XO106r5/Squascillator firmware IC

A firmware IC for the XO106r5 and/or Squascillator modules - although the source code is readily available, some people lack the skill or inclination to burn their own firmware ICs. For those people, we've got you covered.

The stock firmware is fairly simple - a voltage controlled square wave oscillator with voltage-controlled duty cycle as well. The output is a PWM waveform which will need to be filtered - a simple RC low-pass filter (1k/100nF) does the job, but feel free experiment.

If you're building up an XO106r5 from a PCB/panel set then you will need four of these ICs. The discontinued Squascillator module only requires a single IC.

The firmware is flashed to a through-hole (DIP-8) ATTiny85 microcontroller, which can also be used as part of a breadboard layout. The IC pinouts are as follows:

• Pin 1: RESET - connect to +5V via a 10k resistor
• Pin 2: PW - duty-cycle control voltage (input)
• Pin 3: CV - pitch control voltage (input)
• Pin 4: GND
• Pin 5: Unused
• Pin 6: PWM output (output)
• Pin 7: FINE - fine-tune CV (input)
• Pin 8: VCC (5.5V absolute max)

The source code for this firmware is available on GitHub: https://github.com/yorkmodular/xo106r5/blob/master/src/squascillator.ino