Frsky PPM sum hookup

[signal15]

Anyone know how to physically connect an Frsky receiver to get PPM to the MW board?

Some of the stuff I read over mentioned 3.3v and the risk of frying something.

[signal15]

Anyone?

[UndCon]

HI!

I use PPM on Frsky

enable PPM that suits your radio in config H

I have this:
#define SERIAL_SUM_PPM ROLL,PITCH,THROTTLE,YAW,AUX1,AUX2,AUX3,AUX4

then you enable PPM on your Frsky receiver according to the manual
like holding button when powering up?

Then you connect a single servo wire between the board you use and your receiver.

I use Paris boards and the PPM signal is on throttle inputs. On the D4FR it is the ch2 that is PPM out
A jumper between ch3 and ch4 is also used.


Note - there are some issues with PPM on Frsky that creates glitches


http://www.youtube.com/watch?v=UQDv7i3D ... e=youtu.be

viewtopic.php?f=8&t=1584

[signal15]

What kind of glitches?

[UndCon]

I think I solved my glitches - most likely the wrong ms value in PPM.
(should be 18ms instead of 22.5 as I used)

[Lapino]

Are you able to use all 8 channels with cppm? i have glitches when using let's say 6-7 channels with full deflection and move one remaining channel... That's caused by that said 18ms which are too short to fit this channel count with all channel fully deflected...

[trex450]

From FrSky


CPPM channel can not handle all eight channels at the same time with all throws are maxed out, as it does not have enough frame gap. It is recommended to use at most six channels from CPPM channel while leaving off the rest two channels, otherwise improper performance might occur.


http://www.frsky-rc.com/ShowProducts.asp?id=126

[signal15]

Well crap. I upgraded my 9x to Frsky just to get PPM.

[Lapino]

Me 2...I've read about this a few weeks later
Good to know though

[wilco1967]

Don't worry too much about this......
The problem is there (theoretically), but in real life, you won't notice.

I'm flying FrSky with 8 (yes, eight) channels PPM for almost a year, and never had any problem in flight.
Only on the bench, I can replicate the problem, but you have to put the sticks all in the corner, and the switches at high to see it. That won't ever happen in real flight.

The problem shows up when the average pulse length of the 8 channels exceed the total availalble time slot (of approx 22 ms...), and the start pulse gets too narrow.

I would recommend to configure your aux1 to aux4 switches not from 1500 to 2000 (mid to high), but from 1000 to 1500 (low to mid). I only have one 3pos switch (9X), which is 1000,1500,2000 us.
Never encountered any problem. (not even before , when I used 1500 -> 2000 switch configuration).

[pfluggeraet]

Hi...
I pick up this thread, as things might have changed.
I bought a new frsky V8R7SP receiver, and in the manual states that it now uses a frame-time of 20ms. With my Graupner MC15 i tested how small the gap between 2 frames may become, after adjusting all sticks to 125% travel. I still get more than 4ms of gap between the last pulse of the old and the first pulse of the new frame. So far this looks perfect to me...

Having checked the latest version of Multiwii-shared 2.1 i found out, that it waits for a pule of 3000us to start a new frame. This should work fine.

First i thought something is wrong. When giving full throttle and full pitch, combined with switches in the "long pulse position" the cycle-time of the Multiwii-Software jumps from 3000 to 23000 or even -19000 (looks like overruns) and the GUI starts to hang for seconds. The channel values still look ok. When centering the sticks, all returns to normal. On my oscilloscope everything looks good. Enough gap to detect the frames, nice pulses.

Then i found out this happens only in non-Armed mode, and the reason for this is, that certein stick-combinations cause the eeprom to be read or written, and that is not real-time-conformant, so the cycle time goes up...

So it looks like this ppm-sum feature may now safely be used, at least with the V8R7SP.

[thornton]

I have a similar problem under DEV1155.
Using a Frsky D4R-II with PPM-SUM output i get cycle times about 25000-26000,
if i give full throttle AND full pitch. This exactly happens in the moment when the sum of pitch and throttle reaches 3900.
After a short moment cycle time goes down to normal values.
It does NOT depend on whether pitch is 1900 and throttle 2000 or reverse. It is just the sum of both reaching 3900.
It also does NOT depend on other channels. I tried to "maximice" the output of all channels, but it only happens with pitch and throttle.
So it doesnt seem to me to be a problem of Frsky PPM-SUM.
Hope this can help.

By the way: It was my first try to horizon mode, I like it very much. Good work!

[gsantos_pt]

Hello! How can I connect in ppm with a frsky D4R-II to this FC?

I also enabled this line: #define SERIAL_SUM_PPM ROLL,PITCH,THROTTLE,YAW,AUX1,AUX2,AUX3,AUX4

What is missing?

[QuadBow]

Don't worry too much about this......
The problem is there (theoretically), but in real life, you won't notice.

I don't agree, there is an issue - at least with the default firmware.
But there is a solution by increasing the periode time from 18ms to 27ms: http://www.frsky-rc.com/download/view.php?sort=&down=10&file=Firmware-D8R-XP_27ms

I'm flying FrSky with 8 (yes, eight) channels PPM for almost a year, and never had any problem in flight.

With this firmware I agree, there is absolutely no issue any longer...

[Cereal_Killer]

Hello! How can I connect in ppm with a frsky D4R-II to this FC?

I also enabled this line: #define SERIAL_SUM_PPM ROLL,PITCH,THROTTLE,YAW,AUX1,AUX2,AUX3,AUX4

What is missing?

What MCU is on the FC you're using? What pin are you hooked into?