PPM Frame size

Hardware Support for the 9XR
Post Reply
afon
Posts: 25
Joined: Mon Aug 24, 2015 8:59 am
Country: Germany
Location: Hamburg

PPM Frame size

Post by afon » Thu Aug 27, 2015 5:40 pm

Hi All,

I have Turnigy 9XR + FrSky DJT + FrSky D4R-II

D4R-II was flashed with 27ms firmware because I want to use 7 channels.

My question is: what PPM frames size should be set in TX settings (openTx or er9x)?

At this moment in my TX settings I have (by default) PPM Frame 22.5ms 300u Negative

Is it OK?

I am not sure, that it is OK because D4R-II waiting for frames with 27ms size.
Last edited by afon on Thu Aug 27, 2015 8:24 pm, edited 1 time in total.


User avatar
MikeB
9x Developer
Posts: 16901
Joined: Tue Dec 27, 2011 1:24 pm
Country: -
Location: Poole, Dorset, UK

Re: PPM Frame size

Post by MikeB » Thu Aug 27, 2015 7:16 pm

How many channels are you sending, 8 I would guess since you want 7, and you have to choose either 6 or 8.
I would suggest allowing 2.1mS per channel and at least 4.5mS for the sync time so, for 8 channels, that is 8*2.1 + 4.5 = 16.8 + 4.5 = 21.3.
21.5 is the minimum to use so the default of 22.5 is fine.
The D4R generates the output CPPM using 27 mS, but this is independant of the rate sent from the Tx to the DJT.
So, 22.5mS is perfectly OK.

Mike.
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

afon
Posts: 25
Joined: Mon Aug 24, 2015 8:59 am
Country: Germany
Location: Hamburg

Re: PPM Frame size

Post by afon » Thu Aug 27, 2015 8:26 pm

Hi Mike.

Thank you very much. Your answer really helped me to understand underlying settings.

I will leave PPM Frame size "as is" (22.5ms)

User avatar
Buzzliteyear
Posts: 30
Joined: Wed Sep 11, 2013 10:20 pm
Country: New Zealand

Re: PPM Frame size

Post by Buzzliteyear » Wed Mar 04, 2020 7:10 am

Hi Mike ,
can i use the same formula for 12 channels Sbus LRS and ER9x on turnigy 9x 12 x 2.1 + 4.5 = 29.7 + 4.5 = 34.2ms ?

no option above 32.5ms in my FW version

Brett

User avatar
Kilrah
Posts: 10551
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: PPM Frame size

Post by Kilrah » Wed Mar 04, 2020 7:42 am

What module?


User avatar
Buzzliteyear
Posts: 30
Joined: Wed Sep 11, 2013 10:20 pm
Country: New Zealand

Re: PPM Frame size

Post by Buzzliteyear » Wed Mar 04, 2020 9:29 am

Ebyte Lora module 433,
I just manager to hook it up and try and it wont work on selecting Sbus
is there Sbus output from turnigy 9x with er9x firmware?

Brett

User avatar
Kilrah
Posts: 10551
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: PPM Frame size

Post by Kilrah » Wed Mar 04, 2020 9:34 am

If you output SBUS then PPM timings have nothing to do with it...

User avatar
Buzzliteyear
Posts: 30
Joined: Wed Sep 11, 2013 10:20 pm
Country: New Zealand

Re: PPM Frame size

Post by Buzzliteyear » Wed Mar 04, 2020 10:04 am

Ofcoarse .....i see now.....

i dont understand the sbus output, If i move the throttle it is like the gap in the first pulse increases
Attachments
Clipboard09.jpg
Last edited by Buzzliteyear on Wed Mar 04, 2020 12:16 pm, edited 1 time in total.

User avatar
MikeB
9x Developer
Posts: 16901
Joined: Tue Dec 27, 2011 1:24 pm
Country: -
Location: Poole, Dorset, UK

Re: PPM Frame size

Post by MikeB » Wed Mar 04, 2020 10:42 am

er9x does support SBUS, however this is "standard SBUS" currently that is inverted, logic 1 = 0V, logic 0 = positive voltage.
SBUS is sent at 100000 baud. Your logic capture is sampling at 20kHz (20000) so is not fast enough. To capture 100000 baud, you need to sample at least twice as fast as 100kHz, I would use a sample rate of 1mHz.
Does your module accept the inverted signal?

I make the PPM calculation:
12 x 2.1 + 4.5 = 25.2 + 4.5 = 29.7ms ?

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

User avatar
Buzzliteyear
Posts: 30
Joined: Wed Sep 11, 2013 10:20 pm
Country: New Zealand

Re: PPM Frame size

Post by Buzzliteyear » Wed Mar 04, 2020 12:37 pm

No it does not accept inverted signal I made this inverter with BC547,
I did another sample @ 1mhz after the inverter and got about 66 frames (only about 15 shown in pic below)... does that seem normal ?
Attachments
invertor.jpg
Clipboard01.jpg

User avatar
MikeB
9x Developer
Posts: 16901
Joined: Tue Dec 27, 2011 1:24 pm
Country: -
Location: Poole, Dorset, UK

Re: PPM Frame size

Post by MikeB » Wed Mar 04, 2020 7:09 pm

Your SBUS signal is not correct. You should see about 9 frames per second (1 every 11 mS), and the waveform should be a standard UART at 100000 baud, 12 bits per character, 1 start, 8 data, 1 even parity and 2 stop.
Try checking the signal from the radio, on the 9X, this is at 5V.
You might also check your connections to the BC547.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

User avatar
MikeB
9x Developer
Posts: 16901
Joined: Tue Dec 27, 2011 1:24 pm
Country: -
Location: Poole, Dorset, UK

Re: PPM Frame size

Post by MikeB » Wed Mar 04, 2020 10:24 pm

I've just posted a test version of er9x that includes a polarity option for the SBUS protocol output.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

User avatar
Buzzliteyear
Posts: 30
Joined: Wed Sep 11, 2013 10:20 pm
Country: New Zealand

Re: PPM Frame size

Post by Buzzliteyear » Thu Mar 05, 2020 6:09 am

Ok it is working

not sure why but this is the hookup

9x signal is inverted going through inverter = non inverted signal to Tx Lora module

Rx side = Rx Lora module feeds inverted uart 6 PPM/Sbus pin only ( not uart 1,3 or 6 on the left side on the omnibus F4 v3)

thanks heaps for the help Mike

User avatar
Buzzliteyear
Posts: 30
Joined: Wed Sep 11, 2013 10:20 pm
Country: New Zealand

Re: PPM Frame size

Post by Buzzliteyear » Thu Mar 05, 2020 7:16 am

822c ? I just flashed that cant see polarity option............

https://openrcforums.com/forum/viewtopi ... 598#p64969

Perfect Works Great thanks again........dont need that invertor now.......where the donate button :)

User avatar
MikeB
9x Developer
Posts: 16901
Joined: Tue Dec 27, 2011 1:24 pm
Country: -
Location: Poole, Dorset, UK

Re: PPM Frame size

Post by MikeB » Thu Mar 05, 2020 10:10 am

There is one on here: https://github.com/MikeBland/mbtx, or "jhsa" has a link at the bottom of his posts.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

User avatar
Buzzliteyear
Posts: 30
Joined: Wed Sep 11, 2013 10:20 pm
Country: New Zealand

Re: PPM Frame size

Post by Buzzliteyear » Fri Mar 06, 2020 2:43 am

Done cheers.......Brett


Post Reply

Return to “Turnigy 9XR radio”