Spektrum Module mod - Aurora 9 related - Page 3 - RC Groups
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Apr 28, 2010, 03:12 PM
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Jul 17, 2010, 04:32 PM
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Hi Guys
I had an idea as i woke up this morning...
Follow my thinking, let me know where i might be wrong:
-Optic 6 and Eclipse transmitters have a similar pin layout to Futaba modules, which is the same as conventional old Hitec modules
-Aurora transmitters have a new pin layout
-2.4GHz Hitec modules can work with both pin layouts

To me that means that 2.4GHz hitec modules have a "conversion" bit of kit between either the old or new pin layout and the proper 2.4GHz part of the module.

So now, what if some clever bloke could find out how the signal coming out of either old or new pin layout is converted to be used by the new 2.4GHz module ? Then that conversion would have to be implemented into DSM2 modules for Futaba...

Does that make sense to you?

I wrote to spektrum as few month ago: they have no plan to manufacture modules for Aurora in a near futur... bol*cks! but i can get to the idea of not flying my dsm2 kits with my baby aurora!!!

Thanks for reading... and thanks a lot for your replies!
Jul 17, 2010, 06:13 PM
Inciting Riots
village_idiot's Avatar
Lots of not searching for the correct operation of the Futaba type modules.

The PPM pin on these modules is pulled up to a voltage (R2), the reason is that the controller in the Futaba radios grounds this pin to make a pulse (open collector output). In order to interface these modules to other things, sometimes that pull up needs to be removed because the TX actually has an active signal on the line (like the Multiplex radios). You need to know if there is a signal on the PPM from the radio or if it is doing something else, even one of the free audio card o'scopes should be able to tell you if there is a PPM signal or not. You could also connect a small audio speaker (headphones) between PPM and ground on the A9, if you hear a rapid clicking or a tone, then there is an active PPM signal to use. Since it isn't working, I'm assuming there is a signal (can only assume since I don't possess an A9). If you don't want to remove the resistor, you can make a transistor buffer out of an NPN transistor, pulling the resistor is much easier.

Next the voltage regulator that seems to run everything inside the Spektrum modules is a 3.3 volt LDO regulator, so anything above about 4.5 volts should make it operate just fine, I've used one at 7.1 volts with no problems, other people have been using it with 2S A123 power and 5s Nimh, 4S Nimh might be pushing things but should still be fine. The spec. sheet says it will tolerate up to 16 volts, but I wouldn't try it past 8S Nimh or 3S lipo.

Proper placement of the ground wire for these Futaba sized modules is on pin 4, you should move the wire over so that people do not get confused. Not all Futaba sized modules short pin 3 and pin 4. Pin 3 really does something, but no one took advantage of it which was extremely short sited (in my opinion). Pin 5 does nothing with these 2.4Ghz modules, with the FM/PCM modules it connected to the long antenna.

Another thing you need to check is the timing on the PPM pulse train. It has been determined that you really can not exceed 25ms between sync pulses or the module goes nuts, 22ms for the DM9. So you really need to check the length of that pulse train to see if it even still fits, they could be correcting this in the A9 module, or maybe not. Futaba ran 8 channels FM, 9 in PCM but number 9 was on or off so not a lot of space used.

Now looking at this post, it seems that the pinout of the A9 has been completely scrambled compared to previous designs:

Again I can not verify any of this since I do not have an A9. If someone would like to send me one (to keep), I will come up with a plan to rig a DM8 to the A9 TX.
Jul 17, 2010, 08:11 PM
High-power Rocket Gliders
iter's Avatar
Originally Posted by village_idiot
Not all Futaba sized modules short pin 3 and pin 4. Pin 3 really does something, but no one took advantage of it which was extremely short sited (in my opinion).
Pin 3 reports transmission strength back to the radio. I am with VI--not using this pin is a waste. Since it's function in life is already to communicate information from the module to the radio, one use for it is to communicate module capabilities to the radio, as well as telemetry. Backwards-compatible operation can use ignore or ground that pin, but if both TX and module agree, they can use it e.g. as serial RX line.

It seems that companies are moving away from module radios in general. Putting the RF section in a module commoditiezes it. Vendors must put a price on it, and it can't be high on account of (Chinese) competition. When you come to buy a $1,000 radio, you know that the RF section costs $50. So the manufacturer has a harder time justifying that $1,000 price. If they integrate the module (and its price) into the radio, they can imply that a big part of what you are paying for is the extra-special, secret RF voodoo.

Jul 19, 2010, 05:08 AM
Registered User
Hi all
Thanks a lot for your replies. Village idiot is not that idiot then !!!
Your knowledge is far higher than what my likkle brain can cope with... shame you dont have an A9 to play with...
I'll have a go with your explainations and all other bits and pieces i found on rc group...
I keep you updated!
Jul 26, 2010, 10:02 AM
Registered User
I have been trying to do exactly the opposite, putting a Spectra Module on a JR radio, so far have found the following: When hacking the module to a JR 8 channel radio(XP8103) everything works perfectly(even when both radios have diferent PPM shifts), but when I tried it with a JR 9 channel radio (xp9303) the module would not work and actrually go nuts, seems the issue is related to the A9 PPM signal including the 9th channel, reverse engineering it, I would expect that the A9 outputs a 9 channel PPM signal that the Spektrum module can't read.
Aug 08, 2010, 05:22 PM
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Mmmm... does it mean "end of story" ?
Aug 13, 2010, 02:37 PM
Registered User
how about using a 9 channel module for JR on Aurora transmitter ?
Aug 13, 2010, 05:59 PM
Inciting Riots
village_idiot's Avatar
Timing for the JR type modules is 22ms or so, the Futaba is 25ms so you need to know how long the pulse train is. If you give the JR type a 25ms pulse train it will freak out.
Aug 25, 2010, 07:23 AM
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I have to say that i dont have the knowledge to go any further. Any of you motivated well enough to carry on ?

I had a chat with some guy at HorizonHobbies. He told me that Spektrum would not develop any other module for any other brand as they now have a whole range of transmitters...

Please guys switch your brains on ! I will receive my ultra micro 4sight this week...
Aug 28, 2010, 10:33 AM
Registered User
Last option : why not connect that DSM2-futaba module to the buddy port of the Aurora ?

I have seen a similar mod for EVO9... i guess it's not just putting voltage into the DM8 and signal from buddy cord... ?
Sep 30, 2010, 11:49 AM
Registered User
Hi guys

Here is an update !

I have set up an osciloscope with a sound card, coupled to a tension-divider and got some readings.

I also made a conversion cable to get a DM8 module to work on any Multiplex buddy port... it works.

I also took measurements from my Eclipse transmitter fitted with that DM8 module...

In the end, i tried to connect the DM8 straight to the Aurora, and then strainght to the buddy port of the Aurora (with a tension divider, as the signal out of buddy port is far too high). Doesnt work either way.

I tried my best to match V+ and PPM voltage as close as possible to those measured on MPX and Eclipse transmitters...

The only difference is that the Aurora outputs 10 spikes every 25ms against 8 spikes for MPX and Hitec transmitters.... could that be the source of our troubles ?

What else could that be ? Neg and pos shifts dont seem to bother that DM8 module as both MPX and Eclipse give different shift, it works either way...

Would it be possible to "cut" the final 2 spikes ? Is there another Spektrum module that would match those specs better ? Is it really those 10 spikes that confuses the mod ?

Thanks for reading, thanks even more for your help !
Sep 30, 2010, 11:53 AM
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village_idiot's Avatar
The module will not accept 10 pulses per frame, if you can't find a setting in the software to limit it to 8 pulses then it probably wont work.
Sep 30, 2010, 04:15 PM
Registered User
Any other module that would take up to 10 pulses ? plus 25ms pulse train ? and DSM2 on top of that !!!

how about those funny shapped modules for futaba MZ radios ?
Sep 30, 2010, 05:45 PM
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village_idiot's Avatar
It would be a lot of work, but the Spektrum module for the Multiplex EVO might work, I would suggest a lot of research before dropping the huge load of cash on that device since they will not sell it without the 12 channel receiver and you will take a bath on selling the receiver.

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