I was using VS2015 (C#) to write simple programs for my EV3 using a bluetooth connection. This was working fine for several days and then suddenly stopped. I can't for the life of me figure out why. It's not my code, I don't think, because the sample program that came with the API also won't connect. However, I can connect with LEGO LabVIEW just fine.

What I've tried:

  • Flashed the brick and updated firmware to 1.09H
  • Reinstalled BT devices and drivers on host PC
  • Reboots of brick and PC

I'm not receiving any exceptions on instantiating the brick, ConnectAsync(), nor any DirectCommand calls. Connections with USB do work fine.

Any ideas?

EDIT: I had typed firmware v1.06H (I believed this is what it was). It's currently 1.09H, although I did manually update to 1.07H to no effect.

  • My son's new EV3 with 1.09H doesn't connect the official Android Programmer app, even though Android can see/pair the device. :( (They're not called Brick for nothing?)
    – T-Gergely
    Commented Dec 31, 2019 at 11:53

1 Answer 1


You should always be using the latest firmware. If you have an EV3 brick that was produced in mid 2015 or later, it may have a newer Bluetooth chip that requires firmware v1.07 or higher. See https://bricks.stackexchange.com/a/7237/3498 for an unofficial firmware changelog.

If updating the firmware does not fix the problem then the name of the comm port probably changed. This is something like "COM1" or "COM5". Look in the Device Manager to see what comm port is assigned to your EV3 and make sure it matches your C# code.

  • Thanks for the answer, but unfortunately upgrading the firmware had no effect (see my edit). Also, in case this helps anyone, if you attempt to connect to the wrong COM port an exception will be thrown.
    – David
    Commented May 19, 2016 at 23:19

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