure!!!
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Old Dec 03, 2012, 08:21 AM
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I just updated the Genius CP models to v3 with much better pitch curves. I found this where they did detailed tests to find maximum thrust and that is where I set the maximum pitch just above. I also made some changes to make the pitch response much more linear.

My flight time has gone way up. Could be because of the motor breaking in or maybe because I'm no longer switching between a bunch of modes testing things. Using idle-up for the whole session I'm at 6 minutes on the stock batteries and almost 10 minutes (!) on the nano-tech's (have to watch your motor temps if running this long; it's reasonably cool outside and my motor barely gets warm).
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