GA250 Coax Gyromixer: The Ultimative Boardless Brushless Conversion? - Page 5 - RC Groups
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Aug 11, 2011, 01:29 AM
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Well, for whomsoever is watching this thread I just received my gyros and equipment. Olli, this stuff is amazing. Nice, nice work my friend. I now have some work to do with part of my fleet. Should keep me busy for a few days.

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Aug 11, 2011, 04:33 PM
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So much for a couple of days, I had them all installed by late last night for preliminary testing and a few initiation steps. Olli pmd me also late last night as he had a moment to check in on his vacation as to the few steps or cautions needed before initializing these. My fleet is staring at me waiting.

This is good stuff guys! And for those who want to go with a dual swash flybarless application using this gyro to ingrain into the mix here are a few pics as to the final product. I built the upper swash to have two purposes so their are a few extra tabs left coming out of it for a bell hiller flybar assembly if needed or preferred. The build thread for it is located here. Post 530 for the completed flybarred version, it still shows the old G110 gyro but I will post new pics of the completed install.
And here is the first brushless boardless, dual swash flybarless, OlliW boardless Ga250 mems HH gyro modded, Sk-360 coax. And the larger 450 bodied heli in the background is receiving a similar mod. There are instruction in the same thread on how to build one for 1/4 the cost of a helibaby. I have been waiting on a skytec head for it for well over 4 months. If it goes on much longer I will build my own.
Olli, this couldn't have happened without your help. And sorry for cluttering up your thread with these pics but I am jacked my friend!
Aug 20, 2011, 04:52 PM
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Finally, I have hit a stretch to get started with programming the robbe box. But upon inspection I ran into this as soon as I opened it up to get started with the basic soldering work. I need to know how to test the box before starting now since it has an odor of burnt chip with the gas traces along the edge of the lcd screen side. Keep in mind that with my luck the only defective robbe box ever made will always end up in my hands. I kid you not.

Aug 24, 2011, 12:55 PM
Hey Randy,

that's sad to hear... and a bit odd... I had tested the box before shipping and it was perfectly fine then... and the electronics should be quite robust... at least I connected it to the servo plug incorrectly a couple of times without any problems... could you describe what you have done?... if you connect it to a voltage source it should show something on the display...

Aug 24, 2011, 05:05 PM
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Originally Posted by OlliW
Hey Randy,

that's sad to hear... and a bit odd... I had tested the box before shipping and it was perfectly fine then... and the electronics should be quite robust... at least I connected it to the servo plug incorrectly a couple of times without any problems... could you describe what you have done?... if you connect it to a voltage source it should show something on the display...

I haven't plugged it in yet Olli. I just want to make sure I don't damage anything before I do this with the visual damage it has. I will wait until your vacay is over and we can catch up then.
Aug 25, 2011, 02:52 PM
Hey Randy,

so, I am back...

EDIT: I leave what I wrote originally as it is below, but I think I have - hopefully - good news... I opened the other robbe boxes I have and looked more carefully to the lcd... and I think what you see is just the result of the hand-soldering job some asian people have to do for their living... in one of my boxes there even had been a couple of solder flakes on the black lcd casing... I hence think that what can been seen on your photo is solder smoke or coming with the iron too close to the casing...

Hence, I suggest you just power it and see what's happening. I have no doubt that you are quite familiar with the signals on the servo plug. To power the robbe box just connect the brown cable to ground and the red cable to a voltage equal or larger 5V. For that you could use the servo-output-cable of a ESC, a 2S lipo, the ground and 2S pin on the balancer connector of a 3S, 4S, XS lipo, or what ever other means which is available to you... you also could power the GA250-GM via your ESC and connect the robbe box to the servo plug with the yellow marking. The only thing to pay attention to is that the ground for the robbe box is at the TOP of the servo connector to the right if you look at the box... i.e., there the broun cable is in your photos in the above...

as regards the damage... that's most strange... how did the package looked like when you got it? I though I packed everything securely... can you see any broken glass with the lcd? has the chasing been damaged? you see, I am guessing here for a mechanical damage... I can't see how the lcd electronics could have been damaged... from the scheme of the electronics I find it hard to believe that it could be "burned", for that one would have to connect it to a power source at certain pins... otherwise the electonics appears to be quite safe...

maybe you could provide detailed pictures also of the other sides... to see what the problem could be, i.e., if there is anư other smoked electronics...

also, maybe you just plug it in and see what's happening....

anyhow... as unexplainable as it may be, if there is a damage this would be most sad since I would not know a fast and cheap solution which I could offer... it's a real pitty that the robbe box does not seem to be available in the US...

from scratch only an Arduino + LCD&keyboard shield comes to my mind, but I think this wouldn't be cheap, on the order of 30-40 bucks I guess... I could send you a new robbe box... but this would take another few weeks... or if the the lcd can be identified as the broken item you could look for a US based vendor of it... it is a "compatible" 2x16 lcd, and should not be too difficult to find...

Last edited by OlliW; Aug 25, 2011 at 07:44 PM.
Aug 25, 2011, 05:03 PM
BTW, in your photos I see an incorrect installation... the yellow-marked GA250-GM servo cable should not be plugged in tt the reciever...

I guess I should grab this occassion and should tell what the five servo cables coming out of the GA250-gyromixer are

the red and black servo plugs of the four-wired cable marked with a BLACK heat shrink tube are
red servo plug: throttle
black servo plug: rudder

servo cable with RED heat shrink tube: connector to the ESC for motor A (upper rotor)
servo cable with BLUE heat shrink tube: connector to the ESC for motor B (lower rotor)

servo cable with YELLOW heat shrink tube: I will call it the PROGRAMING CABLE
this has a dual functionality
1) connector for programming the GA250 via the prog box
2) connector for flashing of a new firmware

hence, the yellow programming cable should just be left unconnected... you would connect your prog box to it when you want to program the GA250-GM
Last edited by OlliW; Nov 04, 2011 at 06:44 PM.
Aug 26, 2011, 05:09 AM
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Haha, beautiful! My coax installs are all mock ups at this point. I have to properly check vibes and padding, proper servo plugs, esc plugs, ect. ect. I just wanted to trial mount the units and see what I am up against. It is 2am here and I am programming an Sk720 so I will definitely get these going this weekend or early this week.

Man, I am soooo glad the smoke trail on the screen side is fairly normal. I just didn't want to destroy all your hard work by doing something stupid right off the bat and ignoring obvious signs of damage. I am pretty excited to get into these!
Aug 26, 2011, 06:39 AM
Man, I am soooo glad the smoke trail on the screen side is fairly normal.
well, we may first want to check that... but considering that the box worked fine in Germany I'am quite optimistic...

I think in the following it would be "clever" to go slowly step by step, and to get first one heli flying. It seems that there a couple of "little" details which are quite obvious once realized but are not necessarily realized immediately (as e.g what t do with the yellow cable ) which one should pay attention too... that's at least what I learned from Tommy@LA's conversion... whenever we followed a clearly defined path, quick progress was made...

From my side, since I would like to have you having a technically "perfect" setup, I'd first would attempt the reflashing of the box and of one of the GA250 GM's... you have to "learn" that anyhow, but it might be not the fastest route to get a first heli flying succesfully... Hence, one also could just try and use the hardware as it currently is.

ideally, you would have a coax heli similar to a ESKy lama v4 or big lama, with the BL motors and ESCs installed, but with no other fancy modding stuff such as flybarless conversions... once you got such a heli flying you will got used to the GM and will have all the experience for the more advanced setups. So, this would be my recommendation, to start with the most "simple" BLBL coax and to work out all issues (or non-issues ) for this one first...

So what are your ideas here, what you'd like to do next/first?
Aug 26, 2011, 02:06 PM
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I agree, I had planned on doing the reflash on the easiest flybarred coax Ga250 system first, and getting everything dialed in on it before proceeding into the much more complex issues involving the flybarless coax's. They are certainly going to demand my full attention.
From my point of view it will be far more forgiving and much easier to learn with.

I had thought about doing a full 5 gyro Production style reflash, one after the other so I could get them all buttoned up. Then I could take on individual programming later on each one since each heli is so vastly different.
Aug 26, 2011, 02:56 PM

Maybe we first try to do the most difficult thing, namely to reprogram the robbe box to get the appropriate bootloader onto th uC...

It is most difficult, since you have to do some soldering work. You also will need some sofware.

BTW, Tommy@LA had to do the same thing, so, in his thread you may also find some information... if you are willing to use google translator... the relevant part would start here

Anyhow, what you need and have to do is this:
Aug 26, 2011, 03:00 PM
Programming the Bootloader into the Robbe Box: I. Hardware

A good picture of the inside is here

relevant for you are the ISP pads, these are the six pads which are labeled in red as GND, MOSI, MISO, SCK, RESET, VCC in the small bottom right photo, and which are connected to six cables in the big left photo (the other stuff related tio the red circle is irrelevant for you!).

Ensure that you understand which of the pads do relate to GND, MOSI, MISO, SCK, RESET, VCC.

Now, solder cables to ONLY the FIVE Pads GND, MOSI, MISO, SCK, and RESET. You don't need to solder a cable to VCC (BTW, the cable thickness and type is completely irrelevant).

Now, take the USB-TTL-Adapter, and disconnect the pin-plug (i.e. take away all teh stuff with the cables, switch, etc...). In the following you only will need the red board with the USB connector on one side and the 6-pin connector on the other side.

Each pin of the 6-pin connector should be labelled with the symbolsGND, CTS, VCC, TX0, RXI, DTR.

You now need a 6-pin connector strip, or any other means to connect cables to the pins of 6-pin connector of the USB-TTL-board. The following FIVE pins on the USB-TTL-board have to be connected to the following FIVE ISP-pads on the robbe box:

red USB-TTL Board -> Robbe Box Pads
RX0 -> SCK

triple check your connections! The VCC pin on the USB-TTL-board is not connected.

You may have realized that the VCC ISP-pad on teh robbe box was not used. The power for the robbe box you will in fact provide through the servo connector of the robbe box, i.e., you may connect the servo cable of one of your ESCs to it, and power the whole thing by then connecting the ESC to a lipo.

That's the hardware part to be done.

Programming the Bootloader into the Robbe Box: II. Software

Next you need some software. namely a modified version of avrdude, as well as the window drivers for the USB-TTL- adapter. The latter you may get from the FTDI web page, you'll need the VCP dirver for your windows version
-> VCP (Virtual COM port) driver

The modified avrdude I have attached as zip. Unpack it into a folder of your wish, but ensure that everything is in one folder.

I will continue with part III. once you have done all that
Aug 27, 2011, 03:20 AM
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Thanks! I was going to question you earlier about the red circled area where they removed a component so you beat me to it. As I said this is all getting addressed in the next few days. So cool. I am actually looking forward to the soldering part. Fairly easy considering I have been removing and re installing full micro chips this last year. Not all successfully I might add. Yep, I can still mess something up. This project rocks OlliW! Thanks for inviting me in to the process!
Sep 09, 2011, 11:52 PM
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Finally, the rush of people pouring through my life has slowed down and my Sk720 builds are done for the moment. So now I am going to solder the leads and get this project moving again. Thanks Olli, in-between the pm and this post I have a pretty good idea of what goes where. I am going to have all this up and going by monday at the latest after this weekend. I am sure I will have a few questions.

Here is what I accomplished inbetween multiple phone calls (people calling me) tonight. I cut off the 7 pin connector off an extinct 6100e Rx and used it as my pin connector. This way I could move the set pins where I needed them. The soldering only took about 5 minutes. Most of that was warming up the Iron. I soldered in the 5v pin just because I wanted to anchor the 3 wire lead, but it is turned back at the board. And I have an Ice50 esc to use as the esc power in. And CDM20817 is installed off the site and ready on my vista in my download file along with the custom file you posted. Are these supposed to be in the same exact file together? Not sure how to do that if needed.
Last edited by Luvmyhelis; Sep 10, 2011 at 02:47 AM.
Sep 10, 2011, 03:29 AM
as much as I can tell this looks good...

Are these supposed to be in the same exact file together?
Not sure how to do that if needed.
I'll double-click the zip, and then grap the files in there and drag them to the folder I like... I rarely use the extract button

unfortunately I am extremly busy... have to do a lot of bussiness work... and can't hence communicate much... sorry for that...

but hopefully you'll get along

I have not yet described the third step of actually flashing the bootloader, but in the zip file you'll find a readme you may find helpful, just pay attention that you have a ATmega88PA... also in Tommy's thread on rcline you'll find very detailed step-by-step instructions + pictures of how things should behave (its in Gemran but google translator isn't bad).

there is only one "trick" I've encountered... somehow the avrdude communication with the red board is not always reliable (so it was at least on my computer), if you hence encounter a problem (avrdude will tell you), disconnect and reconnect the usb cable from the PC and try again (but please wait long enough for windows to establish connection)... it's a bit nasty...

good luck

I'll peek into here whenever I can


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