Turns an ATtiny85 into a "noise chip" suitable for an analogue drum machine such as LDB-1.
One of the pins outputs digital "white" noise using a linear feedback shift register, 4 other pins output different square waves out of tune with each other.
The noise is used by the snare drum, clap and hi-hat modules, while sqaure waves are used to add a bit of metallic tembre for the hi-hat.
Note that the frequencies of the square waves are not described in the article, but there is a reference to a schematics of Boss DR-110 where each of these square wave modules is made using 2 inverters with a 4.7nF capacitor being charged via 82K, 120K, 330K, and 220K resistors. My crude calculation shows that the corresponding frequencies are: 1049Hz, 717Hz, 261Hz, 392Hz.
Measuring the actual frequncies out of the ATtiny85 you get the following (hat tip to @zumdar):
- Pin 0: 960 Hz
- Pin 1: 673.5 Hz
- Pin 2: 248 Hz
- Pin 4: 369 Hz
- Pin 5: Noise