PXX work

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Re: PXX work

Post by MikeB » Wed Sep 11, 2013 2:44 pm

There is a small gain as it only takes about 3mS to send all 8 channels to a XJT module using PXX instead of the full (up to 16mS) the the channel data of a PPM frame.
My current implementation is sending this every 18mS.
I'm trying to get test versions, with PXX for the XJT, ready to post.

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Re: PXX work

Post by tilmanb » Sun Sep 15, 2013 11:26 am

Am I right in assuming that PXX is bi-directional?
Or is there still a separate serial line for telemetry with the new Taranis modules (XJT or internal)?

I would even thing that PXX and S.Port are electrically the same?

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Re: PXX work

Post by MikeB » Sun Sep 15, 2013 11:37 am

They are separate. PXX is for the control data to the module, one direction only. The SPort is bi-directional for both receiving the telemetry data and sending commands to the sensors on the receiver.

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Re: PXX work

Post by tilmanb » Sun Sep 15, 2013 3:33 pm

Thanks

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Re: PXX work

Post by volumax » Thu Feb 13, 2014 6:30 am

This thread has gone stone cold, any new updates on PXX?


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Re: PXX work

Post by Kilrah » Thu Feb 13, 2014 8:59 am

It's been implemented in all versions of ER9X and on the Taranis version of OpenTX months ago. Other boards for OpenTX still pending. It's only supported by the new XJT module.

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Re: PXX work

Post by jhsa » Thu Feb 13, 2014 9:42 am

Kilrah wrote: It's only supported by the new XJT module.
What a shame, Frsky told me they would release an update for the D series modules a while ago.. But obviously they didn't say when.. So, I wouldn't count on it as it could be tomorrow or in 30 years.
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Re: PXX work

Post by volumax » Fri Feb 14, 2014 7:39 am

Do you guys know if there will be any FW updates for model match on non-x8 receivers? I really like that feature and would be nice having it. Another thing, you mention update for the D series, didn't Mike have his DJT working with PXX?

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Re: PXX work

Post by jhsa » Fri Feb 14, 2014 7:46 am

Yes he did. When pxx was being developed.
I won't buy receivers for all my planes a second time, so if they don't release an update for the module and.probably receivers, I will stock on D series receivers before they disappear. I guess that as soon as all the x series receivers are being produced they will discontinue the D series.

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Re: PXX work

Post by volumax » Fri Feb 14, 2014 8:32 am

I actually need PXX for helicopter flying, Kilrah informed me of the latency advantage I would obtain which is great. Do any of you know whats the latency on stock 9x transmitter? Maybe I should just chase a taranis down and get full advantage.

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Re: PXX work

Post by MikeB » Fri Feb 14, 2014 9:57 am

er9x supports the XJT module (using PXX). This supports using 'D' series receivers, while still using PXX to 'talk' to the module.

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Re: PXX work

Post by jhsa » Fri Feb 14, 2014 10:00 am

Yes Mike, that is great. but it would mean scrapping the 3 modules I already own and buying new ones.. it would be nice if we could update them.. :)
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Re: PXX work

Post by volumax » Fri Feb 14, 2014 10:41 am

I have a XJT which "works" on PXX with V8RF-II receiver. Do you mean I wont have the latency advantages of PXX with this receiver?

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Re: PXX work

Post by Kilrah » Fri Feb 14, 2014 10:54 am

As long as you have an XJT and it is driven by PXX you have the latency advantage with ALL compatible receivers. What you don't have with a V8FR-II or D series is model match and remote failsafe setting as that only works in D16 mode (with X series receivers).

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Re: PXX work

Post by volumax » Fri Feb 14, 2014 11:58 am

Ok thanks again Kilrah for confirming that, do you know what the latency is on a stock 9x and the the latency on a 9x with er9x running pxx?

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Re: PXX work

Post by Kilrah » Fri Feb 14, 2014 12:09 pm

Test I had done with an FrSky module with PXX vs PPM showed it was about halved (~30ms instead of 60ms).

No idea about the stock FlySky module.

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Re: PXX work

Post by MikeB » Fri Feb 14, 2014 12:14 pm

I think I need to do a change at some point. I'm sending 16 channels over PXX. I should probably send only 8 channels if in D8 mode.

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Re: PXX work

Post by volumax » Sat Feb 15, 2014 4:46 am

Would that lower the latency even more Mike?

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Re: PXX work

Post by MikeB » Sat Feb 15, 2014 10:35 am

Most likely, 8 channels are sent to the module every 9ms. In D16 mode this alternates between channels 1-8 and 9-16. In D8 mode I'll always send channels 1-8, so the latency should reduce (by 9ms I think).

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Re: PXX work

Post by volumax » Sun Feb 16, 2014 5:54 am

I will test one of my helis in PXX and see the difference, I hope you can make those changes Mike, lower latency is almost a must when you are trying 3D.

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Re: PXX work

Post by volumax » Mon Mar 17, 2014 9:57 am

MikeB wrote:I think I need to do a change at some point. I'm sending 16 channels over PXX. I should probably send only 8 channels if in D8 mode.

Mike.
When I do D8 mode I would only use 8 channels, am I correct? Do you see yourself doing this change soon?

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Re: PXX work

Post by Rob Thomson » Mon Mar 17, 2014 10:29 am

D8 MODE is needed for all older D series receivers.

You are limited to 8ch.

If you gave he new receivers... You can use up to 16.

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Re: PXX work

Post by MikeB » Mon Mar 17, 2014 12:03 pm

volumax wrote:Do you see yourself doing this change soon?
The change for D8 mode is in for the next revision. A test version of th next revision is here: viewtopic.php?f=5&t=4598#p64969.

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Re: PXX work

Post by FlyByTheGrace » Wed Mar 19, 2014 4:59 pm

Hi Guys,

I am trying to set up my 9x at present for use with my Quad and APM 2.5 FC.
I am running Er9X FrSky NOHT r809
I have just become aware of PXX. I have tried to read thru the various posts about it but I am not getting it. What does it do???
The unzipped PXX file and there are two files in it,

>>fdd_tx_rev2_build110314.frk<< for the Rx, and >>er9x.frk<< for the Tx module correct?
At present:
I have no need of more than 8 channels at present though I would like to have my D8RII+ outputting cppm so that there is only one signal wire connecting the Rx to the FC to cut down on possible vibration transmission but of course that involves FW meant for the XP and then there is D8R-XP_CPPM_27ms for that.
So how does PXX fit into the picture? Perhaps it is bit too advanced for my current experience level, I am not sure....

I am conversant in using my FTDI to flash both my DJT and D8RII Plus and I thought I was up to date.
I have completely upgraded my 9X with the SmartieParts SPB the TelemetrEZ module the backlight and I am about ready to install a six position switch to try a different way of arriving at Flight Modality in Arducopter

Would somebody be so kind as to give me the low down on PXX?

>>>EDIT from an hour later>>>>>Found this quote on another thread for "New in ER9x and eePe" It's essentially a PCM code that allows for advanced functions like Model Match, More than 8 channels (you can transmit to as many as 125 different rx at the same time!), low latency and failsafe."
Could someone explain model matching and and the difference in the latency it affords one. And the bit about the Failsafe matter" EDIT<<<

Thanks and Regards to all
Chris

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Re: PXX work

Post by MikeB » Wed Mar 19, 2014 7:20 pm

PXX is used by the XJT module and most of the gains are only available if you also use a X8R receiver. FrSky were supposed to be providing firmware for the DJT module to support PXX, but it didn't happen.

So the quick answer is PXX does NOT work with a DJT (or DHT) module. You can use a XJT module with a D8RII Plus, and use PXX as the protocol to the XJT module, but the D8RII Plus cannot do model match etc. You would gain in latency as er9x sends control data to the XJT every 9mS, instead of a PPM frame of 22.5 mS.

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Re: PXX work

Post by volumax » Sun Mar 23, 2014 8:01 am

So Mike with this test version we are supposed to have a latency of 9ms?

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Re: PXX work

Post by Kilrah » Sun Mar 23, 2014 8:24 am

Refresh rate, not latency.

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Re: PXX work

Post by Iksbob » Mon Mar 24, 2014 2:03 pm

Kilrah wrote:Refresh rate
... Which affects latency. Latency is the time delay between moving a stick on the controller, and the corresponding servo(s) moving on the model... End-to-end lag. Refresh rate is how often updated channel-state information is sent from the transmitter CPU to the receiver CPU over the radio link. Since channel information has to wait for its turn in the update queue (which is sent out every 9ms in this case), refresh rate plays a significant role in latency but does not represent the entire value of latency. There are additional delays (latency) in the radio firmware (openTX, er9X, etc.), data processing in the TX module and RX hardware, decoding by the RX CPU, and even from the drivers in the individual servos or ESCs. Reducing delays in any of these areas will improve overall latency, though depending on the other components in your system (such as analog servos, which update every 17ms) such improvements may not be apparent.

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Re: PXX work

Post by Kilrah » Mon Mar 24, 2014 5:16 pm

Yes of course, but he said 9ms latency, which is why I corrected. Most people confuse the 2 and when they read 9ms frame rate they think end to end latency is 9ms.

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Re: PXX work

Post by volumax » Mon Mar 24, 2014 8:13 pm

So do you guys have any idea what the total latency would be using the XJT module on PXX with the changes Mike did on er9x?


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