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#68 Can't download programs via USB tower

John Hansen
BricxCC (17)
Joe McKenzie

OS: Windows XP SP 3
Computer: Sony Vaio UX (UMPC, has USB and no serial ports)
BricxCC version: (6/29/09 4:14:14 PM), installed following directions for RCX on BrixCC main page
RCX: tried with both hardware 1.0 and 2.0, both with official Lego firmware 2.0
Tried settings BrixCC to "RCX" and "RCX2"

Whenever I try to download a program to the RCX using my Mindstorms 2.0 USB tower, I get the error "serial port could not be opened and/or configured". I can successfully connect to the RCX, download firmware, run programs that are already on the RCX, control motors, etc. Tools-->Diagnostics sees no problems.

I tracked this problem to the command line BricxCC is using to start NQC. It is running
nqc.exe -E"C:\DOCUME~1\joemck\LOCALS~1\Temp\temp.log" -L"C:\DOCUME~1\joemck\LOCALS~1\Temp\temp.lst" -I"C:\Program Files\BricxCC" -TRCX2 -d "C:\DOCUME~1\joemck\LOCALS~1\Temp\temp.nqc"
(WITHOUT specifying the port the tower is on! Of course, NQC can't find the tower and exits with exit code -1.)

I successfully downloaded the same program to my RCX by manually issuing this command:
nqc.exe -Susb -E"C:\DOCUME~1\joemck\LOCALS~1\Temp\temp.log" -L"C:\DOCUME~1\joemck\LOCALS~1\Temp\temp.lst" -I"C:\Program Files\BricxCC" -TRCX2 -d "C:\DOCUME~1\joemck\LOCALS~1\Temp\temp.nqc"
(Just added the -Susb specifier.)


  • Found a workaround: In Preferences->Compiler->NBC/NXC, uncheck the "use internal compiler" box. If it's checked, the "-S" switch is not generated for NQC.

  • Joe McKenzie
    Joe McKenzie

    Oops, sorry, that "nobody" workaround comment was me.

  • John Hansen
    John Hansen

    • status: open --> closed-fixed