digital to analog

3 Articles

High-Resolution MIDI Controller

January 5, 2024 by 20 Comments

For an older standard, MIDI has remarkable staying power in the music industry. It remains the de facto digital interface between computers and instruments thanks to its open nature, but its age does show a little bit. Sending control change (CC) messages, for example, was originally designed to fit within seven bits, which doesn’t give particularly fine resolution compared to more capable modern computers. To work around that, a fourteen-bit message is possible, doubling the resolution, and this MIDI interface uses this larger amount of data to send these high-resolution CC messages.

The 14-bit messages are actually fairly well documented but are a bit obscure, with very limited hardware support. To that end, [Gero] set about building this control interface to solve that problem. It’s made up of only eight knobs, each of which is mapped one-to-one to a parameter on the computer, allowing the interface to feel more like an analog device where the knob corresponds directly to a change in an aspect of the sound. The platform is built around a Teensy 4.0 and some multiplexers to handle all of the knobs, with the open source software available for anyone to use to modify their actions. [Gero] was aiming for high fidelity for all aspects of this controller, not just the improved digital resolution, and made a number of other improvements to it as well like re-greasing the potentiometer knobs and a custom 3D printed enclosure.

All of the software is available for use, as well as the files to print the case. [Gero] is also working on a PCB to make the construction of the device a little more streamlined, but for now, it requires a bit of soldering off-the-shelf parts together. The MIDI standard is open as well, which allows for a lot of innovation in the creation of musical instruments from unique hardware. This project builds a MIDI synthesizer with parts from a Sega Genesis.

ESP32, We Have Ways To Make You Talk

February 6, 2018 by 24 Comments

One of our favorite scenes from the [James Bond] franchise is the classic exchange between [Goldfinger] and [Bond]. [Connery] (the One True Bond) says, “You expect me to talk?” And the reply is, “No Mr. Bond, I expect you to die!” When it comes to the ESP32, though, apparently [XTronical] expects it to talk. He posted a library to simplify playing WAV files on the ESP32. There is also a video worth watching, below.

Actually, you might want to back up to his previous post where he connects a speaker via one of the digital to analog converters on the board. In that post, he just pushes out a few simple waveforms, but the hardware is the same setup he uses for playing the WAV files.

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Digital To Analog To Digital To Analog To Digital Conversion

January 3, 2015 by 9 Comments

[Andy] had the idea of turning a mixing desk into a MIDI controller. At first glance, this idea seems extremely practical – mixers are a great way to get a lot of dials and faders in a cheap, compact, and robust enclosure. Exactly how you turn a mixer into a MIDI device is what’s important. This build might not be the most efficient, but it does have the best name ever: digital to analog to digital to analog to digital conversion.

The process starts by generating a sine wave on an Arduino with some direct digital synthesis. A 480 Hz square wave is generated on an ATTiny85. Both of these signals are then fed into a 74LS08 AND gate. According to the schematic [Andy] posted, these signals are going into two different gates, with the other input of the gate pulled high. The output of the gate is then sent through a pair of resistors and combined to the ‘audio out’ signal. [Andy] says this is ‘spine-crawling’ for people who do this professionally. If anyone knows what this part of the circuit actually does, please leave a note in the comments.

The signal from the AND gates is then fed into the mixer and sent out to the analog input of another Arduino. This Arduino converts the audio coming out of the mixer to frequencies using a Fast Hartley Transform. With a binary representation of what’s happening inside the mixer, [Andy] has something that can be converted into MIDI.

[Andy] put up a demo of this circuit working. He’s connected the MIDI out to Abelton and can modify MIDI parameters using an audio mixer. Video of that below if you’re still trying to wrap your head around this one.

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