FrSky DJT PPM input format and pinout

[yogi]

Hi,

This is not strictly a 9x question, however it's related and I'm hoping I can get some help. I've trawled through the forums and Google search and haven't been able to find an answer to my questions.

For my project I wish to feed the FrSky DJT TX module with an Arduino generated PPM signal. The questions that I have are:

- Based on info I've gathered, the pinout of the DJT module seems to be as follows:
(starting from top [i.e. antenna side])
- PPM
- NC
- VCC
- GND
- NC
Is the above correct?

- Is the input PPM signal to the TX module of a 'standard' non-inverted format (gap between rising edges define the PWM pulse width for each channel - as described here http://sourceforge.net/p/arduinorcli.../PPM%20Signal/ )?

- The Arduino (nano) outputs a 5V pulse height. Is this within the acceptable range for the DJT module?

Apologies if these have been answered before. Any insights will be appreciated.

Thanks,
Yogi

[Kilrah]

Pinout is correct, 5V is fine and polarity doesn't matter, it will happily take both

[yogi]

That's great. Thank you so much for getting back to me.

[Starscream]

@yogi

Hi yogi,

have you resolved your problem?
I've started to work on something which is similar to your project: I want to send some PPM input to an XJT module, so it can transfer them to a remote D8R-II receiver.
Did you get your goal? If so could you give me any suggestion, please?

Thank you in advance...

[MikeB]

Are you using the XJT in isolation, or is it in a transmitter?

Mike.

[Starscream]

It is into a Taranis X9D radio...
I've opened it but I can't undestrand where's the right pin I have to connect to, to send the PPM input.

The XJT built-in module I supose is this, because there's soldered antenna's wire on it:

[MikeB]

Suggestion:
Use the trainer input and send your PPM signal in to this.
Now set your mixers to:
CH01 +100% PPM1
CH02 +100% PPM2
CH03 +100% PPM3
CH04 +100% PPM4
CH05 +100% PPM5
CH06 +100% PPM6
CH07 +100% PPM7
CH08 +100% PPM8

The the internal module to PPM.

Your PPM inputs will now be sent to the XJT module.

Mike.

[Kilrah]

I've opened it but I can't undestrand where's the right pin I have to connect to, to send the PPM input.

But you also want to send the radio control orders, right? If yes you cannot connect directly to the module. It only has one input, and that's where the radio sends info to. You can't send something else there at the same time. You have to go through the radio's trainer port as Mike explained.

[Starscream]

Thank you very much for your help!

I've configured my radio in this way:

- Mixers setup:

Mixers

- Trainer setup:

Trainer

I've tried to send some PPM signals with Arduino from the trainer port, the D8R-II receiver got them and so I can move my servo (jut for test). It works but not completely. Actually the sevo moves but not as I wish.

So I build my PPM signal (e.g. for channel 1) and then I send it.

Could I ask you any help about the code to generate the PPM signal, or this isn't the right place?

Thank you again for your answer!

[MikeB]

A good place to discuss something like the code for the Arduino is to create a thread here: viewforum.php?f=84.

Could you be a bit more specific about what is wrong with your servo movement?
BTW, since you are using the PPM mix sources directly, you don't need the TRAINER screen. However, the CAL numbers at the bottom of the TRAINER screen show what the transmitter is receiving from the trainer port. If the pulses are going from 1.0 mS to 2.0 mS you should see these CAL values gor from -100 to +100.

Mike.

[yogi]

Hi Starscream,

I didn't use the trainer port for my project. I used the Arduino to send the PPM directly to a TX module.

If you're looking of the PPM generator code, there's a good description of the mechanics and the code in this blog....http://www.ianjohnston.com/index.php?op ... s&Itemid=8

Let me know if that helps.

[Starscream]

Thank you yogi!

I'm near to the goal... I'm able to generate the PPM signals from my Arduino, which is controlled from the PC.
These signals are sent to the radio's trainer port and everything is received correctly on the other side (receiver D8R-II).

I've told "near" because I have a little problem on CH5 which corresponds to the fligh mode channel. When I go to "CHANNEL MONITOR" page on my Taranis there's a "-100" value on CH5, even if I do/don't send PPM signals to the radio's trainer port. The same thing happens when I go to "SERVOS" page, there's an arrow which points to "-100", an there's not a dash like on other channels.

You can see it below:
- "CHANNEL MONITOS" page
[thumbnail]download/file.php?mode=view&id=7850&sid ... 57171c7f6f[/thumbnail]

- "SERVOS" page
[thumbnail]download/file.php?mode=view&id=7851&sid ... 57171c7f6f[/thumbnail]

Could you give me (again) any suggestion on how could I resolve this problem, please?

Thank you in advance...

[Kilrah]

Which firmware on the radio? There was one particular version where PPM5 wasn't working. You should use the latest (2940).

[Starscream]

I think it's version 2751, if I'm not wrong.

On "VERSION" page of the radio there's written:

SVN : opentx-r2751
DATE: 2013 - 09 - 01
TIME: 24:40:55

EEPR: 215

[Starscream]

Sorry if I ask you Kilrah, but I saw your name on GitHub under the firmware release (r2923).
Could you tell me how and where can I get the last firmware.bin?
I've used the link on GitHub but is just for the source, and I've tried to get it from Companion9x but it says that there aren't available updates.

Thank you...

[yogi]

Hi Starscrean, Sorry, I'm not familiar with the Taranis. However, I can suggest a few things you can check to make sure the Arduino PPM signals are correct:

- If you have an oscilloscope, are you able to check that the PPM signals generated by the Arduino have the correct form? If not, you can try building an Arduino based oscilloscope (http://code.google.com/p/xoscillo/)

- You can also try feeding the Arduino PPM signals directly to the DJT module. You can then check the behaviour of channel 5 by connecting a servo to the receiver.

Good luck. Let us know how you get on.

[Kilrah]

Just use the Download button next to the firmware type in companion9x's preferences. If it says no updates you already downloaded the latest at some point but likely forgot to flash it.


Envoyé de mon iPad à l'aide de Tapatalk

[Starscream]

Hello you again, I've finally resolved everything.
As Kilrah said I updated my taranis firmware and now the PPM5 works very well, so THANK YOU KILRAH!
And talnking about the PPM signal generated from my Arduino, I've used the "scope" yogi suggested and I've found it very usefull, so THANK YOU YOGi, too!!
You have been very patient and kind with me, thank you!

In the end I'd like to ask you a last question about Taranis programming (I don't know if this is the right place where I can ask it).
I'd like to use the two position SF switch on the radio, to change the PPM source of the channels.
As I said before I wanted to send the PPM signal from my Arduino to the the trainer port of the radio and to get this signals on the receiver side, and I got it.
Now I want to keep this "version", and also to be able to send the signals with the Taranis, by moving its sticks!

Is this thing possible? How could I change the sources?

Thank you again, in advance for you help!

[MikeB]

Do you have, for example, channel 1 set up as?:
CH01: +100% PPM1
If so, add a second mix to this:
CH01: R +100% Ail switch(SF)
THis uses a Replace multiplex, so if switch SF is ON then channel 1 will send out the transmitter Aileron stick position, if SF is OFF, then the output will be from the PPM1 input.

Mike.

[Starscream]

Thank you very much @MikeB!

[Starscream]

Hello you again!

After my Taranis update, I've tried to arm and "play" a bit with my hexa.
I've seen that the radio isn't as responsive as before.
What I mean si that when I move the throttle stick up and down, it takes a little time to the multirotor to recognize that the valuse has changed, so it seems to be delayed.
I've reloaded the old firmware on the Taranis and tried the same things and it works, but the PP5 doesn't work (thats why I updated the firmware).
So in the end I've uploaded the new firmware again...

Could you tell me please how can I resolve this problem?
As you can see, I can't fly with the multirotor because it's dangerous..

Thank you for you help!

[Kilrah]

Can you explain how you see that and post your settings? Nothing has changed there.

[Starscream]

Forgive me if I answer you so late...

I've checked the setting and it seems that nothing has changed, so I can't understand where I'm wrong.
The only thing I've changed is the "DEFAULT CHANNEL ORDER", into radio setup, from RETA to AETR...

I can see that behaviour by "looking" at the motors' speed. When I increase the throttle value by moving its stick up, they don't spin faster but they have the same speed. The motors change their speed only when I'm nearby the maximum value of the throttle stick...

And if I want to update their speed I have to move up the stick (so the motors can see the value changed), and then move it down to the desired position.

[Helle]

Hy,

did you Sticks and Potis new kalibrate after Firmware updated ??

what do you see at the Channel monitor
are the bars fast?

Helle

[Starscream]

Forgive me if I'm so late.
The proble was with the calibration of the sticks.

Thank you again people!!!