Flashing Frsky Receiver using Flight Controller Pass-Through

So you want to flash Frsky RX firmware, but too lazy to take your quad apart? You can flash it through your flight controller, just like how you flash your BLHeli ESC’s using FC pass-through.

Important: “FC Pass-Through” requires SmartPort connected and working correctly in the first place.

Further Reading: Frsky Receiver Options for Mini Quad

Advantages of Flashing Frsky RX via Pass Through

You can flash Frsky receivers using your Taranis, but there are some advantages to using FC pass through:

  • No need to remove your RX from the quad
  • No fiddling with connectors
  • Not everyone has a Taranis TX for flashing TX

The Steps

Download FRSKY Tool or “Tool-FrSky update sport” from here: https://www.frsky-rc.com/frusb-3-fuc-3/

Download receiver firmware from: http://www.frsky-rc.com/download/?sort=Firmware&cate_id=12&pro_id=0; Note the file you will flash. EU version has “LBT” in the filename, international version has “FCC” in the filename

  1. Plug in the your flight controller via USB, and connect to Betaflight Configurator. Go to the Ports tab and note the port you are using for SmartPort.
  2. Go to CLI, type serialpassthrough [UART-1] 57600 (for example, if you are using UART 3 for SmartPort, “UART-1” is 2, and you should type serialpassthrough 2 57600)
  3. Disconnect from Betaflight Configurator
  4. Power off your quad, disconnect USB and LiPo battery, make sure RX is not powered
  5. Open up FRSKY tool (make sure you right click the icon, and run as administrator). Select the RX firmware file
  6. Connect USB, and plug in the LiPo to power on your FC and RX
  7. If the FRSKY tool detects the receiver successfully, it should now display the current firmware version and hardware version number
  8. You can now download and flash, it will take about 2 minutes

You will need to bind your TX and RX again after flashing receiver firmware.

Not Working? Some Troubleshooting

It is very important that the receiver is turned off before opening the Frsky Tool.

You should power your FC and RX with a LiPo battery, otherwise the RX might drop out during flashing due to insufficient power.

7 thoughts on “Flashing Frsky Receiver using Flight Controller Pass-Through

  1. wade tubman

    does this technique work on softserial (for s.port i need soft serial). I try “serialpassthrough 10 57600” fpr softserial 1 but it does not recognise it

    Reply
    1. Rastislav Stana

      From the betaflight serial documentation: the port number is 30 so you need to do: serialpassthrough 30 57600

      Reply
  2. Jorge Jimenez

    I have been having the same issue where I cannot select COM4 until the FC is powered on. And this FC powers the receiver, so the bootloader window passed. I watched JB’s video and basically the fix is to at least temporarily move the receiver V input to a pad that does not provide power when the FC is connected to USB. Here’s that video youtu.be/Hzf-EuQZYsE

    Reply
  3. Jamie

    In order to get this to work on BF 3.4 and old X4R-SB, I had to manually change my MSP port to 57600 also (vs default 115,200).

    Also to be clear do *not* include ‘UART’ in the command line (I did this a few times before realizing my mistake).

    Reply
  4. Jamie

    Very timely article (needing to do this myself) however an inherent problem: when the quad is disconnected the COM port is not yet enumerated in Windows, and so the FySky tool will not let you select the COM port (and will not allow you to change it after selecting the file). Maybe I’m missing something?

    Reply

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