The Pi Pico, An SDR Receiver Front End

June 5, 2024 by Jenny List 22 Comments

Making a software defined radio (SDR) receiver is a relatively straightforward process, given the right radio front end electronics and analogue-to-digital converters. Two separate data streams are generated using clocks at a 90 degree phase shift, and these are passed to the software signal processing for demodulation. But what happens if you lack a pair of radio front ends and a suitable clock generator? Along comes [Mordae] with an SDR using only the hardware on a Raspberry Pi Pico. The result is a fascinating piece of lateral thinking, extracting something from the hardware that it was never designed to do.

The onboard RP2040 ADC is of course far too slow for the task, so instead an input is used, with a negative feedback arrangement from another GPIO to form a crude 1-bit ADC. A PIO peripheral is then used to perform the quadrature mixing, resulting in the requisite pair of data streams. At this point these are sent over USB to GNU Radio for demodulating, mainly for convenience rather than necessarily because the microcontroller lacks the power.

The result is a working SDR front end, demonstrated pulling in an FM broadcast station. The Pico has to be overclocked to reach that frequency and it’s more than a little noisy, but we’re extremely impressed with how much has been done with so little. Oddly it isn’t the first Pico SDR we’ve seen, but the previous one was a much more conventional and lower-frequency affair for the European Long Wave band.

Schematic of the Pi Pico wireup, showing the various outputs that the firmware will generate on the GPIOs

A Scope Test Tool You Can Build With Just A Pico

May 31, 2024 by Arya Voronova 24 Comments

Ever wanted to see how well your oscilloscope adheres to its stated capabilities? What if you buy a new scope and need a quick way to test it lest one of its channels its broken, like [Paul Wasserman] had happen to him? Now you only need a Pi Pico and a few extra components to make a scope test board with a large variety of signals it can output, thanks to [Paul]’s Sig Gen Pi Pico firmware.

Despite the name it’s not a signal generator as we know it, as it’s not flexible in the signals it generates. Instead, it creates a dozen signals at more or less the same time — from square waves of various frequencies and duty cycles, to a PWM-driven DAC driving eight different waveforms, to Manchester-encoded data I2C/SPI/UART transfers for all your protocol decoder testing.

Everything is open source under the BSD 3-Clause license, and there’s even two PDFs with documentation and a user manual, not to mention the waveform screenshots for your own reference.

It’s seriously impressive how many features [Paul] has fit into a single firmware. Thanks to his work, whenever you have some test equipment in need of being tested, just grab your Pico and a few passive components.

Running Four Brushless Motors With A Single Pi Pico

May 17, 2024 by Zoe Skyforest 15 Comments

Sometimes, you have to drive four motors, and you need to do so with a certain level of control. You could throw a lot of parts at the problem, but you don’t necessarily have to. As [Shaun Crampton] demonstrates, you can run four brushless DC motors with a single Pi Pico.

[Shaun] set about developing a brushless motor controller from scratch with the Pico, relying on its PIO hardware and the TI DRV8313 — a handy three phase motor driver. Before he knew it, he was implementing field oriented control (FOC) in MicroPython, only to find that it was a little too slow for proper motor control work. He soon switched to C for the lower overheads, and was readily driving a brushless motor with his own code. Before long, he’d implemented torque limiting and PID speed control. He was even able to optimize things to the point where he had four motors hanging off a single Pi Pico, complete with Hall sensors for feedback.

The full story is well worth reading, as it goes from “Hello, World” all the way to the end of the project. If you’ve never experienced the joy of your own code getting a motor to spin, you might enjoy following in [Shaun’s] footsteps. Files are on GitHub for the curious.

We’ve seen a lot of motor controllers around here, many of which draw heavily from other projects online. It’s a great way to learn the basics of what is a very well established field. Meanwhile, if you’re cooking up your own project in this space, do drop us a line!

BreadboardOS, A Command Line Interface For The Pico

May 14, 2024 by Zoe Skyforest 25 Comments

Operating systems! They’re everywhere these days, from your smart TV to your smartphone. And even in your microcontrollers! Enter BreadboardOS for the Raspberry Pi Pico.

BreadboardOS is built on top of FreeRTOS. It’s aim is to enable quick prototyping with the Pi Pico. Don’t confuse operating system with a graphical environment — BreadboardOS is command-line based. You’d typically interface with it via a serial terminal emulator, but joy of joys, it does support color!

Using BreadboardOS is a little different than typical microcontroller development. Creating an application involves adding a “service” which is basically a task in FreeRTOS parlance. The OS handles running your service for you. Via the text interface, you can query running services, and start or kill them at will.

Meanwhile, running df will happily give you stats on the flash usage of the Pi Pico, and free will tell you how full the memory is doing. If you really want to get raw, you can make calls to control GPIO pins, the SPI hardware, or other peripherals, and do it right on the command line.

BreadboardOS isn’t for everyone, but it could prove a useful tool if you like that way of doing things. It’s not the only OS out there for the Pi Pico, either!

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This Tiny Game Boy Lets The Real Thing Play Online

May 13, 2024 by Tom Nardi 5 Comments

Back in 2021, [stacksmashing] found that it took little more than a Raspberry Pi Pico and some level-shifters to create a USB connection with the Game Boy’s link port. Add in the proper software, and suddenly you’ve got online multiplayer for the classic handheld. The hardware was cheap, the software open source, and a good time was had by all.

Inspired by both the original project and some of the hardware variations that have popped up over the years, [weiman] recently set out to create a new version of the USB link adapter that fits inside a miniature 3D printed Game Boy.

The big change from the original design is that this is using the far smaller, but equally capable, RP2040-Zero development board. This is mated with a SparkFun logic level converter board (or a clone of one from AliExpress) by way of a custom PCB that also includes the necessary edge connectors to connect directly to a Game Boy Link Cable.

Once the PCB is assembled, it’s dropped into the 3D printed Game Boy shell. [weiman] really worked some nice details into the case, such as aligning the d-pad and buttons in such a way that pressing them engages either the RESET or BOOTSEL buttons on RP2040-Zero. The screen of the printed handheld also lines up with the RGB LED on the top of the dev board, which can produce some cool lighting effects.

The original project from [stacksmashing] was an excellent example of the capabilities of the Pi Pico, and we’re glad to see it’s still being worked on and remixed by others. Even though the state of Game Boy emulation is nearly perfect these days, there’s still something to be said for working with the original hardware like this.

Pi Pico Gets A ZX Spectrum Emulator

April 27, 2024 by Zoe Skyforest 9 Comments

The Pi Pico is a capable microcontroller that can do all kinds of fun and/or useful things. In the former vein, [antirez] has ported a ZX Spectrum emulator to the Pi Pico.

ZX2040, as it is known, is a port of [Andre Weissflog’s] existing ZX spectrum emulator. It’s designed for use on the compact embedded Pi Pico platform, using ST77xx TFT displays. To that end, it has a UI optimized for small, low resolution screens and minimal buttons. After all, very few Pi Picos come with a full QWERTY keyboard attached.

Certain hacks are necessary to make it all work; the chip is overclocked to get things humming fast enough. The emulator also runs upscaling or downscaling in realtime as needed. This allows the emulator to run with a variety of displays, almost none of which are a direct match for the ZX Spectrum’s original resolution of 256×192 pixels.

Code is on Github for the curious, including a great run down from [antirez] on everything that makes it tick. If you want to play ZX Spectrum games on a keychain, you’d do well to start here. There are other projects to emulate it on the Pico, too! Video after the break.

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Building A Giant Boardgame Isn’t Easy

April 19, 2024 by Zoe Skyforest 8 Comments

[Stevenson Streeper] is a maker, and was recently charged with a serious mission. He had to prototype, design, and build a board game. A software-controlled board game, that is, and one that was 400 square-feet in size. As you might imagine, this ended up being a tall order, and he’s been kind enough to share his tale on his blog.

His client’s idea was for a giant interactive game board akin to the glowing disco floors of old. It had to play a game approximating the rules of “The Floor Is Lava.” It had to handle up to 20 players at a time, too.

[Stevenson] runs a company that delivers “Activations”—basically big showpieces for customers willing to pay. This wasn’t his first attempt at building an immersive attraction, but it was a big job, and a challenging one at that. He explains the difficulties that came about from a limited crew, limited timeline, and a number of difficult missteps. Hurdles included surprise unusable off-the-shelf hardware and the difficulty of hand-sanding 144 tiles of polycarbonate. One weeps for the project’s plight early on – if only the AliExpress tiles were documented.

He may have bitten off more than he could chew, and yet—the project was finished and to a decent degree of functionality success. That’s to be applauded, and [Stevenson] learned a ton along the way. Big projects can be daunting and can put you in a bind. As this story demonstrates, though, perseverance often gets you somewhere okay in the end. Video after the break.

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