Home > Electronics > DIY Interface cable to HeliCommand

DIY Interface cable to HeliCommand

Being somewhat lousy rc-helicopter pilot, I decided to invest to HeliCommand 3a stabilization unit. Unit itself is easy to install but it quickly became clear that pc-interface is almost necessary to operate the unit properly.
I did not want to order the cable separately since the cable is somewhat expensive and can be constructed for few euros. I hacked this circuit together by using some schematic I found from the web and the pictures about the cable pcb as a reference. Interface can easily be constructed on stripboard from easily available components.

The numbers on the leads are numbers for 9-pin D-female connector. Connector to HeliCommand is standard 3-pin female servo plug, where middle connector is not used. When connecting cable to HeliCommand, white wire goes towards the center of the unit. Note that on the pcb image two red squares mark the spots, where the copper strip needs to be cut. Remember to cut traces also under the resistors.

I glued the pcb inside some plastic box which I had laying around and it seems to work fine with the HeliCommand software.

Categories: Electronics Tags: , ,
  1. David
    15/03/2012 at 13:12

    Interesting read: I’ve followed the circuit above but its failed to function 😦

    • 15/03/2012 at 13:20

      Are you using real serial port, or usb to serial adapter? If latter, could you try using different brand adapter. I had at least one adapter I had troubles with. Other than that I don’t have any good tips. Check the connections and the pcb once again.

  2. Raptor
    30/09/2012 at 16:58

    Will be making one of this,will keep you posted. Thank for sharing!

  3. Anonymous
    13/10/2012 at 10:48

    same here does not work

  4. 14/10/2012 at 18:17

    I checked the schematic again. Apologies for those that tried to build this, there’s a mistake in the schematic. The GND(5) wire should go to base (middle) pin of Q2. I’ll update the schematic shortly!

  5. Anonymous
    14/10/2012 at 19:52


    You rock man!, thanks for your time in putting this online, did the change you posted and now im on business, programmed my HC 3d just now.

    Thank s again!


  6. Anonymous
    14/11/2013 at 18:26

    Cut under R1, R3, R4 and R6?
    A real schematic would be better.

    • 14/11/2013 at 18:37

      Yes, those should be cut, otherwise the resistors won’t do much good. Also note the two other cut points (red rectangles with red dot). I could indeed do a schematic when I find time.

  7. Anonymous
    12/06/2015 at 15:52

    would you know which pins to connect on a FTDI adaptor, tried pin to pim mappping but could not connect

    • 12/06/2015 at 16:31

      It won’t work directly with FTDI, since it’s designed to work with real serial port, which has RS-232 signal levels instead if +5v of FTDI. Either you’d need to change the device, or more easily, buy usb->serial cable.

      • Anonymous
        12/06/2015 at 17:51

        Thanks for the explanation.

  8. Anonymous
    27/10/2015 at 22:57

    Tried this using my trusted FTDI adapter and it works! after buying many usb to serial adaptors and using the helicommand original serial cable nothing worked for me so hope this helps anyother person.

    Scroll down to the circuit schematic.


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