Embedded Computing Design

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.

As you probably know, Raspberry Pi single-board computers, especially Pi 4 models, can get quite hot. While passive cooling options are often good enough to avoid overheating and thermal throttling, at some point you’ll need to think about using a cooling fan. The Raspberry Pi’s GPIO pins don’t supply enough current to power even a small fan, but there are several ways to power and control a fan with the Pi.

The vast majority of computer control is done by hand, using a keyboard, mouse, or touchscreen, but what about your feet? They’re perfectly capable of tapping out a signal, but generally sit unused when at a computer. In my latest experiment, I set out to see if common spring-loaded foot pedals would work as a computer interface, perhaps for controlling shift, control, or other modifier keys. Short answer: yes, it can work. There are, however, a few complications.

As a PCB design becomes more involved, managing complexity becomes ever more important to the process. Last month’s article about using hierarchical sheets presents an excellent tool for organizing schematics. This is helpful, but at the end of the day these theoretical connections must be transferred to the PCB layout editor for on-screen routing, and ultimately physical manufacturing. To help simplify physical routing, consider how components will be arranged when designing your schematic.

For simple KiCad circuit designs, a sheet with lines going from one component to another is good enough. Add in net labels, and slightly more complicated drawings can be cleaned up nicely. At some point, however, your design may become too large to fit onto a standard sheet. You’re faced with a choice: expand the sheet to cover more area–useful, but often clumsy–or break schematic data up into a series of linked hierarchical sheets.

Some time ago, I wrote an article about panelization basics, mostly focusing on “mouse bites” as the panel separation technique. The other way to separate boards is using a technique called v-scoring. The basics of this technique are shown in the Royal Circuit Solutions video below, which is meant to selectively weaken a PCB for separation at a later point.