Digital to Analog to Digital to Analog to Digital Conversion

[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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WTF-O-meter

wtf-button

Here’s something every office probably needs. Ours does at least. It’s a WTF counter. When the office gets just a little too weird, someone hits the button and it gets logged. It’s probably pretty easy to judge the day by the WTF chart. The button is connected to an Arduino that updates the status on a local web server. We can imagine a nice bar graph of WTFs per day, or possibly a pie chart with normal time vs WTF time. Unfortunately, imagining is all we’re going to do. They didn’t include any examples of the visualizations. Can you imagine saying something to a co worker just for them to promptly march over and slap the WTF button? Maybe we don’t need one.