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Author Topic: Different COM port number for every board  (Read 503 times)
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Just getting started on the Arduino platform.  I got things going fine with the tutorial and quickly got my application code written and tested.  I disconnected the first UNO board I was using to develop code on and connected a second identical board (ie also an UNO).  I came to the conclusion that I needed to reinstall the driver and let Windows XP recognize this board as a different COM port number (the first was installed as COM9 the second as COM10).

Is there a more elegant solution available here?  Is there any way to just have any Uno (or in fact any Arduino) recognized as COM9 without reinstalling drivers?

Is this behavior limited to XP?

Any suggestions would be appreciated.

Details:
  Host OS is Windows XP
  Dev Tools Version is Arduino 0022
  All the boards I'm using are Arduino Uno.
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What happens if you keep the COM ports the same and change boards?
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In my experience the COM port seems to go with the FTDI chip - I have 2 duemilanoves, one comes up as COM3, the other as COM10, while my FTDI-basic I use for programming prominis comes up as COM7.

Can't speak to ATMega8U2s on the UNOs.
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Thanks for the replies.  To answer Baum's follow-up - when I unplug an Arduino board the COM port associated with that board is no longer valid.  It will no longer be shown among the choices when you check the pull down menu for ports.

CrossRoads reply backs up my conclusion that the FTDI architecture/driver leads to this (somewhat unfortunate) situation where each board is assigned it's own port number.
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my conclusion that the FTDI architecture/driver leads to this (somewhat unfortunate) situation

This is not unfortunate.  What is unfortunate is that the newer Arduinos don't have any way to distinguish between devices.  Think about what happens when you hook up both devices at the same time...

An UNO uses an ATmega as the USB interface. You are seeing a windows driver issue and not a hardware issue.

-j
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