Setting up telemetry on FrSky Taranis with D4R II receiver

One of the most useful features of FrSky radio would be telemetry. This radio protocol is used to transmit the in-flight data from the radio receiver to the radio transmitter (so literally you have a 2-way communication radio system).

D4R-II is a popular Frsky receiver often used in mini quads. It’s compact, light weight as well as having PPM and telemetry support.

Frsky Telemetry – RSSI and LiPo Voltage

FrSky telemetry has an impressive list of features and is capable of sending various types of flight information. As an example, we will show you how to set up telemetry to receive RSSI (Signal strength indication) and LiPo battery voltage readings, and display them on your TX screen.

Some might ask why use telemetry when Lipo alarms or OSD are available. Lipo alarm must be attached to the aircraft battery balance plug. If the quadcopter is a long way from you, you might not hear it when the alarm goes off. OSD is good, but having telemetry as well you have an extra layer of safety, not to mention it can warn you when something reaches critical level by beeping on the TX.

In this example we will use:

  • FrSky Taranis X9D radio transmitter
  • FrSky D4R-II radio receiver
  • Naze32 Flight Controller

Also check out this Taranis Custom Sound Track tutorial.

Connection Setup For Telemetry

In order to receive voltage information from the battery, Naze32 needs to get that information from the battery voltage monitor pins (VBAT) first.

According to the Naze32 manual:

“Optional Battery Voltage Monitor

To enable in-flight battery voltage monitoring and alarm, connect this header to flight battery or power distro board. Up to 25V (6S LiPo) can be measured. No reverse polarity protection – connecting battery in reverse will instantly destroy the hardware.”

Naze32 ports location required for telemetry

What we need is a servo cable and solder one end to the power distribution board or power harness. This connection will get voltage reading from the battery to Naze32. Correct polarity is very important here! You can also setup low battery alarm in Baseflight/Cleanflight, by enabling the VBAT feature, that’s how the Naze32 knows when to start the low voltage buzzer alarm.

D4R-II receiver has an external analog telemetry port. It comes with a cable composed of four wires – black, white, red & green (in this order).

FrSky D4R II telemetry port location

We will use black and green wire only, which is ground and RX. White and red are used for other telemetry information that is no relevant to our setup here. They can be removed completely ,cut short or simply folded for future use if you want. The D4R-II receiver comes with two sets of these cables: one with two male connectors, and other with just one connector and open end wires ready for soldering.

Connector cable

Green and black wires can be soldered to a servo cable with a female end, and that should be connected to the telemetry port on the Naze32. The very important rule:

  • Green wire goes to “+” on Naze32
  • Black wire goes to “-“ on Naze32

With all cables connected correctly, Taranis should be ready to receive Telemetry information from the RX. Note that Telemetry will only work when the board is armed.

Taranis telemetry screens setup

On the radio itself we need to go through the configuration setup in order to:

  • display correct voltage information
  • alarm on low voltage
  • warning on low RSSI signal.
  • display additional information (Altitude etc.)

On the Taranis, when we are in the model menu, it takes us to the telemetry screens by holding down the PAGE button. There are three screens and we can customize how the telemetry information is presented and displayed.

Telemetry screen 1
Telemetry screen 1 configuration
Telemetry screen 2: Bars
Telemetry Screen 2 configuration

In above examples I setup Screen 1 to show numeric values of Total lipo voltage level (Cells), Per Cell and RSSI Signal Strength. (Apart from telemetry, it’s also possible to get RSSI value via a spare PPM Channel)

Screen 2 was setup to show the same values but with a graph (bar chart). It has the low value set to 3.3V and high to 4.10 (which is 100% of the battery voltage). Tmr1 is a timer which is set to 7 minutes, which is my normal average flight time.

Parameters used in telemetry screens are:

  1. Cells – displays total voltage of the battery
  2. Cell – displays Cells divided by a number of battery cells.

Voltage level is detected by the Naze32 of the whole LiPo battery, so it is impossible to get voltage of each single cell. Cell value is used for setting voltage alarms on the radio.

Configuration can be done using radio screen or CompanionTX software (available to be downloaded on the OpenTX website), which allows you to upload settings to the radio from your computer. Setting it up directly on the TX takes longer, but you don’t need a computer. Using Companion app is much easier in my opinion, due to the nice and user-friendly interface.

Companion TX. Telemetry Screen 1 configuration
Companion TX. Telemetry Screen 2 configuration

A1 and A2 are the analog telemetry ports on the receiver. On D4R-II we are using A1. First we need to setup the range. The receiver’s maximum input voltage used for telemetry is 3.3V. Internal voltage divider is 4:1. Maximum voltage reading for A1 is 3.3×4=13.2. In my setup I use 13.3V as this is recommended. Detailed video on telemetry voltage calibration can be found here.

Low battery alarms are a matter of personal preferences. In general we don’t want the battery to go completely flat during flight so setting low alarm to 3.5V – 3.7V is sufficient. Use whatever values that you feel should give you enough time to fly back and land safely. Critical alarm means that at this stage, we need to land immediately, otherwise the quadcopter will be likely falling out of the sky due to lack of power.

Taranis telemetry “talking” voice setup

One great feature of the Taranis is the custom voice capability, you get a lovely lady voice talking to you. Taranis radio can return us the information by “talking” to us while we are flying, so we don’t need to look down on the LCD screen. We can configure the radio switches to report battery voltage, or configure it so it warns us when RSSI reaches low or critical level and so on.

My “talking” custom voice setup has three scenarios:

  • Taranis tells me when the battery voltage goes down below 3.44V.
  • After the board is armed, Taranis reminds me every 60 seconds what the battery voltage is.
  • When SH switch is toggled, Taranis tells me the current battery voltage.

In order to do that I set Logical switch L1 with value Cell set to 3.44V. In special functions I have created SF1 that is constantly looking if L1 switch is true to play the sound batlow (battery low).

Created also SF2 to tell me current voltage when switch SH is pressed down. Switch SF3 and SF4 are applying to my timer settings. Switch SF5 speaks voltage value every 60 seconds when arming switch, in my case SF was pressed down to arm the board.

Taranis Logical Switches
Taranis Special functions

30 thoughts on “Setting up telemetry on FrSky Taranis with D4R II receiver

  1. Leonardo Kamache

    Hi Oscar!

    It’s incredible that almost every search I made about quads and related stuff your blog always shows up!
    I have a simple question… I’m trying to see my battery voltage using a DJI Naza flight controller. Can I plug the green and black wires directly to my battery?

    Best regards and congratulations for your blog!

    Leonardo Kamache

  2. Kevin

    “Note that Telemetry will only work when the board is armed.”

    Oscar Liang , I was going nuts after waiting a month for parts and spending all day wiring up everything. I spent just as much time trying to get telemetry to work searching youtube. Now it works because of your blog. Now I love my Taranis =P

  3. VL


    Quick question, in the logical switches image, !L1 or L1 ?? Pretty sure it would be L1, but I haven’t had coffee yet.


  4. Gimpster

    Hi Oscar,

    Great basic overview of how to set this up. I like others struggled to follow this guild and get it all working. I just could not get the telemetry outputs/sensors to be detectable. Only the four basic sensors would display, RSSI ALT, A1 & A2. Last night I found a video, which showed the part nobody seems to talk about but in hindsight appears obvious. Here is the correct process, assuming you followed this guide and have it wired correctly and setup in the FC software to output telemetry.

    1. Power on the Taranis
    2. Power on the FC and connect the flight battery.
    3. Arm the FC. (This is the part no one talks about.)
    4. Navigate to Telemetry setup on the Taranis, clear all sensors and scan for new ones.

    If you don’t arm the motors all you get are the RX’s sensors.

    1. Csaba

      Hi Oscar

      Please help, how to connect FrSky D8R-XP telemetry port to flip32 flight controller ?

      How to jumper ? How to setup cleanflight ?

      ( flight controller link: )

      Thank you in advance for your help.

      Best regards,


  5. Nick

    Hi Oscar, I absolutely love your How-To’s, they have talked me through MANY parts of my project.

    The only thing I am having a REALLY hard time finding, is a How-To to connect the Naze32 Rev6 Full to an X8R. Do you have this walkthrough yet? Is this something you might be able to help with? I know there are many people in my shoes who would benefit from this one…

  6. Sid

    Hi Oscar
    I’m trying to read battery voltage by using FBVS-01 and I just don’t have any success on my Taranis radio. To begin with on my Telemetry screen I dont see any A1 or A2 screen and when I scroll down to screen #1 I can choose Batt on the 1st line and on the secound line I can not find Cells or cell at all. Is just not there. I have updated to latest 2.1.7 and still no luck.
    Thanks in advance

    1. madeen2

      i had it working on all earlier versions except 2.7.1. When going into inputs and editing source there is no option for RSSI. anybody else getting this issue?

  7. bbbd

    Hi Oscar
    Please can you refresh screenshots from the new open Tx 2.1?
    Screens are diffrent.
    Maybe you have found some tutorial in net with new opentx?
    thank you

    1. Oscar Post author

      i haven’t updated my Taranis firmware yet… i am not planning to do so because it’s working fine for me and I currently dont have time to do it… sorry!

      1. Dan


        I had Tx 2.1 firmware installed and had nothing but small issues (here and there). I went back to Tx2.0.19 but now my RSSi is not there anymore (includes Telemetry stuff too). However my Taranis Plus is talking to the Dr4-II fine. I tried re-binding it but still nothing. Any ideas or setting in taranis that I may be missing. My next move is to flash Tx2.0.earlier one.


  8. mark

    Is it possible to just solder on the green wire directly to the telemetry pad on the naze32 with out the header pins? I dont want to have to pull out the naze32 completely.

  9. florian

    Hi Oscar, great and informative work.
    I have also a taranis with a frsky d8r-xp receiver on a cc3d board and since I am new to PPM I am struggling to make it work with no success. I jumped pins 3&4 that would get me ppm signal on pin1, how do I connect the RX pin 1 info to the cc3d? only on the signal pins 1,2,8 ? then how do I power the receiver(before when running it on PWM) the three pins powered also the RX… then how in the world can I get the RSSI level display on my Taranis ? this is the reason I bought the xp receiver in the first place ? :( My Taranis is the European version and I use it with an external RF module, what should I choose in the taranis menu: PPM mode ?
    The radio binds with the xp rx (dim green led on) but I cannot get any reading in the cc3d interface..

    Your support would be appreciated.

    Thanks and greetings from Romania :)

    1. Oscar Post author

      Hi Florian
      i don’t use CC3D, but from a quick google search, i think pin 1 and 2 on CC3D are the 5V power, and pin 8 is the PPM signal input. Your RX is powered by pin 1 and 2.
      When your D8R-XP is in CPPM mode, your Channel 1 is RSSI, you can connect that to your RSSI input on MinimOSD for example.
      Without an OSD, the only way to get RSSI is passing it through one of your spare PPM channel.
      You don’t need to change anything on the Taranis to use PPM, it’s all done on the RX.


  10. Guy

    Hi Oscar,

    Is it possible to use the Analog Telemetry Port to activate a lost plane buzzer alarm? For example, if I turn the Taranis of and RSSI is zero, can it activate the buzzer? Or on falisafe (when again the TX is off)?


    1. Oscar Post author

      in Cleanflight when you enable Failsafe feature, the buzzer will beep when it detects no RX signal, I think that’s what you are asking?

      1. Guy

        Hi Oscar,

        Thanks for the reply, however, I’m using the D4R with the CPPM so I can’t attach the buzzer to any of the other channels (CH2 is the RSSI and 3&4 are connected with a jumper..), this why I asked about the Analog Telemetry Port..


  11. Ronald

    Thanks for the tutorial.

    I have exactly the same setup, but opentx 2.1.1 has others screens.
    Telemetry is completly different then the screens you display.

    I didnt succeed to setup battery voltage.
    Can you place new screens to setup telemetry?

  12. Bootflag

    Hi Oscar,
    just in addition to Daniel Cruz and for others who may have problems setting up telemetry.
    This is buy far the best video which explains how its done when using a BEC.

  13. Danny Cruz

    Hi Oscar,

    I’m not so sure the Taranis (Open TX) setup part is completely accurate. I see you based it off that YouTube video you link to. However, I read it a bunch of times and I watched the video a bunch of times and what I gather is that the voltage is measured from the BEC if you use A1. I don’t think that’s accurate enough and it certainly doesn’t work for me.

    See, for this to work, we’re assuming the BEC’s voltage will change based on the input voltage from the battery pack. However, who’s to say all BEC’s will change in the same fashion. To give you an example, I use a voltage regulator. The one I use is super precise and efficient. It always feeds my Naze32 with 4.95V no matter what the flight pack’s voltage is. I want to also assume some BEC’s will be this precise as well. This would make this method not work because you will always get the same exact reading for your voltage.

    I still kept A1 active, simply to monitor my voltage regulator in case it ever fails. However, to actually get a proper voltage reading, there is more to it. For that, I changed the voltage source to “Cells” in Open TX. Then I edited the “Voltage Scale” in Cleanflight, from 110 up. So far, I’ve found 112 gives me the most accurate reading, but I’m still adjusting and I’m off by a few decimals. The other thing I did was select FrSky Auto telemetry in “Ports” on Cleanflight and I inverted the telemetry signal (since apparently it’s inverted for FrSky) in the CLI using “set telemetry_inversion = 1”.

    This seems to work well so far. By the way, the video I used to learn this is this one: – There are various parts to this video.

      1. Daniel Cruz

        Thanks. Glad I can help. I’ve kept learning more and there are even more ways to do this. I think the inversion thing is only really needed when using the soft-serial port instead of the telemetry port… but that might also be because my FC already has inversion capabilities built in. Some FCs don’t.

  14. Azlan


    I have taranis x9d plus with D4RII . Problem is i cannot get the lipo cell and cells reading from the Taranis since using opto esc and powering the naze32 through UBeC. Already checked wirings ,soldered pin and FC and previously when using BS esc without the UBEC , i can get the lipo reading from Taranis.

    Please reply ASAP because i have searched everywhere for the solution. Thanks

  15. Tony

    I am having issues getting this working. I have a Naze32 Full and D4R-II. I want to use the softserial so I can also run a MinimOSD.

    I go into the Ports tab on cleanflight, enable SOFTSERIAL1, check MSP and select Telemetry as FrSky. I connect the greenwire from my D4R-II to PIN 6 on the 10 pin group. I get nothing.

    Any suggestions?


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