Commodore 64 Cynthcart

A software / hardware combo that allows for control of the analog filter inside a Commodore 64 that is running Cynthcart from a host computer (eg, Macbok, PC).

• 16-step filter sequencer
• Set the speed of the filter sequence (with intervals between values reaching 2ms)
• Set the length of the sequence from 1 to 16 beats
• Offset value allows for shifting the filter values up or down on a larger scale
• MIDI mode allows sending data directly to control the filter (this mode disables the sequencer)

Download the Max/MSP patch here:

It requires Max/MSP runtime which can be downloaded from


The hardware is very simple, and is based around an Arduino board that is using a bit-banging SPI technique to write data to a 100KΩ digital pot (model MCP42100). Approximately 7 of the 8 bits of data actually change the value of the filter (this could be due to the resistance value of the pot).

Any microcontroller that can either do SPI natively or through bit-banging should be able to handle this simple operation.

Software, schematics + code >>


~ by steelberryclones on June 27, 2008.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: