Oakley midiDAC User Manual

Oakley Sound Systems

5U Oakley Modular Series

midiDAC

Single Channel midiCV Converter

PCB Issue 4 & 5

User Manual

V5.0

Tony Allgood
Oakley Sound Systems
Carlisle
United Kingdom

The suggested front panel layout for the 2U wide MOTM format module.

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Introduction

This is the User Manual for the issue 4 and 5 midiDAC midi to CV convertor 5U module from
Oakley Sound. This document contains an overview of the operation of the unit, the midiDAC
PIC specifications and the calibration procedure.

For the Builder's Guide, which contains a basic introduction to the board, a full parts list for
the components needed to populate the boards, and a list of the various interconnections,
please visit the main project webpage at:

http://www.oakleysound.com/mididac.htm

For general information regarding where to get parts and suggested part numbers please see
our useful Parts Guide at the project webpage or http://www.oakleysound.com/parts.pdf.

For general information on how to build our modules, including circuit board population,
mounting front panel components and making up board interconnects please see our generic
Construction Guide at the project webpage or http://www.oakleysound.com/construct.pdf.

The issue 5 midiDAC fitted to a 2U wide natural finish Scheaffer panel.

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The Oakley midiDAC midi to CV convertor module

The midiDAC is a single channel midi to analogue convertor. This project is a joint
development between Oakley Sound and Trevor Page. Trevor wrote the firmware for the
processor used in this project.

The midiDAC is designed to drive any 1V/octave synthesiser or modular system. There are
eight outputs available:

Gate: +5V gate

Pitch CV: 127 steps of 12 bit accurate pitch voltage conforming to 1V/octave

(trimmable). Pitch bend is added to this signal and the maximum bend
interval (up to one octave) can be adjusted from the bend depth control.

Velocity: 0 to 10V proportional to midi note on velocity.

Pitch Bend: -5V to +5V proportional to pitch bend wheel position. 0V corresponds to a

centred wheel.

Modulation: 0 to 10V proportional to modulation wheel position.

Aftertouch: 0 to 10V proportional to midi channel aftertouch.

CC # 100: 0 to 10V proportional to midi controller number 100.

Legato: This signal goes to +5V when two notes are played at the same time. This

can allow slides to be activated at will; TB303 style. An optional external
switch may be used to override the automatic activation of slide. Slide may be
turned off by transmitting the standard midi glide/slide command.

Also featured on the circuit board itself is a 3-way header to directly feed the Oakley ‘CV­gate’ bus on the Dizzy board.

The design also features a midi thru circuit which is greatly improved on the previous issue
midiDAC designs. The processor used in this project is a PIC16F628 running at 4 MHz.

Please note: this product does not support the use of V/Hz or linear VCOs. These are found
on some Yamaha and Korg analogue products, and just one Roland, the SH-2000.

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