Embedded Computing Design

When we last left my 3D-printing adventures in late 2021, I had printed a holder for a Ryobi cordless drill, assembly jigs for my macro pad, and piping adapters for laser fume extraction. Since then, I’ve designed and/or printed a wide range of new items, and this article outlines a few of my favorite useful 3D-prints for 2023.

Recently I’ve been considering how to run an LED for a really, really long time on a CR02032 battery, and eventually (re)stumbled upon the idea of a joule thief. The video below does a good job outlining how this circuit works.

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Engineering, by its very nature, is a technical pursuit, involving numbers, the translation of science into practical applications, and a lot of tinkering to get things just right. Pursuits such as sports, art, music, writing, and other such “squishy” subjects are fine, but could be considered secondary in nature.

In this article, I’ll first outline the basics of using MIDI with CircuitPython on the Pico for direct interface with a computer. I’ll then show how a Pi 4 (or 3/2) can be used as a host to pipe signals to a keyboard or other device.

As a consequence of my review of the OWON HDS2102S oscilloscope/signal generator, and the more recent OWON HDS242 article, I have a signal generator and scope temporarily available. What better time to explore filtering options, namely the band-pass filter!

While some microcontrollers use a tiny amount of power in shutdown mode–and even while running in some cases–e.g. the ATtiny series–others are more demanding. This can be especially true for dev boards with their additional overhead, and/or if you’re using sensors that never quite turn off power-wise.

In a recent article, I outlined how to play MP3 files on the Raspberry Pi Pico with no extra components, just a small speaker. I also talked about doing this with the addition of an amplifier. While either is fine for many applications, the Pico does not have a true ADC, meaning it instead uses less-than-perfect PWM to simulate an analog output. For better audio quality and output level control, you can instead use digital I2S signaling.

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The RP2040, with a processing speed of 133 MHz, is capable of decoding MP3 files, and the Pico RP2040 dev board includes 2 MB of Flash–enough to store a significant amount of compressed audio. At a list price of $4, the Pico therefore makes an incredible and cost-effective platform for embedded audio playback.

Recently I happened upon a 3D CAD package¹ called SolveSpace. While not the only free and/or freemium package on the market, something about its dark, simplistic interface seemed intriguing. A quick download and install on my Mac OS machine, and I had it running. It boots up in around a second, and it takes up less than 30MB installed, both big positives in my book.

Placing components in the KiCad 6 PCB editor is fairly easy in a broad sense. If you have your grid set correctly, and enough space, getting things roughly in place and connected is fairly trivial. However, what if you need to place a number of footprints in a line, or need to make a grid of vias? Placing each one individually can be tedious, so for these tasks use the align, distribute, and array commands to save  a massive amount of time and frustration!

Depending on your level of electronics knowledge, work, and/or experimentation, a voltmeter may be sufficient for your diagnostic needs. However, being able to see the way an electronic signal changes over time, or perhaps even multiple signals, takes your analysis capabilities to a whole new level.

This September (2022), Arduino announced that its much anticipated 2.0 IDE has been moved to stable and is available for download. New features include the ability to use the serial monitor and plotter simultaneously, quicker compilation, auto-complete, and a number of other enhancements that make it a huge improvement overall.

The Raspberry Pi RP2040 microcontroller, along with the Pico dev board, and the Pico W (WiFi), have taken the maker world by storm since its original introduction in early 2021. And for good reason, as at $4 for the Pico, $6 for the ‘W, and around a dollar for the chip itself, this 133MHz Arm Cortex-M0+ processor based device is quite an interesting piece of hardware.

Perhaps you remember the early voice synthesizers of the 1980s, which “spoke” in a muffled, marginally intelligible tone. Audio data storage was based on a linear predictive coding (LPC) format, and played back with a voice synthesis processor (VSP).

Printed circuit boards are, at their most basic, a way to arrange conductors that travel between solder-mounted parts. At the same time, they’re extremely strong sections of precision-cut and coated fiberglass, that could have structural uses as well.

If you’re looking for a great way to get started with the ESP32, the Wemos/LOLIN S2 mini is an excellent option. It comes in a form factor compatible with the ESP8266-based Wemos/LOLIN D1 mini, and the S2 mini can thus work with D2 mini shields. Ground, Vbus, and 3V3 pins are in the same place, though the IO pin numbering is different, so any swaps would certainly require a bit of reprogramming for proper functionality.

Today we’re required to use a password for everything from Google, to PlayStation, to Costco, and any number of other websites and services in-between. Using one password for everything is a serious vulnerability, and keeping multiple passwords written down on a notecard, or as a plain text file on your computer are both problematic. Even dedicated online password keepers can be hacked.