Why Use XM+ Plus Receiver for Taranis?

The XM+ radio receiver is a tiny SBUS diversity RX from Frsky. It’s insanely light weight making it a great alternative to X4R-SB and XSR RX for micro quad builds. In this post we will show you the features of XM+ and how to use it.

Get your Frsky XM+ receiver from http://bit.ly/2nx0pe6

For more information about RX, check out our list of Frsky radio receivers for mini quads.

What are the advantages of XM+ receiver?

  • Much smaller size and lighter weight than X4R-SB and XSR
  • It’s a full range receiver, similar range to X4R-SB and XSR
  • Using same antenna/connector as the X4R-SB, replacement is very easy
  • It’s possible to direct solder RX to FC with header pins without wires (if FC supports it)
  • Only 3 pins: Vcc, GND and Signal – there is no confusion
  • XM+ is even smaller than the LR1000 by FuriousFPV, great RX option for their micro quads (such as the Moskito70)

Only downside of XM+ RX is the lack of S.Port full telemetry (Smart Port), there is only RSSI telemetry. RSSI has a dedicated solder pad and it’s also available on the 16th channel.

XM+ Frsky RX Radio receiver PCB top XM+ Frsky RX Radio receiver PCB back

Frsky SBUS receiver size comparison - XM XM+ XSR X4R-SB

Credit: http://imgur.com/Jo56aKV

More info on XM+ RSSI Output

For those who would like to display RSSI in OSD.

RSSI pin outputs PWM signal (0-3.3V). Please be aware that this signal should not be connected to MinimOSD directly, as it will give you 0% or 100% only. You will need a digital to analogue converter (low pass filter) to convert PWM to analogue voltage level.

However the XM+ can output RSSI through Channel 16, so in Betaflight/Cleanflight should be set to use CH16 for telemetry signal and limit aux channels to 12.

Binding and Failsafe

Binding and Failsafe Setup process is exactly the same as other X series Frsky Receivers:

Red LED on RX means it’s not bound or not detecting TX. To bind, enter Bind mode on TX, hold down F/S button on RX and power on. After a few seconds, Green LED will light up indicates binding has completed.

To setup up failsafe, power on both TX and RX. Set your TX channels to desire positions, and press the F/S button on the RX. The green LED should flashes and indicates F/S has been setup. Please confirm if F/S is now working as expected by turning off TX. To remove F/S, simply rebind the RX.

Differences Between XM and XM+ (plus) versions

Both are SBUS receivers, but there is some differences between the 2 RX.

  1. Size and Weight are different
    • XM – 15.0×10.0x3.5mm – 1.0g
    • XM+ (plus) – 21.5x12x3.5mm – 1.6g
  2. The XM+ has Diversity Antennas (2 antennas), XM only has 1 antenna. Diversity antennas gives better range
  3. Slightly different input voltage:
    • XM – 3.5V-10V
    • XM+ (plus) – 3.7V-10V

RX is bound, but not getting signal in FC

One common problem getting SBUS to work: RX is bound to TX (solid LED on RX) but not getting signal to FC (no activity in receiver tab).

  • Make sure TX is in D16 mode
  • Some FC has built-in SBUS inversion, some don’t. Try setting SBUS inversion on or off, it normally fix it.
  • set sbus_inversion = on

28 thoughts on “Why Use XM+ Plus Receiver for Taranis?

  1. Ami

    Hi my has that issue it binding fine both no switch inputs are showing active on the quad or in betaflight. Tried switching inversion in cli no diffrence also is in D16 on tx. Please shed some light.
    Regards
    Ami

    Reply
  2. Crysipe

    Hello,

    I do not understand if it is necessary to have DAC or not in order to have RSSI with XM+. It seems that channel 16 of betaflight can handle the input signal as it comes directly from the rssi pad of the xm+, I m confused.

    “You will need a digital to analogue converter (low pass filter) to convert PWM to analogue voltage level.

    However the XM+ can output RSSI through Channel 16, so in Betaflight/Cleanflight should be set to use CH16 for telemetry signal and limit aux channels to 12.”

    Reply
  3. Pete

    Hi Oscar,

    Just wanted to say I really appreciate all your reviews you’ve done since the beginning! They’ve all been really informative. I do have a question related to caps.

    To install caps on mini-drone is it just cap negative to negative (esc or pdb) and cap positive to positive (esc or pdb)? Maybe it’s just a silly question

    Thanks,
    Pete

    Reply
  4. JS

    Hi Oscar, I recently ran into this problem when setting up a new AIO FC with blheli 32 esc on betaflight 3.2. I set it up as usual with my frsky XM+ using sbus but it wouldn’t arm the quad and I notice upon powering up the FC the LED indicator would flash non stop which normally indicates if there is no signal from the rx. But as soon as the FC is usb connected into Betaflight GUI the led flash stop and i could see in the GUI rx tab that all the channels would work normally. I disconnected from GUI and power cycle the quad and again the same thing happened. I did what you said doing the sbus inversion on/off in CLI but still it wouldn’t work. I replaced another new XM+ with the same disappointing results. I did all the firmware updates on the XM+ but still it does not work and all this time the XM+ was bound to my taranis with a solid green light. Than with the last try, I had an old Frsky XSR rx and i plugged it into the FC and tried, immediately it worked like magic. Power up the quad with the usual motor sounding and the FC led blinking afew flashes and stop indicating is ready to arm. And it did arm, this quad built was like any other quad that i have built ready to be flown. This is the 1st time i have encountered that a FC would only take a XSR but not XM+. Any thoughts on this?

    Reply
    1. Silaxe

      Hi JS,
      I unfortunately have the exact same problem.
      I have updated the firmware on the XM+ with XM+LBT170313-RSSI8.frk as my XJT module is in LBT mode.
      The 2 are bound fine (solid green light) but I have no signal in base flight. The FC is an afromini rev 3.
      Just like you it does work fine with an XSR.
      Did you manage to solve the problem?
      Thanks.

      Reply
  5. Frank

    Hi,

    i accidently tried to flash the wrong firmware.
    Now i it is just impossible to flash any firmware on my xm+. Allways get failure message.
    Any advice on this?

    Reply
  6. Chris Young

    Oscar, when using RSSI on ch 16, is it necessary to do any calibration? It would seem that any PWM value 2000 reads 100%. Everything else is in between but there must be a need to calibrate this?

    Reply
    1. Oscar Post author

      no the RSSI on ch16 is a PWM signal not an analog signal, so your FC is probably not seeing the signal correctly.
      You might need a ADC to convert the signal to anaolog signal first before feeding it to your FC.
      Or you can do this hack

      Reply
  7. Adam K.

    Oscar, I have done a lot of range testing with my x4r-sb and these XM+ antennas, and I’m happy to say that I actually get much better range with the XM+! I thought it was a fluke, but after putting 5 xm+ receivers on my quads they all perform the same. I have a test field that I fly, and 1,500 feet out my x4r-sb is getting in the low 70s for RSSI, while the XM+ is still in the mid/low 90s. I don’t really understand how these are getting a good amount better range, but it’s great. Just thought I would share with you and others that read this website!

    Reply
    1. Paul

      I’ve flashed 2 xmplus with latest firmware both 16 and 8 channel for non LGBT.
      And I am getting the worst signal ever.
      Only about 10meters and the quad drops from the sky.

      I’ve tried my x4r and that completely works a treat no drop outs.

      So confirmed it is not the radio.

      Could someone help shed some light on this please?

      Thank you.

      Reply
  8. Alex

    I get a green light after binding but wont arm. was working before on old receiver. Fc is kombini and using a passado osd. do you have any thought on what to check?

    Reply
    1. Oscar Post author

      this is one of those common problem, try to Google it first. But here are a few things you can check:
      – check receiver tab activity
      – check if you have the correct configuration setup for RX

      Reply
  9. fl0PPsy

    Being able to adjust PIDs, Rates and VTX settings over the S.Port link makes not having that feature a big fail for these receivers.

    Reply
    1. Oscar Post author

      like I said in the title, it’s great for micro builds, where space and weight are constraints. Anyway it’s great too on bigger builds if S.Port is not needed.

      Reply

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