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UC Davis Center for Integrated Computing and STEM Education (C-STEM) --- Research and Outreach
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Q: I can’t connect Raspberry Pi through VNC viewer with Ethernet connection.

A: It may caused by many reasons. You can follow the checklist below to figure it out step by step.

  1. Flash your micro SD card with the latest C-STEMbian.
  2. Plugin the micro SD card into the Pi before power it.
  3. Install Bonjour on your computer. (Please refer this question if you don’t know how to install)
  4. Please refer the Apple’s article to make sure Bonjour has been successfully installed on your computer.
  5. Make sure Bonjour service is enabled on your computer. If you don’t know how to check it, please refer the question.
  6. Connect the Pi to your computer with an Ethernet cable.
    1. Try different Ethernet cables.
    2. Try different USB to Ethernet converters if you are using one.
  7. If all of them listed above are checked, you can try to reboot your computer and the Raspberry Pi.
  8. Contact us for support through this page.


Q: How to install Bonjour on my computer?

A: Windows users can download and install Bonjour Print Services v2.0.2. Bonjour should be installed on Mac by default.


Q: How to make sure Bonjour service is enabled on my computer? If not, how can I start it?


  1. Press the Windows key + “R” to open the “Run” dialog. Type “compmgmt.msc” without quotes in the Run dialog box, and press “OK” to open the Computer Management window.
  2. Click the arrow next to “Services and Applications” in the left pane to expand it, and then select “Services.”
  3. Click the “Name” column header in the middle pane to sort the services alphabetically. Right-click “Bonjour Service” and choose “Start.” Wait approximately five seconds for the service to start.
  4. Right-click “Bonjour Service” again, and select “Properties.” On the General tab, choose “Automatic (Delayed Start)” from the drop-down list next to “Startup type” and click “OK.” Close the Computer Management window.

Q: I cannot launch Linkbot Labs from C-STEM Studio in Raspberry Pi.
A: In the current version of Linkbot Labs for Raspberry Pi, you will need to connect to the internet in order to launch Linkbot Labs.


Q: In C-STEM Studio, when I click “Web-Based Computing,” it displays that “This site can’t be reached, refused to connect.” How can I fix this?
A: By default, the Apache web server in C-STEMbian is not started. You can start, stop, reload and restart it by the commands below.

  • start it with: sudo /etc/init.d/apache2 start
  • stop it: sudo /etc/init.d/apache2 stop
  • reload the config with: sudo /etc/init.d/apache2 reload
  • restart (stop followed by start): sudo /etc/init.d/apache2 restart


Q: If I do not use Linkbot lab, how can I disable the service for Linkbot lab to save CPU time?
A: baromeshd is an auto-start service during start-up.  You can use the command ‘sudo systemctl stop baromeshd.service’ to temporary stop it and the command ‘sudo systemctl disable baromeshd.service’ to permanently stop it from auto starting.


Q: Linkbot Labs is open but it says I am in Offline Mode even though I am connected to the internet.
A: You may need to restart the baromeshd service. You can use the command ‘sudo service baromeshd start’


Q: When I run a program in ChIDE I get the error message “Unable to open I2C device: No such file or directory”
A: You need to enable automatic loading of the I2C kernel module by following the below steps

  1. Open the Applications Menu
  2. Click “Preferences”
  3. Click “Raspberry Pi Configuration”
  4. Click “Interfaces”
  5. Enable I2C


Q: My screen is too big or flickering.
A: You may need to adjust the resolution.

  1. Open the Applications Menu (in top right corner of screen)
  2. Click “Preferences”
  3. Click “Raspberry Pi Configuration”
  4. Click “Set Resolution…”
  5. Choose an appropriate resolution for your monitor. (for example: CEA mode 16 1920×1080 60Hz 16:9)
  6. It will ask you to reboot. Click Yes. 


Q: The keyboard is not typing properly.
A: You may need to adjust the keyboard settings.

  1. Open the Applications Menu (in top right corner of screen)
  2. Click “Preferences”
  3. Click “Mouse and Keyboard Settings”
  4. Click “Keyboard”
  5. Click “Keyboard Layout”
  6. Click “United States”
  7. Select “English (US)”


Q: The monitor is not responding when I connect my Raspberry Pi.
A: You may need to adjust the settings on your monitor. Using the buttons on the monitor, you can change the input source to connect the monitor to the Raspberry Pi.