FrSky DJT Module & On Screen Telemetry ?

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BieneFlyer
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FrSky DJT Module & On Screen Telemetry ?

Post by BieneFlyer » Fri Jul 19, 2013 8:03 am

Hey all,

I realise there is a load of info out there regarding this but I want the best solution.

I just ordered a FrSky 2.4Ghz DJT Module & 8 Channel Rx (telemetry).

How, in a nutshell, can I get the telemetry data to the Turnigy 9x screen ?

I see you can buy a seperate display, but to have that info on screen would be very cool. 8-)

Any good youtube clips or info on doing this that are easy to follow ?

Any thoughts, help etc appreciated.

Cheers. BF:)


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Re: FrSky DJT Module & On Screen Telemetry ?

Post by BieneFlyer » Fri Jul 19, 2013 9:07 am

Ah!

It's ok. I just remembered that Smartieparts has that telemetry board.

DUH!

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Kilrah
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Re: FrSky DJT Module & On Screen Telemetry ?

Post by Kilrah » Fri Jul 19, 2013 9:27 am


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Re: FrSky DJT Module & On Screen Telemetry ?

Post by BieneFlyer » Sat Jul 20, 2013 6:37 am

Thanks Kilrah,

I'll look into that too.

Do you think there will ever be a Fr Sky module that will display to either the 9x screen or one of their add on display devices that wont need a cable ?

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by Kilrah » Sun Jul 21, 2013 5:52 pm

I doubt so, bpart from the Taranis of course as it's internal 8-)

But the problem is mainly about the 9x requiring hardware modifications to display anything, and to having something wireless (and need for a battery etc) to replace a 10cm cable makes little sense.


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Re: FrSky DJT Module & On Screen Telemetry ?

Post by ShowMaster » Sun Jul 21, 2013 9:17 pm

I just did a Frsky DJT telemetry mod to a 9x that has the older SP 2.1 board with the EL BL panel. The owner didn't want to upgrade to a led BL.
My switch reroute mod is to cut the traces at the pads on pins 2&3 just as they go to the 200 ohm SMD resistors so I can reuse them to connect to pins 41 & 42. I use a modified max233 board $3 eBay for the rs232 to TTL conversion.
I tap into the SP boards pogo pin pads for MOSI and MISO connections.
I didn't modify the DJT to feed the TXD and RXD data out the unused pins for this owner but instead I feed it with the data connector on the DJT trough a small hole in the case back.
The owner wants to use the module in other brand radios.
This is one of 2 configurations I use. The other one is no SP board and the HK BL.
ImageUploadedByTapatalk1374441456.204609.jpg
ImageUploadedByTapatalk1374441256.835281.jpg
ImageUploadedByTapatalk1374441287.571556.jpg
ImageUploadedByTapatalk1374441319.602156.jpg
Added cap on case top to make it look nice.
ImageUploadedByTapatalk1374441346.852613.jpg

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MikeB
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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Sat Jul 27, 2013 8:57 pm

For telemetry, using the DJT module header, it has been recommended to wire the TxD signal directly to pin 5 of the header socket. This works well, but the signal level (+/- 6V) is too large for the Taranis S-PORT.

If you have modified your DJT in this way
DO NOT
use it in the Taranis.

Now, the problem is, you might want to, if you have some first generation V series receivers you wish to use, as they don't work with the built in XJT module.

I have just modified my DJT in the following way:
DJT.png
DJT.png (1.08 KiB) Viewed 10400 times
The 4K7 resistor limits the positive voltage and the diode clamps the negative voltage to -0.2V.
This makes it safe to use in the Taranis, while it still works in the 9X and on the SKY board.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by kaos » Sat Jul 27, 2013 11:03 pm

Those are the exact reasons I used two spring loaded pin for the DJT Txd, Rxd connection, no exposed wire to pull/reconnect while can be used in any Tx that DJT is designed for. the DJT module is virtually untouched and can be used in any Tx that a stock DJT can be used.
put the RS232 level converted as described by Mike in wiki in the tx that you need and I can use the same DJT module in any compatible Tx as it used to whether it is stock, sky9x or Taranis and maintain the original function of DJT.
I use the same module for my SKY9x Tx which does not need, and don't want the conversion, and also use it in my telemetry modded stock 9X which I put a RS232 level converter in.
Here is what I have:
for the SKy9x Tx which does not want a RS232 conversion:
http://openrcforums.com/forum/viewtopic ... ack#p27009
for the stock Tx which needs a RS232 converter:
http://openrcforums.com/forum/viewtopic ... aos#p39894
the final result:
http://openrcforums.com/forum/viewtopic ... =30#p42975

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by ShowMaster » Sun Jul 28, 2013 1:22 am

Will using the modified DJT module this way be able to pass telemetry to the Taranis via the s-buss?

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Sun Jul 28, 2013 10:19 am

Just tried this, plugged in the DJT, and set a model to use the external module, protocol PPM. The model servos work, but there is no telemetry data.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by jhsa » Sun Jul 28, 2013 12:10 pm

so, no way to get telemetry from the external module then :(
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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Sun Jul 28, 2013 2:00 pm

Confirmed that at the moment only the S-PORT protocol for telemetry is implemented, so DJT telemetry doesn't work on the Taranis.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by jhsa » Sun Jul 28, 2013 2:09 pm

And what about if we use the internal module in "D" mode so we can use our "D" receivers.. will at least telemetry work then?
anyway, I think that telemetry should also work with the external DJT..

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by Kilrah » Sun Jul 28, 2013 2:27 pm

Of course it does work with the internal module, because it puts out the new telemetry protocol whatever the receiver type.

It's planned at some point to allow for DJT telemetry (the DJT choice in the protocols is meant for PXX to external slot and telemetry in "old" format), but as PXX for DJT's isn't there yet, and the limitations (DJT needs to be modified in a different way than for the 9x, internal module needs to be OFF any time you plug a modified DJT) there is somewhat little interest in having it, so it's low priority.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by jhsa » Sun Jul 28, 2013 2:32 pm

I guess there is more interest in PXX for the 9x ;) And that wouldn't be low priority, I guess? ;) :mrgreen:
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Re: FrSky DJT Module & On Screen Telemetry ?

Post by Kilrah » Sun Jul 28, 2013 2:38 pm

If we judge by the number of people talking about it, it looks lower (1 vs 2) ;)

PXX for external is already implemented. But as there's no DJT firmware or certainty about whether FrSky will use the exact same protocol as for the XJT we can't test.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by jhsa » Sun Jul 28, 2013 2:41 pm

well, Guess we must wait for frsky.. patiently... not.. :mrgreen:
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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Sun Jul 28, 2013 3:10 pm

Kilrah wrote:(DJT needs to be modified in a different way than for the 9x
My revised mod is compatible with both the 9X and the Taranis S-PORT, hardware tested as working OK.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by Kilrah » Sun Jul 28, 2013 3:27 pm

Good news :)

Sent via mobile

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by ShowMaster » Sun Jul 28, 2013 3:32 pm

On question Mike.
What happens if after this DJT mod or the older mod is plugged into a stock 9x?
Early on I blew up my DJT module because I missed the ground trace on the backside of pin 2 on the 9x. It had the RXD 2.7k in the pin 2 line, direct wire to pin 5 on the TXD.
I never tried a modified DJT in a stock 9x after that. My reason for asking is as others come on board and see the 9x Frsky mod, then maybe a skyboard, then a Taranis, they may plug their one DJT module in them all. Then maybe help out a stock 9x flyer at the field by plugging in their modified DJT. Time has a way of forgetting warnings.
This new mod looks to make the DJT mod more universal and damage proof and I'll try it as soon as I find my Schottky diodes I bought last year.
I am curious about do's and don'ts for a modified for a Frsky telemetry DJT module.
SM

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Sun Jul 28, 2013 4:27 pm

I'm surprised you blew up a DJT with pin 2 still grounded. That is an input to the DJT serial, and should accept +/- 6V, so ground should be no problem. Likewise, a direct short to ground of the Tx pin should not cause dammage, RS232 drivers should withstand a direct short to both ground, and any other RS232 signal.

I think this new mod should be safe, for both the module and the Tx, whether the Tx is a 9X, modified or not, or a Taranis.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by ShowMaster » Sun Jul 28, 2013 4:51 pm

Surprised me too Mike. I still have the module so maybe I should give it another try and see if I really did damage it? It's been over a year ago this all took place.
I'm much smarter about it all now and you've helped me get this way along with others here and RCG.
I can compare it to a working one.
I'll modify one of mine to your circuit and maybe be brave and try it in my various 9x configs first. The Taranis will be last since it's not critical.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by kaos » Mon Jul 29, 2013 5:50 am

Frysky better fix the DJT telemetry issue quick. in their official web site, and alofthobby's Q/A they all say you can use DJT and VII and D rx, never mention the DJT telemetry won't work. As an end user, I would consider that misleading. Of course, if Frysky just want to be another MIC brand, that is OK. But to get into the major league, they need to do better than this. It is not a 60 dollar Tx any more.

Another question is does Taranis support 24 ch by using int module + x8r and a DJT on the back as of now? In Alofhobby's Q/A it says yes, but some where it also says if you want to use the ext module ie DJT, the program will turn the int module off and use the ext module.
I think it would be better there is a place has a precise compilation of what is and is not working as of now. I don't remember I have read this telemetry thing any where till now.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Mon Jul 29, 2013 7:50 am

An unmodified DJT only provides the telemetry data on the external port. As such, I think it is reasonable for FrSky to say the Taranis is compatible with the DJT. The telemetry would be handled by their external display unit.

The internal XJT module works with the VII and D series receivers, and the telemetry is handled by that.

24 channels should work. The model setup menu lets you enable either or both modules, and select which channels are sent to which module.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by jhsa » Mon Jul 29, 2013 8:11 am

that is true Mike. FrSky never built the DJT to provide on screen telemetry on the 9x. It is supposed to work with their display, which it does. So it works as it should with the taranis. it would be nice if we could update them though :)
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Re: FrSky DJT Module & On Screen Telemetry ?

Post by ShowMaster » Sun Aug 11, 2013 5:35 am

I don't have any bat85 Schottky diodes Mike. I do have some 1n5818's. any chance that'll work?
SM

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Sun Aug 11, 2013 8:49 am

They might work, but as they are high current devices (1 Amp) they have quite a high reverse leakage current ([email protected] - [email protected]). This may load the signal, particularly at higher temperatures, and prevent the data getting through. The SKY board has had some problems due to reverse leakage through high current rated Schottky diodes.

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by ShowMaster » Sun Aug 11, 2013 2:44 pm

Rats! I can't find any in stock locally.

There is eBay and a source in Los Angeles. They are about $1 each but should come fast. I can try Digikey. Is there a specific bat85 part number I want?
I may have one SMD left of the low leakage diodes Brent sent me for the reason you mentioned. Now to find it.

I found this on eBay
http://item.mobileweb.ebay.com/viewitem ... 0910478302

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by MikeB » Sun Aug 11, 2013 3:05 pm

I use the BAT85 because I usually have some, and I know they work well for this sort of thing.
Try a search for "low leakage schottky diode" or "small signal schottky diode". I'd look for:
Reverse voltage 30V
Reverse leakage 2uA (anything under 10uA is fine)
Continuous forward current 100mA (or more)

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Re: FrSky DJT Module & On Screen Telemetry ?

Post by ShowMaster » Sun Aug 11, 2013 3:07 pm

If I can trust the eBay device I posted the link to I can have them pretty fast. Probably faster than Digikey.


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