MIDItio

From Stm32World Wiki
Jump to navigation Jump to search
MIDItio Rendering

MIDItio is a planned USB Midi to CV device. The device will act as a USB MIDI device connected to a USB host. It will be able to run two channels simultaneously with a CV indicating the pitch and a Gate indicating start and stop.

The name MIDItio is derived from MIDI and the Latin "ditio" which means "control".

Planned features are:

  • USB MIDI Gadget/Device
  • 2 MIDI channels
  • Dual pitch CV output (1V/oct)
  • Dual gate output

Hardware Design

MCU

The primary concerns dictating the choice of MCU are:

  1. Built-in USB
  1. Built-in Digital to Analogue converters (DAC) - preferably 2
  1. Cost

The STM32L151 fits the bill nicely.

Output Amplifier

Without a boost regulator the highest available voltage on the board is the USB VBUS 5V. That means the output amplifier for the CV's need to map 0-3.3V into 0-5V.

A = 5 / 3.3. = 1.515

The amplification of a non-inverting opamp is:

A = 1 + Rf / R2

If we choose R2 = 9.1 k, we can calculate Rf

Rf = (A - 1) * R2 = 0.515 * 9.1 k = 4.68 k

A Rf of 4.7 k should do nicely.

Schematics

MIDItio rev. a schematic.svg

Renderings

Miscellaneous Links