MATLAB: Serial Read Error

serial communication interfaceserial port

I am trying to read data from serial port. The port being used is COM1. I am getting the following error :
??? Error using ==> serial.fopen at 72
Port: COM1 is not available. Available ports: COM8, COM17, COM19.
Use INSTRFIND to determine if other instrument objects are connected to the requested device.
Please suggest possible reasons.
[Merged information from duplicate question]
I am using Windows 7 32 bit. Matlab verison is 2011a.

Best Answer

1) The COM port name you are trying to use perhaps does not correspond to a valid COM port
2) The COM port might already be in use in that MATLAB session. Quit and restart MATLAB and try again.
3) COM1 might already be allocated for the mouse (serial mouse, older systems)
4) COM1 might already be allocated for use as a modem (a problem seen more often on laptops)
5) You are using a virtual COM port over USB and you did not have it connected at the time you started MATLAB
6) You are using a virtual COM port over USB and you disconnected it at least once after you started MATLAB
7) You are using an older system in which COM1 shares the interrupt line with COM5 and COM5 is already in use
8) Installation problems
9) User Access Controls set up on COM1 do not allow you to use it
10) It is MS Windows; it doesn't need any good reason to act oddly.
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