Hackaday Links: September 24, 2017

This is it. After twelve years we finally have a new Star Trek. Star Trek: Discovery (we’re using ST:DSC as the abbreviation) is airing right about when this post goes up. Next week, you’ll have to pay CBS $6USD a month to get your Star Trek fix, and today might be the last time a new episode of Star Trek is aired on broadcast TV ever. Enjoy it now, and hope the theme song doesn’t have lyrics. Also, hope The Orville is a tenth as good as a Galaxy Quest series could be.

What’s the best way to describe Delta Sigma PLLs? The Cat In The Hat (PDF, page 31). [Dr. Tune] found a Seuss reference in a TI app note. Personally, I’m a fan of hand-drawn cartoons, but we’ll take what we can get.

This weekend the Prusa I3 MK3 was announced. A good printer just got better. Now here’s the video.

The Raspberry Pi is a great media storage device, but it’s absolutely insufficient for audiophile tomfoolery. Here’s a neat Pi DAC/amp/DSP thingy. The VoltaStream turns the Raspberry Pi into a WiFi-connected pair of speakers with low-latency audio in and a TOSLINK connector.

SpaceX! There is serious consideration being given to starting an ‘Elon Musk column’ here on Hackaday. There will be SpaceX updates coming this week from the International Astronautical Congress in Adelaide. What will we find out? I don’t know bruh, but I just got back from Burning Man and I realized it was a whole lot like Mars and I was wondering Elon, like, have you ever been to Burning Man because it’s really dusty and a whole lot like Mars and there’s not much water… Please, organizers of the IAC, I implore you: give more idiots microphones. That was hilarious.

How was the World Maker Faire in New York this weekend? In one word, empty. Abnormally so. Maker Faire was not as crowded as last year, and you could actually move around. My agoraphobia didn’t kick in until the afterparties, and lines for the $5 bottles of water were short. Bay Area Faire attendance was down 16% from 2016-2017, and I would bet attendance for the NY Faire would be down a similar amount. Even a 10% decline in attendance would be noteworthy; the weather last year was cold and rainy and this year was beautiful. There are rumors, speculation, and people wondering how long Maker Faire will continue, but except for Intel pulling out of the maker market, no actual information. Millennials are killing the Maker Faire industry?

Repurposing Moving Coil Meters to Monitor Server Performance

Snazzy analog meters can lend a retro flair to almost any project, but these days they often seem to be retasked as indicators for completely different purposes than originally intended. That’s true for these Vu meters repurposed as gauges for a Raspberry Pi server, and we think the build log is as informative as the finished product is good-looking.

As [MrWunderbar] admits, the dancing needles of moving-coil meters lend hipster cred to a project, but getting his Vu meters to cooperate and display network utilization and disk I/O on his Raspberry Pi NAS server was no mean feat. His build log is full of nice details on how to measure the internal resistance of the meter and determine a proper series resistor. He also has a lengthy discussion of the relative merits of driving the meters using a PWM signal or using a DAC; in the end, [MrWunderbar] chose to go the DAC route, and the video below shows the desired rapid but smooth swings as disk and network usage change. He also goes into great depth on pulling usage parameters from psutil and parsing the results for display on the meters.

Looking for more analog meter goodness? We saw a similar CPU load meter a few months back, and there was this mash-up of Nixies and old meters for a solar energy CEO’s desk.

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Hackaday Trims Its Own Resistors

There are times when you might want an odd-value resistor. Rather than run out to the store to buy a 3,140 Ω resistor, you can get there with a good ohmmeter and a willingness to solder things in series and parallel. But when you want a precise resistor value, and you want many of them, Frankensteining many resistors together over and over is a poor solution.

Something like an 8-bit R-2R resistor-ladder DAC, for instance, requires seventeen resistors of two values in better than 0.4% precision. That’s just not something I have on hand, and the series/parallel approach will get tiresome fast.

Ages ago, I had read about trimming resistors by hand, but had assumed that it was the domain of the madman. On the other hand, this is Hackaday; I had some time and a file. Could I trim and match resistors to within half a percent? Read on to find out.

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VGA Without A Microcontroller

One of the most challenging projects you could ever do with an 8-bit microcontroller is generating VGA signals. Sending pixels to a screen requires a lot of bandwidth, and despite thousands of hackers working for decades, generating VGA on an 8-bit microcontroller is rarely as good as a low-end video card from twenty years ago.

Instead of futzing around with microcontrollers, [Marcel] had a better idea: why not skip the microcontroller entirely? He’s generating VGA frames from standard logic chips and big ‘ol EEPROMs. It works, and it looks good, too.

VGA signals are just lines and frames, with RGB pixel values stuffed in between horizontal sync pulses, and frames stuffed between vertical sync pulses. If you already know what you want to display, all you have to do is pump the right bits out through a VGA connector fast enough. [Marcel] is doing this by saving images on two parallel EEPROMs, sending the output through a buffer, through a simple resistor DAC, and out through a VGA connector. The timing is handled by a few 74-series four-bit counters, and the clock is a standard 25.175 MHz crystal.

There’s not much to this build, and the entire circuit was assembled on a breadboard. Still, with the clever application of Python to generate the contents of the ROM, [Marcel] was able to build something that displays eight separate images without using a microcontroller.


MIDI DAC for Vintage Synth Hacks

A lot of classic synthesizers rely on analog control voltages to vary parameters; this is a problem for the modern musician who may want to integrate such hardware with a MIDI setup. For just this problem, [little-scale] has built a MIDI-controllable DAC for generating control voltages.

It’s a simple enough build – a Teensy 2 is used to speak USB MIDI to a laptop. This allows the DAC to be used with just about any modern MIDI capable software. The Teensy then controls a Microchip MCP4922 over SPI to generate the requisite control voltages. [little-scale]’s video covers the basic assembly of the hardware on a breadboard, and goes on to demonstrate its use with a performance using the MIDI DAC to control a Moog Mother 32 synth. [little-scale] has also made the code available, making it easy to spin up your own.

We can see this project being indispensable to electronic musicians working with banks of modular synths, making it much easier to tie them in with automation in their DAW of choice. This isn’t the first MIDI interfacing hack we’ve seen either – check out this setup to interface an iPad to guitar pedals.

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An Eye-Catching Raspberry Pi Smart Speaker

[curcuz]’s BoomBeastic mini is a Raspberry Pi based smart connected speaker. But don’t dis it as just another media center kind of project. His blog post is more of a How-To guide on setting up container software, enabling OTA updates and such, and can be a good learning project for some. Besides, the design is quite elegant and nice.

boombeastic_02The hardware is simple. There’s the Raspberry-Pi — he’s got instructions on making it work with the Pi2, Pi2+, Pi3 or the Pi0. Since the Pi’s have limited audio capabilities, he’s using a DAC, the Adafruit I2S 3W Class D Amplifier Breakout for the MAX98357A, to drive the Speaker. The I2S used by that part is Inter-IC Sound — a 3 wire peer to peer audio bus — and not to be confused with I2C. For some basic visual feedback, he’s added an 8×8 LED matrix with I2C interface. A Speaker rounds out the BoM. The enclosure is inspired by the Pimoroni PiBow which is a stack of laser cut MDF sheets. The case design went through four iterations, but the final result looks very polished.

On the software side, the project uses Mopidy — a Python application that runs in a terminal or in the background on devices that have network connectivity and audio output. Out of the box, it is an MPD and HTTP server. Additional front-ends for controlling Mopidy can be installed from extensions, enabling Spotify, Soundcloud and Google Music support, for example. To allow over-the-air programming, [curcuz] is using resin.io which helps streamline management of devices that are hard to reach physically. The whole thing is containerized using Docker. Additional instructions on setting up all of the software and libraries are posted on his blog post, and the code is hosted on GitHub.

There’s a couple of “To-Do’s” on his list which would make this even more interesting. Synced audio being one: in a multi-device environment, have the possibility to sync them and reproduce the same audio. The other would be to add an Emoji and Equalizer display mode for the LED matrix. Let [curcuz] know if you have any suggestions.

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Hybrid Raspberry Pi + PIC32 = Oscilloscope and Function Generator

The PicBerry is a student final project by [Advitya], [Jeff], and [Danna] that takes a hybrid approach to creating a portable (and affordable) combination digital oscilloscope and function generator. It’s based on the Raspberry Pi, features an intuitive Python GUI, and can generate and measure simultaneously.

But wait! The Raspberry Pi is a capable little Linux machine, but meeting real-time deadlines isn’t its strong suit. That’s where the hybrid approach comes in. The Pi takes care of the user interface and other goodies, and a PIC32 over SPI is used for 1 MHz sampling and running a DAC at 500 kHz. The idea of combining them into PicBerry is to get the best of both worlds, with the Pi and PIC32 each doing what they are best at. The readings are sent in batches from the PIC32 to the Pi, where the plot is updated every 30 ms so that user does not perceive any visible lag.

The project documentation notes that improvements can be made, the speeds are a far cry from regular bench equipment, and the software lacks some typical features such as triggering, but overall not bad at all for under $50 of parts. In fact, there are hardly any components at all beyond the Raspberry Pi, the PIC32, and a MCP4822 digital-to-analog converter. A short demo video is embedded below.

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