They look like this:

Image of low-level functions

By default, when you refer to a vix file, it looks like this:

<Reference Type="VILib" Name="TerminalTerminal.vix" />

But, to refer to these low-level functions, you need to write:

<Reference Name="X3.Lib:StartBlockTest" Type="VILib" SubType="StartBlock"/>

Where can I find this "X3.Lib"?

Thanks in advance, Csabi

1 Answer 1


The LEGO EV3 Block Developer Kit documentation refers to these as "gray blobs". These are compiler intrinsics and don't have a .vix implementation. They generally correspond directly to the bytecodes from the EV3 Firmware Developer Kit.

Note: Developer kits are available on the official LEGO MINDSTORMS download page.

  • Thank you so much! This is exactly what i was looking for! I didn't except to get an answer so quickly, since most of the questions here are about Lego minifigures, but it's nice to know there are also people like you, that know a lot about the EV3 brick
    – MoCsabi
    Aug 31, 2021 at 14:26
  • The main reason I asked this question, is because the Start block seemingly has a "result" output. Do you have any idea what thats for?
    – MoCsabi
    Aug 31, 2021 at 14:27
  • I think the start block is a little different that other blocks since it starts a VM thread instead of calling a specific bytecode command. The output is probably just the program flow wire that connects to the next block to run. Aug 31, 2021 at 19:12

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