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Author Topic: Multiple Arduinos = multiple comm ports?  (Read 878 times)
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I purchased 3 knock-off Duemillenove Arduinos, and tried each of them out. Each time I connected the Ardunio to my laptop, a new comm port was assigned (but only the first time I installed that physical board). The comm port number seems to follow the board - when I plug in the first board, it uses the comm port which it originally assigned to that board. It looks like there may be some kind of serial number in the FTDI chip?

Is there any way to cause the computer to assign the same comm port to all of the Arduino's I plug in?

Thanks,

    Steven
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yes every board has its own serial id, what is the problem with the boards  having a different com port from one another? and assigning a specific ID is not something you can just "edit"
« Last Edit: October 05, 2011, 10:25:57 pm by eddiea6987 » Logged

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On linux (and possibly macs) it's always /dev/ttyUSB0

At least, it is for me.
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... what is the problem with the boards  having a different com port from one another?

It just is wasteful. Also, if I am switching between a bunch of Arduino boards I don't want to have to keep selecting a different comm port in the IDE.

-- Steven
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It just is wasteful.

Wasteful?  Interesting use of the word.

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Is there any way to cause the computer to assign the same comm port to all of the Arduino's I plug in?

http://www.google.com/search?q=windows+change+serial+port+assignment
http://www.sealevel.com/support/article/AA-00441/154/Resource-Center/Serial-Interfaces/How-to-change-asynchronous-serial-COM-port-assignments-in-Windows-Device-Manager.html
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It just is wasteful.

Wasteful?  Interesting use of the word.


I have quite a few devices which show up as comm ports, and certain software (like terminal emulators) have an upper limit as to the comm port number (the famous "who would ever need more than 16 comm ports??" thinking). I have had to in the past uninstall various device drivers to "free up" comm port numbers.


Thanks for this information. My question wasn't too clear - I wanted the 3 Arduino's to use the same device driver instance. You aren't supposed to have different instances of device drivers point to the same comm port (I've had problems in the past doing this). Windows gets picky on this.

Someone mentioned the unique serial numbers of each FTDI chip which causes different instances - it looks like I am stuck, as that doesn't appear to be anything I can affect.

Thanks for the suggestions!

-- Steven
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Someone mentioned the unique serial numbers of each FTDI chip which causes different instances - it looks like I am stuck, as that doesn't appear to be anything I can affect.
If you read the FTDI's data sheet on its Internal EEPROM (section 4.2), you'll see you can (re-)program its serial number.

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf
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If you read the FTDI's data sheet on its Internal EEPROM (section 4.2), you'll see you can (re-)program its serial number.

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

Thank you James! That is exactly what I was looking for.
I programmed all 3 devices with the same serial number, and they all now show up as the same comm port!

Ain't the internet wonderful...

-- Steven
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If you read the FTDI's data sheet on its Internal EEPROM (section 4.2), you'll see you can (re-)program its serial number.

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

Thank you James! That is exactly what I was looking for.
I programmed all 3 devices with the same serial number, and they all now show up as the same comm port!

Ain't the internet wonderful...

-- Steven


Reading through the utility program that FTDI makes available, I saw this:

Quote
It is also possible to fix the serial number to a fixed 8-digit alphanumeric string; however we do not recommend this as systems will only recognize the first instance of such a device connected to a PC.

I read that to mean that if you convert all your FTDI based arduino boards to have the same serial number, you will give up the chance to be able to have more then one attached to your PC at any given time. So a trade-off of sorts?

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... you will give up the chance to be able to have more then one attached to your PC at any given time. So a trade-off of sorts?

Yes, that is what I understood and I accept that limitation. I have no plans of having multiple Arduino's connected to my computer (if I do, I can re-change the serial numbers...)

-- Steven
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