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COM Port already in use error meesage

Created Wed, 28 Dec 2011 21:55:57 +0000 by redarmy1


Wed, 28 Dec 2011 21:55:57 +0000


Sorry if this topic is already within the forums, I have recently purchased a Max 32 board however I am a complete novice with regards to microcontrollers.

I have downloaded the mpide software which was linked within the Max32 board on the websited and have installed the FDMI port on to the computer.

When I try the basic blink program within the arduino software the error message COM port is already in use close any programs using this port. However I cant see any other program which is using the port. As when I remove the MAX 32 board from the computer com4 (which is what im using) disappears.

I have set the jumpers to the Master position and have tried pressing the manual reset however nothing seems to get it going.

If there are any ideas as to why this is happening any suggestions would be great as im really keen to get my design off and running


Wed, 28 Dec 2011 22:06:16 +0000

I'm not really sure what may be going on here.

The first thing that I would suggest is to make sure that you are using the latest version of the MPIDE software. A new release was put out on 12/21. The URL below should point you at the latest version. This version is substantially better than the previous release.

It may be a driver installation problem. Do you have any more information to describe the symtoms/behavior?

Gene Apperson Digilent


Thu, 29 Dec 2011 09:03:32 +0000


I have installed the newest software and tried to update the device with the latest driver in the mpide folder the computer stated that the newest driver has already been installed. The full error message I get when I try to upload the blink programme to the board has been attached.

Ill look into the driver installation this afternoon however when I look under the COMport its stated as an FTDI device which id have thought would mean its been installed ok.



Thu, 29 Dec 2011 10:22:02 +0000

I get this ( port in use ) if i forget to remove the serial connection I am using from pins 1 and 0 (tx rx ) the download stays orange no errors , except if i try again. I guess this is because the usb / serial shares these pins .I have to disconnect usb to PC , remove the serial connection and reconnect usb . do you have something on pins 0 and 1.


Thu, 29 Dec 2011 13:07:39 +0000


No I have nothing on the pins, I cant even view the serial monitor as the same message occurs have removed and reinstaled the software however still getting the same result on the two different computers I am trying it on


Thu, 29 Dec 2011 14:09:14 +0000

Tricky one... Without the chipkit plugged in how many ports are available in MPIDE ?

the Pins refered to were UNO not Max don't know if they are the same.


Thu, 29 Dec 2011 15:49:38 +0000


The board only has a mini usb supply, both the usb serial converter and the port are stating they are fdmi, if the board itself was faulty would this be an expected error message at all?


Thu, 29 Dec 2011 16:11:15 +0000

sorry I meant If you look at the ports available in MPIDE without the Max usb plugged in.... then plug in max usb..... MPIDE should report the new port ?


Thu, 29 Dec 2011 16:15:07 +0000

Yes sorry a new port is detected which corresponds to the ftdi port i set up


Thu, 29 Dec 2011 16:35:37 +0000

OK serial on this board ever worked ? any leds flashing during upload ? upload button staying orange ?


Thu, 29 Dec 2011 16:42:01 +0000

I have only ever had this message, the other leds work and the upload led flashes to signal that some data is getting sent however thats all i have


Thu, 29 Dec 2011 16:52:09 +0000

As I commented if i leave a connection to serial pin, the upload fails and stops orange I have to unplug usb to get over error.

UNO has two leds that flash during upload ?


Thu, 29 Dec 2011 17:24:23 +0000

Yes max 2 does aswell. However i only get ld1 flashing at present when uploading i have tried unplugging the usb however it also doesnt work when i check the com port there are 3ftdi files stated on the driver details and also one microsoft file would this affect it. Ive read that other java files can affect uploading


Thu, 29 Dec 2011 21:22:12 +0000

I imagine one led is TX the other is RX flagged by the FTDI so I suspect you are sending but not getting an ACK back (just a guess) usually some time out would occur , the 'Port in use' error is down to the file not sent yet , this is why if I tie TX of my UNO to another output at 0v the same thing happens. not much help to you , suspect some problem on the Max serial port. have you e-mailed Digilent support ?


Thu, 29 Dec 2011 22:40:55 +0000

That will be my next step was just seeing wether anybody else had experienced such problems thanks for your help


Fri, 30 Dec 2011 09:15:30 +0000

Just a final thought , does the reset switch check out , I once had one that was stuck on closed although it still clicked... regards.

Jacob Christ

Fri, 30 Dec 2011 19:06:39 +0000

Can you open the port with a different term program?



Fri, 30 Dec 2011 19:37:47 +0000


The reset button is fine and the port itself works fine the problem only occurs when using mpide.


Mon, 02 Jan 2012 17:28:36 +0000

Hey I am having a similar problem although I can connect to the board and upload sketches. I can also open the serial monitor. The problem I am having is when I try to connect to the board using Python it gives me a "COM8 port access denied error". I have also tried installing the VCOM and D2xx drivers but windows will not allow it since it is happy with the ones installed.

I cant post a link to the thread on here but it just a few threads up: "Max32 Python Problems"

not much help to but at least we can commiserate! I'll keep an eye on this thread to see if you come up with anything. Nobody cares about MY problems apparently. :) no one has replied!


Tue, 03 Jan 2012 12:07:01 +0000

This won't be much help , not used python however the FTDI usb chip on the chipkit boards 'remember' what port they are I have 2 Uno's they always come up with their own port number (3 and 4 ) , the fact u loaded and ran a sketch , would point to other software probs. (Access denied could be protecting the bootloader ?)