KiwiSDR Vs RaspberrySDR — A Tale Of Two SDRs

September 30, 2020 by Al Williams 45 Comments

Once you move away from the usual software defined radio (SDR) dongles, you have only a few choices unless you want to drop some serious cash. One common hobby-grade SDR is the KiwiSDR. This popular unit runs Linux and can receive up to 30 MHz. The platform uses a dedicated A/D converter, an FPGA, and BeagleBone computer. Success of course breeds imitators, and especially when you have an open source design like the Kiwi, you are going to find similar devices with possibly different end goals. That’s how the RaspberrySDR came to be. This is a very similar unit to the KiwiSDR but it uses a Raspberry Pi, along with a handful of other differences. What’s different? [KA7OEI] tells us in a recent blog post.

Other than the obvious difference of the computer and all that it entails, the RaspberrySDR has a higher speed A/D (125 MHz vs 66 MHz) and 16-bits of resolution instead of the Kiwi’s 14 bits. This combines to give the Raspberry a wider receive range (up to 60 MHz) and — in theory — better performance in terms of dynamic range and distortion.

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An Elegant Modular Enclosure System For The Raspberry Pi 4

September 28, 2020 by Danie Conradie 45 Comments

[NODE] has been experimenting with Raspberry Pi servers and mini computers for a long time, and knows all too well how the wiring can quickly turn into a rat’s nest. His latest creation is the Mini Server version 3, a modular enclosure system for the Raspberry Pi 4, is designed to turn it into practical computing box.

The basic enclosure is a 92 mm x 92 mm x 26 mm 3D printed frame with a custom PCB top cover. One of the main goals was to collect all the major connectors on one side and make the micro SD slot easily accessible. To do this [NODE] created a set of custom PCB adaptors to route the USB-C and an HDMI port to the same side as the other USB ports, and move the micro SD slot to the bottom of the enclosure. A low profile adaptor was also designed to connect a mSATA SSD to one of the USB 3 ports, and there is space inside the enclosure for one or two cooling fans. Unlike previous version of the mini server, no hardware modifications are required on the Pi itself.

The only downside that we can see is that it doesn’t allow external access to the GPIO ports, but the entire project is open source specifically to allow people to make their own modifications.

[NODE] is a big fan of turning Raspberry Pis into custom computing devices, ranging from small terminal devices and pocket servers, to complete laptops.

Internet Connected E-Paper Message Board

September 25, 2020 by Rich Hawkes 16 Comments

Are you still writing notes on paper and sticking them to the fridge like it’s the ’80s? Well, if you are, and you read this site, you’d probably like to upgrade to something a bit more 21st century. And, thanks to robot maker [James Bruton], you can leave your old, last century, message taking behind as he has a tutorial up showing you how to build an internet connected e-paper message display board. And, if you have a Raspberry Pi, an e-paper display and adapters just lying around doing nothing, then this project will cost you less than the buck that paper and a magnet will cost you.

Sarcasm aside, this is a pretty nice project. As mentioned, the base of this is a Raspberry Pi – [James] uses a Pi 4, but you could get away with an older, lower powered model as well. This powers the cheap(-ish) e-paper display he found online, which comes with the necessary adapters for the Pi, as well as a python library to write to the display. [James] uses a Google Sheet as the cloud storage for the message board, and there is some python code to access the cells in the Sheet and print them on the display if anything has changed. A cron job runs the script every 5 minutes to catch changes in the messages.

As with most of the projects that [James] does, he gives a good overview in the video and goes over the process of finding the hardware and writing and updating the script. He’s put the script and details as well as the CAD file for the frame he created for the project up on GitHub. [James] has been featured several times on the site before, check out some of his projects.

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Adding MIDI To A Mini Synth Is Easy As Pi

September 21, 2020 by Kristina Panos 11 Comments

There are a handful of relatively dirt cheap synths out there like the KORG Monotron, but many of them use ribbon controllers that aren’t very precise. Ribbon controllers basically slide pots that you operate with your finger or a stylus. They’re painted to look like piano keys in order to show you approximately where the notes are supposed to be. The Stylophone is another extremely affordable synth that does even less as a synthesizer and uses this type of input. It’s a fun input if you don’t mind imprecision, but can be annoying otherwise.

[schollz] isn’t satisfied to synth this way, so they added MIDI input to their KORG Monotron using a Raspberry Pi and a DAC. Fortunately, the Monotron is quite the hackable little synth, with nice, big, labelled pads on the PCB.

All it really took was a couple of solder joints in the right places, plus a clever Python script. The script listens for MIDI input from a keyboard, and then controls an MCP4725 DAC, which sends voltages to the Monotron. [schollz] wrote a tuning function that computes the FFT of the MIDI tones to find the fundamental frequencies of each to send along to the Monotron. Check it out after the break.

If liquid control is what you’re after but all you have is a keyboard, try making your own ribbon controller.

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Into The Belly Of The Beast With Placemon

September 17, 2020 by Brian McEvoy 11 Comments

No, no, at first we thought it was a Pokemon too, but Placemon monitors your place, your home, your domicile. Instead of a purpose-built device, like a CO detector or a burglar alarm, this is a generalized monitor that streams data to a central processor where machine learning algorithms notify you if something is awry. In a way, it is like a guard dog who texts you if your place is unusually cold, on fire, unlawfully occupied, or underwater.

[anfractuosity] is trying to make a hacker-friendly version based on inspiration from a scientific paper about general-purpose sensing, which will have less expensive components but will lose accuracy. For example, the article suggests thermopile arrays, like low-resolution heat-vision, but Placemon will have a thermometer, which seems like a prudent starting place.

The PCB is ready to start collecting sound, temperature, humidity, barometric pressure, illumination, and passive IR then report that telemetry via an onboard ESP32 using Wifi. A box utilizing Tensorflow receives the data from any number of locations and is training to recognize a few everyday household events’ sensor signatures. Training starts with events that are easy to repeat, like kitchen sounds and appliance operations. From there, [anfractuosity] hopes that he will be versed enough to teach it new sounds, so if a pet gets added to the mix, it doesn’t assume there is an avalanche every time Fluffy needs to go to the bathroom.

We have another outstanding example of sensing household events without directly interfacing with an appliance, and bringing a sensor suite to your car might be up your alley.

TOBOT Is Your Tic Tac Toe Opponent With A Bad Attitude

September 16, 2020 by Al Williams 4 Comments

[3dprintedlife] is apparently a little bored. Instead of whiling away the time playing tic tac toe, he built an impressive tic tac toe robot named TOBOT. The robot uses a Rasberry Pi Zero and a Feather to control a two-axis robot arm that can draw the board and make moves using a pen. It also uses a simple computer vision system to look at the board to understand your move, and it has a voice too.

The other thing TOBOT has is a bad attitude. The robot wants to win. Badly. Check out the video below and you’ll see what we mean.

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This Ruggedized Raspberry Pi Was Built To Be Copied

September 14, 2020 by Tom Nardi 24 Comments

Over the last couple of years, we’ve seen a wave of impressive rugged mobile computing devices based on the ubiquitous Raspberry Pi. Sometimes they involve repurposing an existing heavy duty enclosure, and in others the Pi takes up residence in a 3D printed case which may or may not be as strong as it appears. In either event, they usually don’t lend themselves to duplication because of the time and expense involved in tracking down or printing all the parts required.

But the Raspberry Pi Quick Kit by [Jay Doscher] may change that. It represents what must surely be the simplest and fastest route to a building a rugged mobile ARM computer for your hacking adventures. Beyond the Pelican 1150 case that serves as the outer enclosure, you only need three printed parts and a handful of fasteners to complete the build. Of course you’ll need a Raspberry Pi and the official touch screen as well, but that’s sort of a given.

Electronics mounted to the 3D printed frame.

All of the electronics mount onto the three piece 3D printed frame, which is then press-fit into the opening of the Pelican case. Since you don’t need to pop any holes through the case itself, the assembled unit remains water and air tight. While [Jay] has recently shown off a very impressive 3D printed Pi enclosure, there’s really no beating a legitimate heavy duty storage case if you’re trying to protect the hardware.

When you want to use the Pi, just open the case and plug your power and accessories into the panel mount connectors under the display. There’s no integrated battery or keyboard on this build, but considering how small it is, that shouldn’t really come as a surprise.

[Jay] is targeting the Pi 4 for the Quick Kit, so that means WiFi and Bluetooth will come standard without the need for any external hardware. It looks like there might just be enough room to include an RTL-SDR receiver inside the case as well, but you’ll need to do a little redesigning of the 3D printed parts. If you do modify this design to pack in a few new tricks, we’d love to hear about it.

The Quick Kit is a greatly simplified version of the Raspberry Pi Recovery Kit that [Jay] unleashed on an unsuspecting world late last year. We’ve seen numerous variations on that original design sprout up since then, so we’re very interested to see what the response will be like to this much cheaper and easier to build version.