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#14 Unable to upload to Cortex using Windows 8.1


I have been trying to use PROS for my own VEX uses, but cannot upload code to the Cortex. My computer running Windows 8.1 recognizes the Cortex, and programs such as ROBOTC can successfully upload to it. However, PROS cannot. The firmware has been updated, and I have tried running PROS in compatibility mode as well as reinstalling it several times. Also, running as administrator does not help.

The Cortex itself is not the issue, as code can be uploaded to it (tested with a friend's computer running PROS).

When run from the command line, the issue looks like this:
UniFlash v0.7 by Stephen Carlson
Error: No matching ports found for this board (VexFlash); currently connected:
* COM8 (Hardware Serial)

Please advise as to how I can resolve the issue, and if any more information is needed.


  • sli908

    sli908 - 2014-05-01

    A workaround was found where forcing an upload by passing uniflash.jar the -PCOM8 flag forcibly uploaded to Serial Port COM8. However, a true fix where the Cortex is automatically detected has not been found yet.

  • sli908

    sli908 - 2014-05-01

    Doing the workaround once caused it to work perfectly without the workaround afterwards.

  • Stephen Carlson

    Stephen Carlson - 2014-05-13

    Sorry for being slow to update this issue, but it looks like the PROS uploader cannot get traction on the USB identification information in Windows 8.1 for some reason to distinguish the VEX cortex or VEX joystick from other serial ports. Unfortunately, we failed to reproduce the issue on four different Windows 8.1 systems. If this issue recurs, we are willing to investigate further.

  • Stephen Carlson

    Stephen Carlson - 2014-05-13
    • status: open --> closed

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