voltages inaccurate after ethos firmware update on Tandem X20

[gregg]

On my Tandem X20 I have just updated my ethos firmware, and also the TD RF module, so now my system info has firmware version 1.1.1 FCC and Internal module TD-ISRM FW 2.1.1 (FCC). Everything works fine, except the telemetry on my aircraft 3S lipo now states each cell is 4.2v when in fact the lipo has 3.7v in each cell (measured by a charger). I have checked this on several lipos.

The fw update was triggered by replacement of my RTC battery. The voltage on the RTC battery in system/battery is stated as 3.0v.

Prior to these changes, the telemetry voltages on the aircraft lipo always corresponded with readings on my chargers.

Any advice would be appreciated.

 

[gregg]

I should have mentioned I have an Archer R6 rx and use an onboard MLVSS sensor to provide data on cell voltage.

 

[HENNY]

I think you mean Transmitter firmware version 1.2.1 FCC.

When does this voltage measurement occur. When the battery is fully charged at the charger because then the cell voltage will be 4.2 volts. How are you measuring the cell voltage at the receiver, do you have a a FLVSS connected to S-Port at the receiver side plugged into the balance lead? The other way is to use the A2 pin on the white connector of the receiver with a resistor voltage divider network and this will then give you pack voltage. Do not connect the pack voltage directly to the A2 pin as you will damage the receiver.

Best to confirm battery or cell voltage when its connected to the model and switched on, use a volt meter to confirm the cell voltages with a multimeter.

3.7 voltage per cell is close to a fully discharged battery voltage.

Also I recommend you update the RF firmware to v2.2.0 as there are a number of fixes in this firmware.

Lastly, the RTC clock runs fast and the newest firmware allows you to fudge the RTC so it keeps good time.

 

[gregg]

re "I think you mean Transmitter firmware version 1.2.1 FCC."
No, I quoted from the tx system/info screen "firmware version 1.1.1, FCC.

the file I downloaded 2 days ago from the Frsky website was FW-X20-v1.1.1.zip, and after unzipping I placed the FCC version (firmware.bin) in the root of the SD.

Until the upgrade as you say the charged 3S lipos had each cell at 4.2v, and I fly till I get a warning when one cell falls to 3.6v. The 3 cells are monitored during flight with a balance lead plugged into a FLVSS connected to the S-Port. This worked flawlessly till the software upgrade, and the telemetry on landing agreed closely with the subsequent charger measurements of the cell voltages.

re "When does this voltage measurement occur." I take a lipo that is discharged, with each cell around 3.7v, and place it in the model with the balance lead in the rx smart port. The tx says the cell voltage is 4.2 v in each cell. I have repeated this in 2 models with similar rxs and flvss, with multiple discharged lipos, so I believe the problem is in the tx.

my Internal module TD-ISRM is FW 2.2.1 (FCC), not TD-ISRM FW 2.1.1 (FCC) as I mistakenly said. Before I upgraded this int. module software the problem was the same, I did this upgrade in the hope it would fix it.

Thanks very much for your help.

 

[gregg]

I am thinking I will delete the current voltage sensors I call c1,c2,c3 for the telemetry, and then "rediscover" the voltage data from the flvss and reset my alert for when they fall to 3.6. Is it possible that they are not now measuring the cell voltage as there is a change in the firmware with the update that handles these sensors in a slightly different way?

 

[HENNY]

The FRsky web site Tandem OS is very old. Get the current version from the Ethos web site here Its 1.2.1 FCC currently. https://github.com/FrSkyRC/ETHOS-Feedback-Community/releases.
I recall there were a number of fixes relating to FLVSS so upgrade to transmitter firmware and see what your results provide.

Yes the RF firmware is now at v2.2.1 , it is found on the FRsky web site as you indicated.

The FLVSS monitors the voltage at approx 1 sec intervals. Measure the cell voltage at the balance lead while connected to the operating receiver, then you can be sure of what the FLVSS is reporting.

 

[gregg]

I just updated my firmware, system info fw now reads 1.2.1, FCC. Unfortunately the problem remains, eg I plugged a discharged lipo into the model and telemetry reports it as 4.2v per cell.

Early this morning before the 1.2.1 update I did a long flying session with 2 models, and the telemetry is reporting the 3S lipo cell voltages as 4.2 in each cell, before the flight, during the flight and on landing. Otherwise the radio and models are flying/performing normally.

Later today I will delete the current voltage sensors I call c1,c2,c3 for the telemetry, and then "rediscover" the sensors. I have an idea there may have been a change in how the cell voltages are handled and named by the firmware.

 

[gregg]

On page 179 of

X20 and Ethos User Manual_1.1.1_rev2.pdf

It states "1. How to set up a low battery voltage warning
In this age of telemetry, a better battery management approach is to monitor the battery voltage under load, and raise an alert when the voltage drops below the chosen threshold. For this a battery voltage sensor such as the FrSky FLVSS can be used.""

This is what I am now trying to achieve and I already had it working perfectly prior to my fw update. The manual says I will see the sensor in the telemetry screen (shown on page 179, the sensor called "Lipo 2.4G""). When I try to discover my voltage sensor (Frsky MLVSS), I do not see this when I "discover new sensors".

p 179 states you should "In Receiver Options set the Telemetry Port to the S.Port option." Here is where I fall down, because after an hour of searching I cannot find "receiver options" either in the manual or the X20. If someone could point me to where "receiver options" reside I will be grateful. If you want to set the Telemetry port, would it not be sensible to do this from the Telemetry menu, or at least show what port is currently selected, or if redirection is needed to tell the user under what menu the "receiver options" reside?

I believe the tx knows about the MLVSS because when I remove the balance lead from it I hear "sensor lost".

this is becoming long-winded.....

 

[gregg]

I found receiver options. See p88 of the manual. Under model/RF system there is a line
RX1 R6 Bind Set Reset.
(my rx is an Archer R6)
When I click Set I get "Options" and there is an item "Telem port". My rx was set to F.Port, so I changed this to S.Port. However when I went back to discover new sensors in Telemetry, there is still no evidence of Lipo 2.4G or any voltage measures from my MLVSS. Yet I emphasise that before I updated Ethos as described above the telemetry from the lipo/ MLVSS sensor was working properly giving audio cell voltages either by a momentary switch, or if a cell dropped below 3.6v.

 

[gregg]

This morning I checked under model/RF system, RX1 R6 Bind Set Reset, that when I press 'set' the telem port is still set to S.port. I then did a another bind of rx1. Still the lipo voltages do not appear when I turn on discover new sensors in Telemetry.

 

[HENNY]

This morning I checked under model/RF system, RX1 R6 Bind Set Reset, that when I press 'set' the telem port is still set to S.port. I then did a another bind of rx1. Still the lipo voltages do not appear when I turn on discover new sensors in Telemetry.

The connection from the FLVSS to your receiver needs to be connected to the S-Port on the R6 using the white connector, and not to the S-bus pin. Use the little cable with the servo connector to connect this between the FLVSS and receiver, the S-port is the yellow wire. The red led on the FLVSS should be blinking, make sure you connect the servo plug on the FLVSS the correct way. Also connect the bind cable to the FLVSS the correct way and to the correct end of the S6 FLVSS connector. It does work unless you have damaged something.

 

[gregg]

I finally worked out how to get "lipo" to appear in the telemetry screen. Telemetry has a "delete all sensors" command, and when implemented the telemetry screen shows no sensors or system values. Then press "discover new sensors" to ON, and hey presto all the sensors appear including lipo (correctly displaying a value of 11.2v of a discharged 3S lipo). I have not yet set up monitoring of individual cells but from this point the setup looks straightforward, following the manual from p179 onwards. I can now set up the voltage monitoring on 5 models that were affected by the firmware update.

re "The connection from the FLVSS to your receiver needs to be connected to the S-Port on the R6 using the white connector, and not to the S-bus pin."

This is how I have it on all my models with the MLVSS sensor. My problem was not with the connection, but occurred because I did not understand that the FW update messed up the MLVSS sensor telemetry, and the only way to fix it is to delete all sensors and re-configure them.

 

[HENNY]

OK, great out come for you. Glad we could help.
Henny

 

[gregg]

I now have the in-flight lipo voltage monitoring working on all my 5 planes with an MLVSS sensor ... thanks very much for the help