What is the relationship between a Lego RCX 1.0 brick and these:

Robotics Invention System (RIS) versions

  • 1.0
  • 1.5
  • 2.0

RCX firmware:

  • firm0309.lgo: RCX firmware version 3.09
  • firm0328.lgo: RCX firmware version 3.28
  • firm0332.lgo: RCX firmware version 3.32

2 Answers 2


The main differences between the versions were:

  1. Firmware - although later versions of the firmware were backwards compatible with the earlier bricks
  2. Power Adaptors:
    1. RIS/RCX 1.0 had a power socket on the brick as well as battery options
    2. RIS/RCX 1.5 removed the power socket from the brick
    3. RIS/RCX 2.0 Functionally equivalent to RCX 1.5
  3. IR Tower connections:
    1. RIS 1.0 and 1.5 had a serial connection for the IR Tower
    2. RIS 2.0 had a USB connection for the IR Tower, which doesn't operate nicely with 64bit Operating Systems (ironically* the serial connection does work with a serial-USB adaptor apparently)
  4. Manuals - I believe the Constructopedia was more comprehensive in 1.0 than in 2.0.

* I say ironically as I originally returned my 1.0 or 1.5 set as I was unable to get the serial connection to work on my PC at the time and later bought a 2.0 which worked fine then, but not any more on my more modern hardware.


There is no significant hardware difference (*) affecting software between the RCX bricks, so 1.0 brick is compatible with all firmware and RIS versions.

(*) Known hardware differences:

  • RCX 1.0 sold with RIS 1.0 had a power adapter plug.
  • RCX 1.0 sold with RIS 1.5 no longer had this plug.
  • RCX 2.0 had a 76 kHz IR interface instead of 38 kHz. It remains compatible with old versions (harmonic 2) albeit with a slightly reduced range. New frequency allows to communicate with Spybots bricks.
  • 1
    Doesn't the earlier RCX 1.0 brick have a power adapter plug, which has been eliminated in the RCX 1.0 brick supplied with RIS 1.5 and in the RCX 2.0 brick supplied in RIS 2.0?
    – Phil B.
    Sep 15, 2016 at 10:51
  • Yes it does, but doesn't matter for software. Answer edited for more details!
    – Philo
    Sep 16, 2016 at 8:06

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