Devo 12S DSMX Range and Telemetry Questions

Hoping someone finds out whats wrong. Currently this is the reasin for me waiting to upgrade from spektrum dx6i to devo 12s.

I have alot of blade helies and a plane with spektrum reciever in it so need dsm2/dsmx to be solid.

Ground range is a good practical test.

150m at 100mW (+20dBm) with 2 dBi antennas, probably close for dipole, should produce a receiver signal of -57dBm.
www.pasternack.com/t-calculator-friis.aspx

The spec for the Cypress chip www.cypress.com/?docID=48819
claims ~ -80dBm for GFSK modulation, with no attenuation set, and (internal) LNA turned on. That should be 2000m!
An external LNA is very common, so this number could very well be ~20dB better.
If the receiver software control does not turn on full sensitivity, (page 9) then of course the numbers change, up to 50dB worse. (fig.11)
The SPI-bus data to the chip may be analyzed for this condition.

Other than device performance, the signal could get screwed up by other means, where antenna placement may be chief culprit; keep the last 2-3" of antenna well away from metal and CF. Pointing the TX antenna straight at the RX will reduce the received signal, as these antennas are mostly 1/2 wave dipoles, and should be at 90° to the RX, unless the TX box is conductive these antennas should be internal, like some Futaba TX. Buyer resistance may be the cause of the external 2.4GHz antennas, or marketing prejudice.
www.antenna-theory.com/antennas/halfwave.php
The TX power settings may be correct, but should perhaps be measured before we get too comfortable with assumptions.

An SMA to u.FL adapter should be used to measure conductive results thru normal RF-attenuators, to eliminate antenna causes etc.

The RSSI value from the SPI bus data can be extracted to measure receiver performance.

johnho100 wrote: Hi Everyone,

I tried to do a range test, I turned the transmission power of my 12S down to 100µw and at about 10 meters away, I already had over 100 FadesA and FadesB , 40 Loss and no Holds.
When I reached about 13 meters, FadesA and FadesB shoot up to 255 (maximum that could be displayed?), 200 Loss and no Holds. If I walked any further away from that, I got Holds and the telemetry module lost connection.

Most of the times fades are smaller than 80.
But on DSMx the number alone tells nothing.

Surely 40 framelosses are wrong.
Ground range test with reduced power MUST NOT show that high framelosses.

Coming from a Spektrum DX8 where I tried rangetest with TM1000 I can tell you that it is not normal to have 40 as F. I had that once with a faulty HF-module.
With a AR6210 and about ~60m away I almost had no framelosses (0 or minor numbers) in rangetest mode.


www.deviationtx.com/forum/protocol-devel...port?start=100#26681

255 is currently hard-coded in DeviationTX V4.01 + Nightly-Build (default).
This applies to fades as well as framelosses and holds.

For higher RX (7-8CH++) fades can be higher than 255.
AR6210 max bit counter is set to 255 / 0xFF.

johnho100 wrote: So my questions are:

6.) What is the proper way of range testing a Deviation Tx? Am I right to assume similar procedures to other brands Tx? Turn the power down to 100µw and walk 30 meters away from the aircraft, and if I still have full control, then I am good to go?

I am not sure if 100µw is mapped to Spektrum transmitter half range power??
Can you really choose 100µw when you walk away 30-35m or even 60m?
Would it require more tx power?
I read in another thread somewhere that the suggested rangetest mode was 100µw??

I fixed DSM telemetry flightlog in nightly-build / default locally so I may be able to make some tests with Devo 10 + AR6210 + AR600 + AR8000 in the next weeks/months.

a dump question, how can I switch DSMX telemetry on/off?

cmPang

Long Pressing protocol (DSMX and DSM2 as well) button gives no response. I can do that for Devo protocol and switch telemetry on/off..

My Tx is 7e on version: devo7e-v4.0.1=92e1705

For information, I experienced several bitter occasions that no RF power output while using Devo and subsequently discovered that I have left telemetry function ON. After switching back to OFF and everything went fine thereafter..
Now I get some DSM2/X receivers and found strange behaviors after binding with Deviation, so I would like to know how to switch OFF telemetry for further testing..

BTW, what is the default telemetry status? I've checked the model.ini and found unlike Devo, telemetry for DSM2/X not being specified..

cmPang

Sorry for my english...

With my Devo 8s at 100uw and a Devo rx702 i can't go more than 20 meters. After that i begin to lost signal.

It is ok?

I bought this radio because i love deviation and i will use this setup for my Trex 500l Dominator but if there are some danger with the range.....

For now it's winter here. at summer i make other test at full power.

Thank you!
Fred.

At 100uw (microwatt) I'm surprised you can get more than 5 meters. At 100mw (milliwatt) you ought to be able to go well over 100m.

I select 100uw when I'm doing bench testing to keep RF and battery drain down. When I fly I use 100mw or 150mw. Sometimes I forget to change and takeoff with 100uw -- I usually don't get more than a few feet away before it starts cutting out.

there leaves too much uncertainities in dsm2/x. Devo is trust worthy as long as telemetry is OFF.
Sure to have output cut out about once every say, 100 minutes if telemetry is left ON

cmpang wrote: there leaves too much uncertainities in dsm2/x. Devo is trust worthy as long as telemetry is OFF.
Sure to have output cut out about once every say, 100 minutes if telemetry is left ON

Hi cmPang,
are you sure, your issue is related to DSM protocols?
I had similar issues with devo protocol a year ago.
See: V120d02s-V2 lost binding mid flight.

After exchanging the hardware-module in my TX, I never had a RF-cut-off.

I am new to dsm. However, with over may be 5000 flights ob Devo, I can assure you to get a rf power down problem if you leave Telenetry ON sooner or later. Not frequent to the least, I have experienced only three times so far and each caused a great pain. For obe time my new plane flew straight out to the sea. Then I run through many hours of continous radiation with rf monitoring with a spectrum analyser at home and able to reproduce the problem. So went through other series of tests with Telemetry OFF and everything went fine.

If you are not a frequent pilot and flying a mini heli then it may not be a concern. The same if you are flying a gps quad with fail safe go home feature. Absolutely No No No if flying any heli larger than 450.
So be alerted. Do turn Telemetry to OFF

cmPang

cmpang wrote: ... with over may be 5000 flights ob Devo, I can assure you to get a rf power down problem if you leave Telenetry ON sooner or later.
...
Then I run through many hours of continous radiation with rf monitoring with a spectrum analyser at home and able to reproduce the problem. So went through other series of tests with Telemetry OFF and everything went fine.
...
So be alerted. Do turn Telemetry to OFF

cmPang

Hmm,
this confirms V120d02s-V2 lost binding mid flight.

At the time I did many tests and was able to reproduce the issue with telemetry ON. - No issue with telemetry OFF
But, after exchanging the TX-module I was never able to reproduce the loss of binding anymore, regardless of telemetry ON or OFF.

This leaves the question whether this is a hardware or software (=deviation) problem.
- Have you done your tests with more than a single TX?
- With what firmware versions?

Greetings
Manfred

I'm not very good in english but if i understand carefully... I must turn my tetemetry off and there are no problem to fly my trex 500?

I'm a close 3d flyer. I never go far.

Thank you!
Fred.

to say it in another words, NEVER turn telemetry ON while you are flying your trex 500

cmPang

How to turn off?
The old way by pressing long ENTER at the protocol field does not work with my 7e and the nightly (v4.0.1-92e1705)

Adding "[protocol_opts] Telemetry=Off" neither.
Telemetry is still on.

with my 7e, I can turn telemetry on/off for Devo but not on dsm2/X protocol

that is why I have to leave my recent purchased dsmx receivers alone for the moment


cmPang

Yes, I was speaking about DSM2/X.
With Devo it works.....

but my Devo10 works. So there must be something wrong in the 7e coding..

I hope this can be fixed for 7e soon.
Otherwise I had to buy at least a RF module for my old Futaba or put the two rx into the bin and get a FrSky module with two rx.
A CC2500 may work but now I am more cautious.

Found this:

hardware.c/2014-05-21/
Allow use of txid override on Devo7e. Devo7e will always be in telemetry mode now