FRSky changing Firmware for CPPM length

Love the 9x? Use FRSky? Post your questions and answers here!
Post Reply
Irish Steve
Posts: 149
Joined: Thu Dec 29, 2011 10:04 pm
Country: -
Location: Ashbourne Co Meath

FRSky changing Firmware for CPPM length

Post by Irish Steve »

This may be old news, but I've not seen it mentioned here, and I'm not sure if it has any implications for any of the firmwares.
FRSky are working with the developers of the Arduino system in DIY Drones, to change the length of the transmit group, as it has been found that more than 6 channels at high pulse lengths are causing issues with the sync pulse being too short to be detectable.

Test firmwares have gone to the developers where the pulse length is being changed from 18ms to 27ms, in order to ensure that if all channels are at high pulse width, there is sufficient frame length for a sync pulse to still be recognisable.

Does this have any implications for the developers and users here?
Irish Steve

If it was easy, shure, would't we all be doin it?

_

User avatar
MikeB
9x Developer
Posts: 17990
Joined: Tue Dec 27, 2011 1:24 pm
Country: -
Location: Poole, Dorset, UK

Re: FRSky changing Firmware for CPPM length

Post by MikeB »

I would assume this change is in the receiver only. As, long as the pulse spacing between pulses on individual channels is still 18mS, then extending the total time for the combined PPM output is something that has been needed for some time. 8 channels, all at 2mS, is 16mS, so there is not enough time for a sync. pulse.

Mike.
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

I have the firmware here for testing, I'll have a detailed look with the logic analyser later today. Indeed, no implication on the firmware, it's only the receiver that will (finally) correctly generate the PPM stream it supplies.
27ms is a somewhat unnecessarily slow refresh rate for 8 channels, but I prefer slow and reliable than fast with a serious risk of loss of control... Most users of the PPM output aren't flying competition 3D machines anyway.
Irish Steve
Posts: 149
Joined: Thu Dec 29, 2011 10:04 pm
Country: -
Location: Ashbourne Co Meath

Re: FRSky changing Firmware for CPPM length

Post by Irish Steve »

Ok, that sounds encouraging, now, living dangerously, would that mean that if the PPM output were to be fed to another processor, which is what's normally happening, a 27 ms refresh rate would allow more channels to be packed into the packets. Clearly the standard 8 channel RX can only deal with the 8, but if I read it right, something like a small Arduino would be able to decode the "extra" channels and output them as either servos or digital channels. Depending on the usage, that might be a very useful factor for some devices.

Do we have a list of modules/receivers that are capable of providing a combined PPM stream out, in that from what I have been reading, it's very easy to process the entire stream on the Arduino, and I have interest in that direction

On the other side of the coin, are any of the modules we're using sending the data digitally, rather than using time based pulse transmission, or is that still a step too far down the road? Thinking aloud, I suspect that this is more Zigbee type territory. Any other options in this area?

Thanks
Irish Steve

If it was easy, shure, would't we all be doin it?

_
User avatar
jhsa
Posts: 19480
Joined: Tue Dec 27, 2011 5:13 pm
Country: Germany

Re: FRSky changing Firmware for CPPM length

Post by jhsa »

You have the PXX option, which is digital connection between the 9x and the module.. But it seems that frsky it's still developing it. Maybe we will have it fully implemented as soon as frsky releases their radios..

João
My er9x/Ersky9x/eepskye Video Tutorials
https://www.youtube.com/playlist?list=PL5uJhoD7sAKidZmkhMpYpp_qcuIqJXhb9

Donate to Er9x/Ersky9x:
https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=YHX43JR3J7XGW

User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

Irish Steve wrote:Ok, that sounds encouraging, now, living dangerously, would that mean that if the PPM output were to be fed to another processor, which is what's normally happening, a 27 ms refresh rate would allow more channels to be packed into the packets.
Yeah, a 27ms frame could safely hold 10 channels.
Irish Steve wrote:Clearly the standard 8 channel RX can only deal with the 8, but if I read it right, something like a small Arduino would be able to decode the "extra" channels and output them as either servos or digital channels. Depending on the usage, that might be a very useful factor for some devices.
Yep, but as the current frsky protocol only sends 8 channels over RF... the CPPM output still only holds 8 channels.
Irish Steve wrote:Do we have a list of modules/receivers that are capable of providing a combined PPM stream out, in that from what I have been reading, it's very easy to process the entire stream on the Arduino, and I have interest in that direction
FrSky D4R-II and D8RXP (8CH), TFRSP (for Futaba TX modules, 9CH), Graupner HoTT system (12CH), Jeti system, most 433MHz/868MHz long range/FPV systems,...
Irish Steve wrote:On the other side of the coin, are any of the modules we're using sending the data digitally, rather than using time based pulse transmission, or is that still a step too far down the road?
S-bus enabled receivers send the data for all channels as a digital serial stream.

The upcoming PXX protocol is supposed to offer the standard R/C uplink (16 channels), plus a secondary, bidirectional data channel. Now we still have to wait to see how they implement that.
User avatar
janekx
Posts: 90
Joined: Thu Aug 09, 2012 4:08 pm
Country: -
Location: Czech Republic

Re: FRSky changing Firmware for CPPM length

Post by janekx »

Few weeks ago i ask frsky for firmware if cppm is still beta they answer me to flash the fw but warn me to use max 6channels in CPPM.


Odeslano pomoci Tapatalk, Samsung mobile
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

The new one I tested fixes that and is OK with 8 channels. It works fine :)
User avatar
janekx
Posts: 90
Joined: Thu Aug 09, 2012 4:08 pm
Country: -
Location: Czech Republic

Re: FRSky changing Firmware for CPPM length

Post by janekx »

Where can i find this new safe FW?

Odeslano pomoci Tapatalk, Samsung mobile
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

Not released yet, still in testing.
User avatar
janekx
Posts: 90
Joined: Thu Aug 09, 2012 4:08 pm
Country: -
Location: Czech Republic

Re: FRSky changing Firmware for CPPM length

Post by janekx »

Better choose in dev fw than flight with danger one

Odeslano pomoci Tapatalk, Samsung mobile
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

Well... at least with the current firmware you know it's OK as long as you only use 6 channels. With the new one 8 channels are ok, but there might be other bugs we don't know about yet ;)
User avatar
janekx
Posts: 90
Joined: Thu Aug 09, 2012 4:08 pm
Country: -
Location: Czech Republic

Re: FRSky changing Firmware for CPPM length

Post by janekx »

Didnt found any problem with 4channels fot control and 4aux swiches but who know

Odeslano pomoci Tapatalk, Samsung mobile
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

It all depends on the position of the controls, and on the device you feed the PPM signal to. If you have all 4 switches on at the same time (+100%) and then give stick inputs that are too high, your device could lose sync.
User avatar
janekx
Posts: 90
Joined: Thu Aug 09, 2012 4:08 pm
Country: -
Location: Czech Republic

Re: FRSky changing Firmware for CPPM length

Post by janekx »

Tryed on kk2 but it is horrible board now prepare criusAIOP will be needed change frame time in multiwii if will change 18to27ms? Or it send frame width ?

Some release date?

Odeslano pomoci Tapatalk, Samsung mobile
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

I don't know, never used multiwii. All the FCs I know take whatever comes in without adjustments needed as long as it's valid.
renatoa
Posts: 9
Joined: Sat Oct 13, 2012 8:33 am
Country: -

Re: FRSky changing Firmware for CPPM length

Post by renatoa »

The 27ms firmware is now official:
http://www.frsky-rc.com/download.asp?id=23
User avatar
GTiDon
Posts: 177
Joined: Wed Mar 28, 2012 6:15 am
Country: -

Re: FRSky changing Firmware for CPPM length

Post by GTiDon »

Any instructions for Flashing this to a D8R 2Plus? and which pins to jumper?
Er9X Flashed
Speaker Mod Done
Haptic Feedback Mod Done
Telemetry Mod Done with FRSky TTL Lite
Voice Mod Done with Emartee Board
HK Backlight Done
FRSky Telemetry DIY Module Installed
----All these mods removed and installed Sky 3.0 board with DJT Module.
User avatar
Kilrah
Posts: 11108
Joined: Sat Feb 18, 2012 6:56 pm
Country: Switzerland

Re: FRSky changing Firmware for CPPM length

Post by Kilrah »

Same as for the D8R-XP. The hardware is identical.

Post Reply

Return to “The FRSKY Forum”