Multiplex evo RFU and telemetry - RC Groups
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Feb 11, 2018, 12:37 AM
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Multiplex evo RFU and telemetry

Jim or others,
i only found a 2013 post on Evo and RFU telemetry. didn't recently indicate that i should be able to use telemetry now with RFU and Evo FW 3.x?
is there any description how to accomplish that? do i need extra sensors in the plane or can i get back battery voltage at receiver etc?
thanks Erhard
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Feb 11, 2018, 11:45 AM
There are threads on enabling telemetry, which has to be done in the RFU itself (the manual also has info).

With the RFU you can get back signal strength (RSSI) and the input voltage to the RFU. You would have to build your own sensors, and we have schematics, PCB artwork, and source code available for doing that. Some people have built things like quad voltage sensors for various power sources, RPM sensors, and temp sensors. Originally, you needed our Telemetry Station to get this data. However, with the Auroa 9 and EVO (with v3.0 or later firmware), you can get telemetry data in the transmitter's display.
Feb 13, 2018, 11:37 PM
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ok i enabled it on the RFU and read at home:
0: 100% LQI
1: 5.4V
6: 0m1

does this make sense?
and what do the values mean? besides the 5.4V which seems to be the receiver voltage
Feb 14, 2018, 12:00 PM
100% LQI is the signal strength. LQI is actually the Link Quality Indicator. It will give you a 0% to 100% value depending on the signal strength and packet loss (both are factored into LQI).

The other values don't have valid values because there are no sensors for them.
Feb 15, 2018, 01:41 AM
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i like the packet loss - so is there then a number where i should be worried, or can it be used for the range test?
also i thought the 5.4V is the valid receiver voltage
thanks Erhard

just tested
voltage reported as 5,4V but measured at X10 as 5.56V
when turning on RANGE TEST on EVO the LQI immediately falls down to 70-60% when about 3m away (sorry small home
otherwise at 100%

oh forgot to ask
when telemetry is on , it does NOT compromise the actual radio link?
Last edited by schrecke; Feb 15, 2018 at 01:48 AM. Reason: added data
Feb 15, 2018, 01:51 AM
Registered User
where can i find the info for hardware and firmware specs to add telemetry sensors?
are there commercial sensors compatible?
Feb 15, 2018, 09:17 PM
You want LQI above 0%. I don't where the limit is with the EVO. The LQI will definitely fall when you are in range test mode, the power goes from 100mw to .019mw!

There are no commercial sensors compatible. Our website has the technical data for building sensors:
Feb 15, 2018, 09:43 PM
Registered User
thanks Jim
ok i did some flying with telemetry enabled. here some feedback.

during flying (2.6m sailplane high up) the LQI varied between 89 and 92% - the update seemed to be slow like in 10 or more seconds. is that controlled by the EVO or the RFU?
when i went in to range test mode the signal went to 50% LQI minimum. at this levels i could either have still control or not- also turing myself around 360 did not change the LQI reading - again this could be an issue with the update speed. so the LQI itself does not seem to be a good indicator if the radio link still works or not.
not sure if other people have done more testing on that subject
Feb 16, 2018, 07:11 PM
The LQI most certainly does show the link quality. The update rate can be set by the RFU, using the XDP, but the default rate is 10 times per second. So, it is basically real-time.

I know for experimenting that you still have good control with a LQI of just 10%. However, this was with the original v3.0 firmware. I don't know if that has changed. I don't think I used the rang test mode to determine that. I believe I unscrewed the antenna (with full power) and just walked away from the model.
Feb 18, 2018, 11:28 PM
Registered User
i played out in the field somewhat more with the LQI reading and conclude that it is not very useful - sorry.
with plane slightly elevated on ground i walk away and watched control surface and LQI. the LQI number changes only very infrequently. starts at 100% when close and when it went to 70 i already lost control. also changing direction of TX antenna has no affect on LQI but on actual radio link. all i see when plane is in the air it is usually in the high 80's. just my experience with the EVO.
Feb 19, 2018, 01:32 AM
That's definitely not my experience. I used the LQI for testing our Nano antennas and changed the length based on the LQI results. You shouldn't lose control until the LQI is 0%. You have to use full power to get telemetry info. Telemetry info is not updated when the power is reduced (range test mode). I unscrewed and removed the antenna for testing.
Feb 19, 2018, 02:23 PM
Registered User
the above described experiment was done with FULL power mode (no range test). I assume you used your telemetry module for your testing. like i said that is what i got with my EVO. i am also wondering what is the range of the telemetry link. is it same or better than actual radio link. ideally it should be better and it could because it could use lower bandwidth.
yes i would have expected to see orientational sensitivities of the antenna directions - kind of dipole radiation field but, to my surprise, i did not. anyway thanks for your response.
also curious have you tested LQI with for example dual RFU reception - is it better?
Feb 19, 2018, 05:59 PM
I used the EVO for testing. Fully power, antenna removed. Walked away from the receiver to check LQI. Lost control somewhere between 0 % and 10%. You should always have control when the LQI is greater than 0%. If the EVO is in range check mode (reduced power), the LQI information is NOT updated at all by our module, so it won't be correct.

Keep in mind that LQI is not the same as RSSI. LQI combines the number of successful packet with the overall signal strength. RSSI is technically better for tuning antennas, checking installations, and such. I used our Telemetry Station with special software to verify the results shown by the LQI.

With multiple receiver setups (like with the X10+ or X24), the receivers are checked in order (primary/secondary for the X10+ and 1/2/3/4 for the X24). Whichever receiver has valid data first is used. With 2.4GHz systems you either get 100% good data or no data, so it's easy to just go down the line of receivers and use which ever has data.
Mar 06, 2018, 09:29 PM
Registered User
may be you can give me some more information on the telemetry. obviously you managed to use the proper protocol to the Evo understands the LQI. so if i would connect a multiplex sensor would that not work over your Bus system, spectrum talks about x-Bus, is there no industry standard?
Mar 07, 2018, 12:27 PM
There is no standard. Every company has their own wiring, logic, and protocols.

You can't just use a Multipex sensor because it's an XPS protocol that gets converted to the Multiplex protocol.

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