I'm new here. I used to use the old Mindstorms to teach robotics at a school back in early 2000s and I thought my grandson would like it, so I have bought an old second hand system. The RCX brick works and the tower is connected to the USB-serial port adapter. It says the RCX is working fine and will download 4 or 5 prog blocks. If I try more it tries but won’t download. Do you have any ideas?

  • I've encountered this issue before, but I'm not sure if I remember how I solved it. What OS are you using (and what usb-to-serial converter, if you have that info as well?) In the meantime try the suggestions here: bricks.stackexchange.com/questions/10160/…
    – MindS1
    Commented Feb 15, 2022 at 20:54
  • Thanks will look up info.
    – Jotec
    Commented Feb 16, 2022 at 9:02
  • Thanks it is running on XP sp3. I have looked at your link but so far no progress. Additionally when I exit the software something remains as it will not reload saying only one copy of mindstorms can run.
    – Jotec
    Commented Feb 16, 2022 at 10:15
  • Now failing to download built in progs!
    – Jotec
    Commented Feb 16, 2022 at 10:17
  • 1
    Glad to hear it! My understanding is this is a fairly common issue, so I've summarized our discussion in the answers section so future people can benefit.
    – MindS1
    Commented Feb 21, 2022 at 16:02

1 Answer 1


Summarizing our discussion from the comments:

System is running Windows XP SP3 (not a VM) with an (unknown) USB to Serial converter connected to the Serial IR Tower.

Problem is that most interactions with the RCX are unsuccessful; Communication begins, but is typically interrupted partway through downloading programs to the brick.

  1. OP attempted suggestions from this post, with no luck.
  2. Tried a different RCX with no luck.
  3. Tried a different WinXP system with a built-in serial port and downloads were successful. Indicates the problem is with the USB to Serial converter.

Conclusion: Not all USB to Serial converters are compatible with the Mindstorms Serial Tower. It is known that USB to Serial converters based on the PL2303 chipset work reliably, but this information is not always readily available. PL2303 has driver support for Windows 98 thru Windows 10, currently available for download here.

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