In a previous post, we explored how the Digilent Analog Discovery 2 (AD2) and its WaveForms software is a phenomenally versatile “multitool for electrical engineers,” acting as an oscilloscope, function generator, logic analyzer and more. At under $300 and at a size that can fit in the palm of your hand, it’s truly a bargain for those just getting started, or who simply don’t have enough bench space for the multiple tools it can replace.
관련 상품 참조
One of the tradeoffs of the Analog Discovery board, and really any “headless” test system, is that you need to use your own computer as an interface. This is fine in a pinch, but more often than not, your computer is occupied with other tasks, and finding the proper desk setup for it and whatever you’re testing can be cumbersome.
Analog Discovery 2 and Raspberry Pi 4 Setup
However, the Analog Discovery 2 and its WaveForms software work with the Raspberry Pi 4 (and only the Pi 4 as of this writing). This means it’s possible to build a dedicated system with these two elements that’s semi-portable and doesn’t occupy your main computing platform. Follow along to see how to make one yourself. It’s a fantastic project that could be extremely helpful for those that need to work from home at times.
What You’ll need
· Raspberry Pi 4 (2GB RAM version tested)
· Micro SD card (32GB tested, other sizes may work)
· Raspberry Pi mounting hardware and/or heat sink, described later
· Power strip with 3A USB C connector
· VELCRO adhesive
· 3/16” acrylic, or other similar surface
· (4) M4-.07 x 12mm screws for VESA monitor mounting
· BNC probes and/or BNC minigrabbers
· Flat Panel Monitor (19” used here via DVI to HDMI adapter)
· Micro HDMI to HDMI adapter and cable as appropriate for your monitor
Digilent Waveforms Raspberry Pi Installation
IMAGE 1: Good, but not yet great
First, install Raspbian onto an SD card for your Pi. I used balenaEtcher, but NOOBS should also work if you’d rather go that route. The desktop version without recommended software was used here in order to keep things clean—note that Raspbian Lite without a GUI will not work.
With your Pi running on a spare monitor (and possibly using a Bluetooth keyboard and mouse, discussed later in this article), download the ARM version of WaveForms by first selecting ARM as the “Operating System”, then select and download Linux ARM-32bit.deb. Download the Adept 2 runtime, selecting the ARM/Raspberry Pi version.
Install the Adept 2 runtime by double-clicking on the downloaded .deb file; then do the same for WaveForms. Once installed, click on the raspberry icon in the upper-left hand corner of the screen, navigate to Programming, and voila, there’s WaveForms, ready to run. Plug in your Analog Discovery 2 via its Micro USB port, and one of the Pi’s USB 3.0 ports (the blue ones), and open the software to take measurements and output signals.
You now have an extremely versatile piece of test equipment that can operate without tying up your main desktop/laptop. On the other hand, you’ve still got components strewn about your workspace. Let’s see how we can clean things up!
Raspberry Pi 4 Monitor Mount
IMAGE 2
Once you’ve verified that everything works in a loose configuration, it’s time to make it into a true all-in-one setup. On the very low end, this could mean something as simple as loosely attaching the Analog Discovery 2 and Pi to the back of a computer monitor for reasonably easy transport. In my case, I went a few steps further and made a backing plate out of 3/16-in. acrylic. Inside, I cut a 100mm x 100mm VESA hole pattern (actually three, so the position could be adjusted) for M4 x 0.7 screws, allowing it to attach to a wide variety of monitors.
IMAGE 3: The backing plate can be made in acrylic, or other materials as expedient.
I also added a handle in the acrylic to make it a little easier to move. This isn’t strictly necessary but could certainly make things easier as it’s transported from workspace to workspace. Finally, there’s a cutout on the bottom for access to monitor connections. My plate was manufactured on a CNC router, but this could be constructed with a variety of other automated or manual fabrication methods.
IMAGE 4
Exclusive of the handle and bottom cutout, the plate is 16” x 10”. This gives enough room for the Raspberry Pi 4, power supply, AD2, a BNC adapter (for easy and more precise measurement) and even a small Bluetooth keyboard. Each of these elements was attached to the back using VELCRO fasteners, electrically connected as appropriate, and then secured with zip-ties. The power strip used here features a 3.0A USB-C supply built in, as well as two 120VAC outlets. This allows the entire setup to plug in with one cable.
Note that the Pi isn’t attached with VELCRO directly to the backing plate, but instead utilizes the 3D-printed tapped mount. There’s also a zip-tie mounting version available if that’s more convenient. A cooling enclosure, like one of the options discussed in this article, is another option for holding the Pi. This could also provide some protection for the device and keep it from overheating.
Connect Raspberry Pi to Bluetooth Keyboard
For interface, I chose a Bluetooth keyboard/mouse, which is set up on the Pi via the Bluetooth icon in the upper-right hand portion of the Raspbian GUI. To allow it to connect automatically on startup, enter bluetoothctl in the terminal, then when in that interface, input trust <keyboard MAC address>.
Results: Better Than a Dedicated Oscilloscope?
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In terms of pure measurement abilities, the Analog Discovery 2's specs certainly aren’t comparable to many other oscilloscopes and dedicated test equipment that cost much more. This is discussed in more detail in the “traditional” AD2 post linked earlier. What really stands out with this build, however, is its portability, versatility and low cost.
Using a dedicated Pi 4 and monitor setup here is arguably less portable than the Analog Discovery 2 by itself, but greatly enhances its everyday usefulness and versatility. It can be left on, ready to take quick measurements throughout your workday—not after finding a bunch of cables and plugging them in. While you couldn’t stuff it into a suitcase as easily, consider that you can transport it from your office to shop or other remote area without also unplugging your laptop.
Consider also that what you have is not “just” an electronics measurement device and signal generator, but an actual computer. If you need to use other computer-powered equipment, like a USB microscope, you can just plug it into the Pi for display. Using a monitor gives you a huge screen, compared to most scopes, and the display possibilities are virtually limitless. For that matter, you could also operate this device remotely using VNC Connect or other software, opening up an even greater range of exciting options.
So in some ways, this setup does rival dedicated oscilloscopes that cost much more. For roughly $400-$500 and a little work, you can have an extremely versatile, semi-portable electronics tool, with a variety of display options and even remote access capabilities. Perfect for working from home, educational use, or even taking your lab on the road!
