Zeppelin Design Labs Altura Theremin, User Manual

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ON THE PCB
Lift the lid off your acrylic Altura case, or open the top of your card stock case, and take a look inside.
1. BATTERY HOLDER
Use a high-quality 9v DC alkaline battery, like Energizer. Do not waste your money on cheap batteries!
You will regret it. Insert the battery into the holder, and push down to snap the battery into place. You
may need to use a small screwdriver as a shoe horn to coax the battery into place.
As the battery drains, the ON LED will grow dimmer and the Altura may behave unpredictably. You are
not likely to damage anything, but it simply won’t work well. Replace the battery!
Plugging in a 9v DC power supply will disconnect the battery. It’s okay to leave the battery installed
while using an external power supply. The only concern is if you forget the battery is there and years
go by. Eventually the battery will leak acid all over your Altura, and this could damage or destroy it.
2. ISP HEADER
To the right there is a cluster of six little pins, three rows of two each. This is the In-System Programmer
(ISP) header. This is the data port you use to communicate with the microcontroller that runs the Altura.
To make use of it, you need a little device called a programmer. This
is a little circuit board with a USB cable out one end to plug into your
computer; and out the other end is a ribbon cable with a socket to plug
into the ISP header. Pin 1 of the header is the top left pin. The socket on
your programmer will have some sort of indicator on one of the corners
to indicate pin 1. Be sure to attach your programmer to the header correctly!
We used a USB-Tiny clone programmer to develop the Altura. Zeppelin Design Labs offers this
programmer as an accessory. If you obtain a programmer from another source such as Sparkfun or
Adafruit, be sure it is a USB-Tiny. Some users have had trouble with other types of programmers, such
as Arduino boards. How to use the programmer is covered in the section “Programming the Altura”.
3. ARTICULATION ADjUST
We developed the Articulation feature to improve the stability and playability of the Altura. The Altura
is driven by software running on a microcontroller, an ATmega 328PA by Atmel. Microcontroller
programs usually just run in loops as fast as they can, and they can run really fast. The left and right
sensors will “ping” hundreds of times per second if allowed to do so. Your hand is a squashy, flappy,
lumpy thing – and it is relatively small compared to the space the sensors are monitoring. As a result,
the information the sensor gets back can vary considerably from one ping to the next. When we let
the Altura use this data with no further processing, the result is a very unstable instrument: notes come
and go, or bounce around the scale at random. We use a number of clever data processing tricks to
distinguish signal from noise and stabilize the Altura’s performance. One of these tricks is to simply
slow down the loop. You will never need to play hundreds of notes per second, so why collect so much