PXX work

[pmackenzie]

I agree - perfect example of a solution in search of a problem

[MikeB]

I'm not sure the bus idea for servos actually works well. I did something like a bus when originally wiring up the wings of my Mosquito. Each wing has throttle(opto esc), aileron, flap and retract servos. I used a computer 9-way D-type in each wing, with large power and ground wires and several signal wires. The flaps would glitch badly when other servos were operated, particularly on 35MHz FM. 2.4GHz is better, but I separated the flaps from the D-type, and ran separate power and ground to each servo and esc. I have some 15-way D-types I shall use, but will still keep all the servos separately wired.
It was also a problem when I tried running from a U-bec, I now use a separate 4-cell pack of AA NiMh, 2000mAh, and rated for 25A discharge, all glitching has now gone.

Mike.

[android78]

I'm not sure the bus idea for servos actually works well. I did something like a bus when originally wiring up the wings of my Mosquito. Each wing has throttle(opto esc), aileron, flap and retract servos. I used a computer 9-way D-type in each wing, with large power and ground wires and several signal wires. The flaps would glitch badly when other servos were operated, particularly on 35MHz FM. 2.4GHz is better, but I separated the flaps from the D-type, and ran separate power and ground to each servo and esc. I have some 15-way D-types I shall use, but will still keep all the servos separately wired.
It was also a problem when I tried running from a U-bec, I now use a separate 4-cell pack of AA NiMh, 2000mAh, and rated for 25A discharge, all glitching has now gone.

Mike.

So was the glitching from an unstable voltage on the power to the servos due to resistance in the wires, or problem with the channel identification?
I was thinking of a simple circuit using 4516 counter with PPM for clock and using the overflow ANDed with the PPM for the output. This would have a simple R/C and transistor for the reset to identify the start pulse, and hard wire the preset for the channel that you want to use. I would also hard wire it in count down, so that the preset is a +ve channel number. This would be a very simple circuit and negligible weight addition, but I guess the stability of the power could be an issue, but a capacitor on each servo could help with this. I wonder if digital servos would be much better for this? Maybe not a lot since it will still be using an analogue comparator against the pot for detecting the position.
Something to think about though.

[pmackenzie]

In my 4 servo glider wings I use 15 pin D-subs so that I don't have to share power and ground wires.
It is also easier to solder up, since the D-subs are not really designed to take more than one wire per pin.

DLGs on the other hand with 2 servos in the wing share the power leads, so only 4 pin connectors are used.

Pat MacKenzie

[somebuddy]

hey

What about PXX and the DHT module ?
Is there a possibility to flash the DHT Module with the pxx firmware ?
I've only read DJT etc. modules.

Thx !

[MikeB]

As far as I know, the tx modules use the same firmware so I would assume it would be fine. As long as you can flash the module, you can always put a non-PXX version back on anyway.

Mike.

[jhsa]

I think the DHT it's just the same as the DJT but without the case.. I'm waiting for a new tx and also ordered the DHT..

[MikeB]

Indoor flying again, this time one model was using PXX, no glitches, just worked.

Mike.

[cre8tiveleo]

Noice!

[erazz]

No word fro FrSky yet...

They seem to be really interested in S-Bus. I personally think it's a poor move. S-Bus is propriatery. I haven't seen the protocol itself but I'm willing to bet that it's not as expandable and versetile as PXX.

I have some neat ideas to do with PXX that will be awesome. Waiting for answer from FrSky to continue.

[Kilrah]

There's some info there:
http://forum.mikrokopter.de/topic-16535.html

IMO they probably have interest in S-Bus as it's the only "digital" protocol for which there are servos out there today, would be a great selling point for them, "use your S-Bus system with a receiver that's 10 times cheaper"... ?

[erazz]

Ugh... German. No offense but it's Chinese to me

Is there any description of the SBus protocol itself there?

[Kilrah]

No, but code to translate it into PPM... which should be a language you understand

[erazz]

Yeah, I saw that... Gave me a headache. I'm just lazy, looking for an easier way out

[Kilrah]

More detailed S-Bus description (still in German though ), very easy. 100kbps 8E2 UART comms, one start byte, 16 11-bit channels concatenated to form 22 bytes, one byte with flags, one stop-byte. There's also the info how to set the servo's channel number.

http://www.flightronic.com/index.php?pa ... -protokoll

[erazz]

Awesome

I'll tinker around with it and see if I can emulate it.

[Kilrah]

Cool!
Although it's pretty much designed to be used only on receiver-side AFAIK, so I wonder if there's any real interest to do something with it on TX side... or were you implying FrSky would replace their PXX protocol altogether with S-Bus also between radio and TX module??

[erazz]

They seem to be really keen on it. I simply want them to provide us a "remote pin". That is, have one pin on the rx mimic what it seen on the tx module.

It's simple to do but they are balking and I don't know why. I swear... I'm on the verge of ditching it all and building my own supercheap system. It's really not too hard.

[Kilrah]

Yep, but if that protocol has no support beyond the receiver, what's the point? There I can understand the desire to go with S-Bus, as there are existing accessories for it, some multicopter boards etc start supporting S-Bus,...

And replicating just about anything that is done on the TX module isn't that easy if you take into account RF framing, hopping schemes,... there has to be at least a canvas to stick to.

What they could do (wouldn't that actually already be the case? haven't tested...) is to leave the main R/C feed alone and dedicated to control (and use the existing multi channel protocols like PPM and S-Bus for interoperability reasons) and make it so that one could send data into the RS-232 port of the TX module and have it appear on the TX pin of the receiver, allowing you to pass every kind of data you want into that secondary feed transparently, just like for telemetry, to feed into your own decoder.

Oh well, an FrSky module is just an STM32 and a CC2500 RF transceiver - nothing harder to write an alternate firmware for than the 9x

[erazz]

All of these are "not hard" to reprogram in a sense that there are tools available and the schematics are out there.
Actually reprogramming them work properly isn't easy IMHO.

[shaddi]

Hm, yes. PXX on the transmitter-side and S-Bus on the receiver on a spare Pin could also be very nice. 16 Channels for all those Multirotor-Controller out there

[erazz]

Actually now we're talking about a SERIAL connection on the Rx side.....

[Clivew]

Hobbyking's finest(!) "Clouds Fly Floater Jet AXN" works perfectly with PXX also!
Nice little aeroplane too!

Indoor flying again, this time one model was using PXX, no glitches, just worked.

Mike.

[MikeB]

FrSky seem to be moving forward on PXX, adding:
Range check,
Bind,
Range check,
Rx type - non-telemetry, telemetry, 16 channel telemetry
Failsafe setting,
Model match.
All these selectable within the protocol, so no switch changing on the module needed!
Also seem to be suggesting they will be adding serial data transmission from tx to rx.

Just need some new code from them to load into the tx module, and possibly rx, to try some of this.

Mike.

[jhsa]

Nice, those are great news..

[Rob Thomson]

Swweeeeet!!


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[Crucial]

What is the current best way to update the frsky modules and rx's? I just bought a DJT and 5 rx's and will start switching over my radio this weekend.

[Rob Thomson]

You only need at this point to update the tx module.

Use the firmware erazz provided in the first few posts of the thread.

What you want to do is download an update firmware from the frsky site. This has the program and instructions on how to update it.

Only difference to the procedure is to select erazz's firmware.


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[Orphee]

Hi, dies it work for telemetry tx only ? I have a DIY V8HT non telemetry.
Frsky website is ko for me

[MikeB]

I believe it is only on the telemetry tx. I'm not sure if the V8 series firmware is upgradeable.

We are waiting for new firmware, to do the new stuff, from FrSky.

Mike.