Tag Archives: Teensy

DIY MIDI interface for iPad version 2

I’ve finished the hardware part of my Teensy 2.0 based iPad MIDI interface project.

Getting it to fit in the smallest possible Hammond 1551 box was a challenge. I rebuilt the circuit no less than three times before getting it to fit in the the 1551H enclosure. The 8-pin opto-isolator used on the proto was replaced with a 6-pin Sharp PC900 to save space.

Update 1: Supply current is about 35mA. Not sure if this can be reduced below the 20mA limit.

Update 2: I’ve managed to get the operating current down to about 22mA without changing hardware. A simple code change – to take advantage of the idle mode when waiting for events –  saved a few milliamps. About 10mA savings comes from setting the clock to 8MHz instead of the default 16MHz.

According to the Teensy documentation, another 7mA of savings is possible using a 3.3V linear regulator IC that can be installed on the back side of the board. That should drop the operating current well below the 20mA limit.

See below for more pics and schematic.

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DIY MOTU Microlite MIDI Thru Mod

Here’s a mod for the MOTU Microlite.

Problem: I use a program called MIDI Patchbay to route/merge midi in the computer. If my Macbook is disconnected, crashed, or sleeping, my MIDI footcontroller (MFC-101) cannot control my effect/amp processor (Axe-FX) or other rack gear.

Solution: This mod adds a MIDI-thru feature to the Microlite. It is controlled by a new switch on the front panel. The switch selects between two operating modes:

Normal Mode
LED off Microlite is a 5×5 usb midi interface
Thru Mode
LED on IN1 is routed to OUT2, OUT3, OUT4, and OUT5
IN2 is routed to OUT1

Teensy 2.0
74HCT595N (get at least 2 of these)
toggle switch
1k ohm resistor
wire wrap wire
small gauge hookup wire for switch and LED
heat shrink tubing for LED and resistor

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Teensy Arduino USB Tap Tempo for Axe-FX

Here’s a simple hardware project that would be a good first-time project for anyone interested in creating their own USB MIDI device.

For this project I used a small and inexpensive USB-based microcontroller board called the Teensy 2.0. This tiny board is packed with features: 25 I/O pins, 12 analog inputs, 7 PWM outputs, 16MHz processor, USB 2.0 full-speed/low-speed, UART, SPI, and I2C.

Teensy 2.0 development board

I used the free Arduino software development platform for this project. The Arduino language is similar to C, so anyone familiar with C will feel right at home. The company that makes the Teensy provides an extension to Arduino called TeensyDuino, which adds support for the USB 2.0 port. Making a USB device could not be easier.

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