"Terminate the existing connection" for Raspberry Pi webcam despite not existing

Hi,

I'm trying to connect a Raspberry Pi and its HQ camera with MATLAB, through the Hardware Support Package. The installation was successful and I was able to contact the board and generate an r object with raspi().

r = 

  raspi with properties:

         DeviceAddress: '192.168.1.45'                
                  Port: 18734                         
             BoardName: 'Raspberry Pi 4 Model B'      
         AvailableLEDs: {'ACT'}                       
  AvailableDigitalPins: [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27]
  AvailableSPIChannels: {}                            
     AvailableI2CBuses: {'i2c-0','i2c-1'}             
      AvailableWebcams: {'unicam (platform:fe801000.csi)'}
           I2CBusSpeed: 100000                        
AvailableCANInterfaces: {}    

As you can see, a webcam is detected right off the bat. When I try to access the webcam with a variable

    w = webcam(r)

I get the following error message.

unicam (platform:fe801000.csi) is in use. You need to terminate the existing connection first

by clearing the webcam object.

I suspect it's because the availableWebcams field but I can't terminate the connection because my workspace is free of variables and I can't delete the contents of the field because it's read only. There is absolutely no information online about this situation and I would like to ask for some guidance.

Thanks.

Answer 1

[sudobash]

Hi Javi,

There may be several reasons for why this may happen:

• It may be possible that another persistent variable is holding onto the webcam resource. Type the following commands to clear all the variables and the current webcam variable:

clear all
clear w

• There may be multiple instances of MATLAB running and one of the other instances has an active connection to the webcam. Close all running instances of MATLAB and try again.
• There is also the possibility that another program running on the Raspberry Pi is using the webcam. Run the following command on the Raspberry Pi's terminal and kill any process that may show up:

lsof /dev/video0

Hope this helps!