Raspberry Pi Pico

128 Articles

USB DAC Comes With Graphic EQ

November 28, 2025 by 5 Comments

[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.

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A 3D-printed assembly standing on short legs is visible. A portion extends upward with the word "Nord" sunk into it. Cables extend from one side of the upright portion, and a side view of a circuit board is visible at the front of the assembly.

Measuring Earth’s Rotation With Two Gyroscopes

November 23, 2025 by 42 Comments

We’ve probably all had a few conversations with people who hold eccentric scientific ideas, and most of the time they yield nothing more than frustration and perhaps a headache. In [Bertrand Selva]’s case, however, a conversation with a flat-earth believer yielded a device that uses a pair of gyroscopes to detect earth’s rotation, demonstrating that rotation exists without the bulkiness of a Foucalt pendulum.

[Bertrand] built his apparatus around a pair of BMI160 MEMS gyroscopes, which have a least significant bit for angular velocity corresponding to 0.0038 degrees per second, while the earth rotates at 0.00416 degrees per second. To extract such a small signal from all the noise in the measurements, the device makes measurements with the sensors in four different positions to detect and eliminate the bias of the sensors and the influence of the gravitational field. Before running a test, [Bertrand] oriented the sensors toward true north, then had a stepper motor cycle the sensors through the four positions, while a Raspberry Pi Pico records 128 measurements at each position. It might run the cycle as many as 200 times, with error tending to decrease as the number of cycles increases.

A Kalman filter processes the raw data and extracts the signal, which came within two percent of the true rotational velocity. [Bertrand] found that the accuracy was strongly dependent on how well the system was aligned to true north. Indeed, the alignment effect was so strong that he could use it as a compass.

In the end, the system didn’t convince [Bertrand]’s neighbor, but it’s an impressive demonstration nonetheless. This system is a bit simpler, but it’s also possible to measure the earth’s rotation using a PlayStation. For higher precision, check out how the standards organizations manage these measurements.

The Simplest Ultrasound Sensor Module, Minus The Module

November 16, 2025 by 5 Comments

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.

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Bit-banged 100 MBit/s Ethernet Transmission On Raspberry Pi Pico

October 18, 2025 by 25 Comments

The Raspberry Pi Pico is a very capable board, but it’s still a surprise to see bit-banged 100 MBit/s Fast Ethernet implemented on one. [Steve]’s Pico-100BASE-TX library allows an RP2040 (or RP2350) microcontroller to stream data at roughly 11 Mbyte/s, enough to implement 100 MBit/s Fast Ethernet transmission.

We’ve seen 10BASE-T implemented on a Pico, but it takes a lot more than just shoveling bits faster to get 100BASE-T working. 10BASE-T uses two voltage levels and Manchester encoding, but 100BASE-T uses three voltage levels, which [Steve] cleverly implemented on the Pico with two GPIOs, and far more complex encoding. Check out the repository’s README for details as well as a couple example applications.

[Steve] tells us that to the best of his knowledge, this is the first bit-banged 100 MBit/s Ethernet implementation using a microcontroller. It’s transmit-only — reception being an entirely different beast — but it’s possible some enterprising soul might find a solution. If you do, be sure to let us know all about it!

2025 One Hertz Challenge: Drop The Beat (But Only At 60 BPM)

July 28, 2025 by 1 Comment

Mankind has been using water to mark the passage of time for thousands of years. From dripping stone pots in Ancient Egypt to the more mechanically-complicated Greco-Roman Clepsydrae, the history of timekeeping is a wet one — and it makes sense. As an incompressible fluid, water flows in very predictable patterns. If you fill a leaky pot with water and it takes an hour to drain, it will also take an hour the next time you try. One Hertz Challenge entrant [johnowhitaker] took this idea in a different direction, however, with an electromechanical clock that uses dripping water as an indicator.

This clock uses a solenoid to briefly pop the plunger out of a water-filled syringe. This allows a drop to fall from the tip, into a waiting beaker. In addition to the satisfying audio indication this produces, [johnowhitaker] added a bit of food coloring to the dripping water for visual flair. The entire thing is controlled by a Raspberry Pi Pico and a motor driver board, so if you’ve got some spare parts lying about and would like to build your own be sure to head over to the project page and grab the source code.

While this clock isn’t exactly here for a long time (either the syringe will eventually empty or the beaker will overflow), it’s certainly here for a good time. [John] and commenters on his project even have ideas for the next steps: a 1/60 Hz beaker changer, and a 1/600 Hz spill cleaner. Even so, the first couple of drops hitting the beaker produce a lovely lava lamp-esque cloud that is a joy to watch and has us thinking about other microfluidics projects we’ve seen.

And remember — it’s not too late to enter the 2025 One Hertz Challenge!

Sand Drawing Table Inspired By Sisyphus

June 30, 2025 by 7 Comments

In Greek mythology, Sisyphus was a figure who was doomed to roll a boulder for eternity as a punishment from the gods. Inspired by this, [Aidan], [Jorge], and [Henry] decided to build a sand-drawing table that endlessly traces out beautiful patterns (or at least, for as long as power is applied). You can watch it go in the video below.

The project was undertaken as part of the trio’s work for the ECE4760 class at Cornell. A Raspberry Pi Pico runs the show, using TMC2209 drivers to command a pair of NEMA17 stepper motors to drag a magnet around beneath the sand. The build is based around a polar coordinate system, with one stepper motor rotating an arm under the table, and another panning the magnet back and forth along its length. This setup is well-suited to the round sand pit on top of the table, made with a laser-cut wooden ring affixed to a thick base plate.

The trio does a great job explaining the hardware and software decisions made, as well as showing off how everything works in great detail. If you desire to build a sand table of your own, you would do well to start here. Or, you could explore some of the many other sand table projects we’ve featured over the years.

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Meet Cucumber, The Robot Dog

June 27, 2025 by 6 Comments

Robots can look like all sorts of things, but they’re often more fun if you make them look like some kind of charming animal. That’s precisely what [Ananya], [Laurence] and [Shao] did when they built Cucumber the Robot Dog for their final project in the ECE 4760 class.

Cucumber is controllable over WiFi, which was simple enough to implement by virtue of the fact that it’s based around the Raspberry Pi Pico W. With its custom 3D-printed dog-like body, it’s able to move around on its four wheels driven by DC gear motors, and it can flex its limbs thanks to servos in its various joints. It’s able to follow someone with some autonomy thanks to its ultrasonic sensors, while it can also be driven around manually if so desired. To give it more animal qualities, it can also be posed, or commanded to bark, howl, or growl, with commands issued remotely via a web interface.

The level of sophistication is largely on the level of the robot dogs that were so popular in the early 2000s. One suspects it could be pretty decent at playing soccer, too, with the right hands behind the controls. Video after the break.

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