[shiura] had a problem — they wanted a nice high-quality audio output for their computer, but they didn’t fancy any of the DACs that were readily available on the market. They specifically wanted one that was affordable, capable, and included a graphic equalizer so they could simply hook it up to a regular amplifier and dial in the perfect sound. When they couldn’t find such a device, they decided to build their own.

The build is based around a Raspberry Pi Pico, chosen for its feature set that makes it easy to configure as a USB audio device. It’s paired with a Waveshare Pico Audio module, which is based on the PCM5101A stereo DAC and slots neatly on top of the microcontroller board. An SPI-controlled LCD screen was also fitted in order to display the graphic equalizer interface that [shiura] whipped up. The project write-up explains the code required to implement the equalizer in detail. A four-channel equalizer was possible on the original Pi Pico (RP2040), while upgrading to a more powerful Pi Pico 2 (RP2350) allowed implementing eight channels in total.

If you’re looking to build a digital audio system with the ability to do some equalization to suit your listening room, this might be a project of interest to you. We’ve featured other projects in this realm before, too.

Apple was all-in on WiFi from the beginning, launching the AirPort line of products to much fanfare in 1999. In 2004, along came the AirPort Express—a fully-functional router the size of a laptop charger, that offered audio streaming to boot. As [schvabek] found out that while a lot of older Apple gear has long ago been deprecated, the AirPort Express is still very much supported and functional to this day!

Generally, you wouldn’t expect to plug in a 20-year-old Apple accessory and have it work with the company’s modern hardware. However, upon slotting the AirPort Express into a wall socket and starting the initialization process, [schvabek] noted that it was detected perfectly well by his post-2020 Macs. Only, there was a small problem—the configuration process would always stall out before completion.

Thankfully, there was a simple remedy. [schvabek] found that he could connect to the AirPort Express with his classic white plastic MacBook and complete the process. From there, he was astonished that Apple’s servers let him pull down a firmware update for a device from 2004. After that upgrade, the AirPort Express was fully functional with all his modern Apple gear. He could readily stream audio from his iPhone and MacBooks with no compatibility issues whatsoever.

It’s nice to see Apple still supporting this ancient hardware to this day. It’s a nice contrast when companies like Sonos are more than happy to brick thousands of old devices just for the sake of progress.

Just about every “getting started with microcontrollers” kit, Arduino or otherwise, includes an ultrasonic distance sensor module. Given the power of microcontrollers these days, it was only a matter of time before someone asked: “Could I do better without the module?” Well, [Martin Pittermann] asked, and his answer, at least with the Pi Pico, is a resounding “Yes”. A micro and a couple of transducers can offer a better view of the world.

The project isn’t really about removing the extra circuitry on the SR-HC0, since there really isn’t that much to start. [Martin] wanted to know just how far he could push ultrasound scanning technology using RADAR signal processing techniques. Instead of bat-like chirps, [Martin] is using something called Frequency-Modulated Continuous Wave, which comes from RADAR and is exactly what it sounds like. The transmitter emits a continuous carrier wave with a varying frequency modulation, and the received wave is compared to see when it must have been sent. That gives you the time of flight, and the usual math gives you a distance.

Since he’s inspired by RADAR, it’s no surprise perhaps that [Martin]’s project reminds us of SDR, and the write-up gets right into the signal-processing code. Does it work better than a chirping module? Well, aside from using fewer parts, [Martin] can generate a full range plot for all objects in the arc of the sensor’s emissions out to 4 meters using just the Pico. [Martin] points out that it wouldn’t take much amplification to get a greater range. He’s not finished yet, though — the real goal here is to measure wind speed, which means he’s going to have to go full Doppler. We look forward to it.

This isn’t the first time we’ve seen the Pico doing fun stuff at these frequencies, and Doppler RADAR is a thing hackers do, so why not ultrasound?