Inexpensive Raspberry Pi based tablet as projected whiteboard or for screen casting

By Jonathan Gutow (version 1.2, December 9, 2020)

For less than US$400 you can build a quite capable tablet that works well as a projected whiteboard and is capable of producing nice screen casts of what you write. Additionally, it has capabilities that many more expensive tablets do not:

1. It has a real operating system with full access to FOSS software.
2. The tablet pen is pressure and tilt sensitive with the right software (GIMP, Xournal++), so can be used as a real artists drawing/painting display.
3. With the addition of a USB keyboard, mouse and an inexpensive wire stand to prop up the display, it can serve as a decent home computer that is reasonably portable.
4. If you add a USB power bank you have a portable artists drawing display/tablet.
   

* Recommended (equivalent of what I am using).

Recipe

The easiest way to do this is buy a simple plastic case for the Pi. This will leave you with a minimum of three cables to deal with: power supply, cable to artists display, cable to projector system. If you want a more elegant tablet and portable tablet see my notes on building a case and powering it with a USB power bank.

OS

Rasbian (easiest install)

1. You will need access to another computer or have purchased a kit that includes a microSD card with NOOBS pre-installed.
   
2. For the install you also need a USB mouse, USB keyboard and a monitor (artist display will work). Once set up you can use without the mouse and keyboard.
   
3. If you did not buy a kit with NOOBS installed follow the instructions for NOOBS install at RaspberryPi.org.
   
4. If you have a microSD card with NOOBS installed, you basically have to put the SD card in, plug in the cables and boot it up. It is still probably worth seeing the instructions.

1. You will need access to another computer to do this. I have successfully done this using *nix OSes (Linux and MacOS), your mileage may vary if you try other OSes.
2. Follow this Ubuntu Tutorial to get the server image installed on your SD card. I currently recommend 20.04LTS 64 bit.
3. You then need to check some things in the hardware settings before installing the Lubuntu desktop:
1. Bluetooth is disabled by default (as the Pi bluetooth is flakey in my experience that is fine). If you really want it enabled you need to modify files as instructed in the directory microSDcard:/boot/firmware/nobtcfg.txt.
2. Set hdmi parameters so that you can plug and unplug some monitors. Edit the usercfg.txt (microSDcard:/boot/firmware/usercfg.txt to contain the following lines.

#Overscan messes up most modern LCD/LED displays. Disable it.
disable_overscan=1


#It would be nice if monitors powered down when the Pi 4 sleeps the screen, but it is not implemented yet.
# However, this command will make it work once it is implemented.
hdmi_blanking=1


#Enable both hdmi outputs even if a screen is not plugged in. This will run your Pi a bit hotter and use more power.
hdmi_force_hotplug:0=1
hdmi_group:0=2#Only the Pi 4 has two hdmi ports
hdmi_force_hotplug:1=1
hdmi_group:1=2
#The following may need to be adjusted depending on the projectors available see the video settings at raspberrypi.org.
# This is appropriate for a maximum resolution of 1680X1050 on the second monitor.
hdmi_mode:1=57

#GPU settings
dtoverlay=vc4-fkms-v3d


3. Put the microSD card into the Pi. Hook up mouse, keyboard and monitor (artists display) to hdmi port 0.
4. Boot up the Pi and create your user administrator account.
5. Connect to hardware ethernet. This is a big install. You do not want any dropping out in the middle.
   
6. Install the desktop.
   

sudo apt update
sudo apt install lubuntu-desktop

7. When the install is complete you can reboot: sudo reboot now
8. On reboot you should get a graphical login.
   

Software

1. Install "whiteboard" software. Xournal++ recommended (many features including pressure sensitivity).
1. You will need to get this from a special repository (ppa).

   sudo add-apt-repository ppa:apandada1/xournalpp-stable
sudo apt update
sudo apt install xournalpp

2. Install a screen overlay/annotator. If you are going to want to write over images, slides, etc. displayed on your screen you will get better performance using a screen overlay/annotator than putting images in the background of your "whiteboard" The downside is that your notes will not be recorded if you are not recording your screen. On the command line type "sudo apt install gromit-mpx"
   
3. Install screen recording software. On the command line type "sudo apt install vokoscreen".
4. If you are using this as a projected whiteboard you need to set the screens to mirror mode in the Display settings.
1. Make sure the screen dimensions are correct for the projector you are using. Things will not look good if the projector has to rescale the image.
2. The default is to mirror with the upper left corners of the screens aligned. If the projector screen is lower resolution than your artists display (recommended artist displays are 1920 X 1080) the right hand side and some of the bottom of the screen will not be projected.
   
5. Some thoughts on using the software:

• Whiteboard (Xournal++): I set up a template with 6 blank pages in it for a one hour lecture. The template should also be set up so that it sized appropriately to show up on the projected screen. I then open the template and save a copy named for the date and class. When screen casting, I only record part of the screen, leaving space for the recording software controls. If I have slides to show I usually convert them to .png files and load them into the template before class as images. Then I can write on them, move, enlarge or shrink them during class.
• Vokoscreen: This requires some fiddling. Exactly which input will give you audio depends on your specific microphone system. You also need to play with the microphone placement to avoid breathing noises and other unwanted noise.
  

Notes on building a portable version (under construction).