I wanted to create an electronics bench computer that could be set up to control logic analyzers, GPIO, software-defined radios, and other equipment for running tests and diagnostics on my various projects. Decided to use the Raspberry Pi 4, because it is small and compact, has various IO capability, can be paired with a touch screen, and there is a plethora of software available.
Hardware
You can pick up a Raspberry Pi 4 at Sparkfun along with a bunch of other peripherals that are necessary for setting up the Pi. When I started this project the 8GB Ram version of the Pi 4 was not out yet so I went with the version that had the most amount of ram. This was the 4GB version at the time. This should be powerful enough to run the bench display as well as software applications like the Digilent Waveforms and small GNU Radio flowgraphs.
The Pi 4 is capable of outputting HDMI to a high resolution monitor, but I wanted to be able to move the device around my bench as needed, so I went with a 7in touch screen panel that was developed specifically for the Pi and connects via a ribbon cable.
The Pi 4 is also notorious for its USB-C power connector that does not implement the USB-PD (Power delivery) specification correctly. Therefore getting the right (dumb) cable to power your Pi can be difficult. So I decided to just go with the Raspberry Pi Power supply that is designed to work with the Pi 4.
Raspberry Pi USB-C Power Supply
The last thing to sort out was the enclosure for the Pi 4 and the screen. I could have purchased the SmartiPi Touch 2 that neatly integrates the Pi with the 7in screen, but I decided to 3D print the enclosure, allowing me to save some money on the design.
I also added a small cooling fan small that I had on hand, but I would suggest finding one that fits the enclosure better.
Assembly
Now that the 3D printed pieces have been printed, thanks to my Prusa Mini, we can assemble everything.
Here are a few pictures of the assembly process. It should not be too difficult to follow, the only tricky part is that you need to add the shroud that goes around the Pi before you attach the legs onto the screen.
Software
Now that everything is assembled we can install the OS. Since I am planning to use this with my SDRs there is a variant on the Rasbian OS that comes pre-installed with software such as GNURadio and other SDR software, which can be a pain to install from scratch, called pisdr-image. This image was created and is maintained by Luigi F. Cruz who is always asking the community about new software that should be added to the image.
The image installs the same way as pretty much every raspberry pi image but the instructions are listed on the PiSDR web page along with the download links. Once everything is installed we can plug in an RTL-SDR and open GNURadio with a simple frequency sink to see if everything is working. This is possibly the fastest I have ever been able to get to a frequency plot in GNURadio!
The other piece of software that I wanted to install was Digilent Waveforms for Analog Discovery. This software, along with the Analog Discovery device, turns the pi into a mixed-signal oscilloscope, waveform generator, and protocol decoder. The link to the software provides raspberry pi specific installation instructions.
I have the older version of the Analog Discovery that I purchased when I was an undergrad student at an amazing discount! They usually run about $300 which is still a fantastic deal for all that they do.
To complete the setup I enabled VNC access, using a RealVNC free account, so I can log into the pi from anywhere if need be. I also purchased this Bluetooth keyboard and mouse combo but it is only good for simple tasks while I am at the bench.
Conclusion
I am not sure what I am going to use this device for yet but it should be fun to play around with. There are a few more problems I need to solve, one is the screen resolution where some windows are too large to be displayed. The second is that the touch accuracy is off so I need a way to calibrate it.
I am imagining this device running one or two main programs once all configured, which will help me quickly test other electronics projects on my bench. To do this am also looking into running Kivy to create custom python GUI’s that can take better advantage of the small touch screen.
Example of Kivy running on the Pi.
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