Microcontrollers

2242 Articles

PicoCray - Raspberry Pi Pico Cluster

Parallel Computing On The PicoCray RP2040 Cluster

April 9, 2023 by 28 Comments

[ExtremeElectronics] cleverly demonstrates that if one Raspberry Pi Pico is good, then nine must be awesome.  The PicoCray project connects multiple Raspberry Pi Pico microcontroller modules into a parallel architecture leveraging an I2C bus to communicate between nodes.

The same PicoCray code runs on all nodes, but a grounded pin on one of the Pico modules indicates that it is to operate as the controller node.  All of the remaining nodes operate as processor nodes.  Each processor node implements a random back-off technique to request an address from the controller on the shared bus. After waiting a random amount of time, a processor will check if the bus is being used.  If the bus is in use, the processor will go back to waiting.  If the bus is not in use, the processor can request an address from the controller.

Once a processor node has an address, it can be sent tasks from the controller node.  In the example application, these tasks involve computing elements of the Mandelbrot Set. The particular elements to be computed in a given task are allocated by the controller node which then later collects the results from each processor node and aggregates the results for display.

The name for this project is inspired by Seymore Cray. Our Father of the Supercomputer biography tells his story including why the Cray-1 Supercomputer was referred to as “the world’s most expensive loveseat.” For even more Cray-1 inspiration, check out this Raspberry Pi Zero Cluster.

Debouncing For Fun And… Mostly, Just For Fun

April 9, 2023 by 13 Comments

In our minds and our computer screens, we live in an ideal world. Wires don’t have any resistance, capacitors don’t leak, and switches instantly make connections and break them. The truth is, though, in the real world, none of those things are true. If you have a switch connected to a lightbulb, the little glitches when you switch are going to be hard to notice. Hook that same switch up to a processor that is sampling it constantly, and you will have problems. This is the classic bane of designing microcontroller circuits and is called switch bounce. [Dr. Volt] covers seven different ways of dealing with it in a video that you can see below.

While you tend to think of the problem when you are dealing with pushbuttons or other kinds of switches for humans, the truth is the same thing occurs anywhere you have a switch contact, like in a sensor, a mechanical rotary encoder, or even relay contacts. You can deal with the problem in hardware, software, or both.

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Pi Microcontroller Still Runs A Webserver

April 7, 2023 by 14 Comments

At first glance, the Raspberry Pi Pico might seem like a bit of a black sheep when compared to the other offerings from the Raspberry Pi Foundation. While most of the rest of their lineup can run Linux environments with full desktops, the Pico is largely limited to microcontroller duties in exchange for much smaller price tags and footprints. But that doesn’t mean it can’t be coerced into doing some of the things we might want a mainline Pi to do, like run a web server.

The project can run a static web page simply by providing the Pico with the project code available on the GitHub page and the HTML that you’d like the Pico to serve. It can be more than a static web page though, as it is also capable of running Python commands through the web interface as well. The server can pass commands from the web server and back as well, allowing for control of various projects though a browser interface. In theory this could be much simpler than building a physical user interface for a project instead by offloading all of this control onto the web server instead.

The project not only supports the RP2040-based Raspberry Pi Pico but can also be implemented on other WiFi-enabled microcontroller boards like the ESP8266 and ESP32. Having something like this on hand could greatly streamline smaller projects without having to reach for a more powerful (and more expensive) single-board computer like a Pi 3 or 4. We’ve seen some other builds on these boards capable of not only running HTML and CSS renderers, but supporting some image formats as well.

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One of the PCB projects involved being held in the author's hands - a large-ish green board, with two Pi Picos visible on it

RP2040 And 5V Logic – Best Friends? This FX9000P Confirms!

April 5, 2023 by 25 Comments

Over the years, we’ve seen some modern microcontrollers turn out to be 5V-tolerant – now, RP2040 joins the crowd. Half a year ago, when we covered an ISA card based on a Pi Pico, [Eben Upton] left a comment saying that RP2040 is, technically, 5V tolerant for GPIO input purposes. The datasheets don’t state this because the reality of 5V tolerance isn’t the same as for natively 5V-tolerant chips – for instance, it doesn’t extend all the way to 5.5V for it to be ‘legally’ 5V-tolerant, as in, what 5V tolerance typically means when mentioned in a datasheet.

Having read that comment, [Andrew Menadue] has set out to test-drive the RP2040 GPIO capabilities, in a perfectly suited real-world scenario. He’s working with retro tech like Z80-era computers, using RP2040 boards for substituting entire RAM and ROM chips that have died in his FX9000P. Not only do the RP2040-driven replacements work wonders, using RP2040 boards also turns out to be way cheaper than sourcing replacements for chips long out of production!

Previously, [Andrew] used level shifter chips for interfacing the RP2040 with 5V systems, but he’s rebuilt a few designs of his without level shifters for the sake of this experiment. Now, he reports that, so far, those boards have been running long-term without problems. Together with [Eben]’s comment, this instills confidence in us when it comes to our RP2040 forays and 5V inputs.

There are a number of important caveats to this, that you should read up on. Some major points – certain GPIOs (like ADC ones) can’t take it, the GPIOs aren’t 5V-tolerant when set to output, and you shouldn’t feed the GPIOs 5V when the RP2040’s VDDIO is not powered up. [Andrew] points out one such case himself – one board of his has shed all level shifters except for the 8-bit address bus, which is driven by either the CPU or the RP2040 at different times, and that would result in 5V on an output-set GPIO when contention happens. All in all, if you’re working with 5V logic and your application is more hacking than business-critical stuff, you can shed the level shifters, too.

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Kitchen timer project in a angled green 3d printed case with a 7 segment display and knob.

Printing A Brutalist Kitchen Timer

April 2, 2023 by 23 Comments

A kitchen timer is one of those projects that’s well defined enough to have a clear goal, but allows plenty of room for experimentation with functionality and aesthetics. [Hggh]’s exploration of the idea is a clean, Brutalist kitchen timer.

The case for [Hggh]’s kitchen timer is 3D printed with openings for a TM1637 four digit, seven segment display and for a KY-040 rotary encoder with knob attached. The internals are driven by an ATmega328P powered from a 18650 cell with a DW01-P battery protection chip and a TP4056 chip for charging. On the back of the case is a power switch and USB-C connector for power. It looks like the 3D printed case was sanded down to give it a smooth matte surface finish.

All the project files, including the STLs, OpenSCAD code, and KiCAD design, are available on GitHub. This Brutalist kitchen timer project is a nice addition to some of the kitchen timers we’ve featured in the past, including a minimalist LED matrix timer and a Nixie timer with keypad.

Could 1080p Video Output From The RP2040 Be Possible?

March 31, 2023 by 13 Comments

Modern microcontrollers often have specs comparable with or exceeding early gaming consoles. However, where they tend to fall short is in the video department, due to their lack of dedicated graphics hardware. With some nifty coding, though, great things can be achieved  — as demonstrated by [TEC_IST]’s project that gets the RP2040 outputting 1080p video over HDMI.

The project builds on earlier work that saw the RP2040 outputting digital video over DVI. [TEC_IST] realized that earlier methods already used up 30% of the chip’s processing power just to reach 320×240 output. To get to 1080p resolution would require a different tack. The idea involved using the 32-bit architecture of the RP2040 to output a greater data rate to suit the higher resolution. The RP2040 can do a 32-bit move instruction in a single clock cycle, which, with 30 GPIO pins, would be capable of a data rate of 3.99 Gbits/second at the normal 133 MHz clock speed. That’s more than enough for 1080p at 60 Hz with a 24-bit color depth.

Due to the limitations of the chip, though, some extra hardware would be required. [TEC_IST] has drawn up a design that uses external RAM as a framebuffer, while using shift registers and other supporting logic to handle dumping out signals over HDMI. This would just leave the RP2040 to handle drawing new content, without having to redraw existing content every frame.

[TEC_IST] has shared the design for a potential 1080p HDMI output board for the RP2040 on GitHub and is inviting comment from the broader community. They’re yet to be built and tested, so it’s all theoretical at this stage. Obviously, a lot of heavy lifting is being done off-board the microcontroller here, but it’s still fun to think of such a humble chip doing such heavy-duty video output. Continue reading “Could 1080p Video Output From The RP2040 Be Possible?” →

Cold War Military Telephones Now Usable Thanks To DIY Switch Build

March 30, 2023 by 18 Comments

The TA-1042 is the most badass looking telephone you’ll ever see. It’s a digital military telephone from the 1980s, but sadly non-functional unless it’s hooked up to the military phone switches it was designed to work with. These days, they’re really only useful as a heavy object to throw at somebody… that is, unless you had the suitable supporting hardware. As it turns out, [Nick] and [Rob] were able to whip up exactly that.

Their project involved implementing the TA-1042’s proprietary switching protocol on a Raspberry Pi Pico. The microcontroller’s unique Programmable I/O subsystem proved perfect for the task. With a little programming and a hat for the Pico to interface with the hardware, they were able to get the TA-1042 working as intended. It involved learning how to encode and decode the Manchester encoded data used by the Digital Non-secure Voice Terminal equipment. Notably, the TA-1042 isn’t the only phone you can use with this setup. You can also hook up other US military DNVT phones, like the TA-954 or TA-1035.

If you want this hardware for yourself, you can simply buy one of [Nick] and [Rob]’s DNVT switches from Tindie. Alternatively, you can roll your own with the source code provided on GitHub.

We’ve seen these phones before repurposed in an altogether different fashion. We’ve also taken a deep dive into the details of the military’s AUTOVON network.

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