0.4 [ mini-project ] create standard midi files with labview  (Page 10/4)

Required background

If you have not done so already, please study the pre-requisite modules, MIDI Messages and Standard MIDI Files . You will need to refer to both of these modules in order to complete this activity. Also, you will find it helpful to have already worked through the mini-project MIDI File Parsing .

Introduction

In this project you will create your own LabVIEW application that can produce a standard MIDI file. You will first develop a library of six subVIs that can be combined into a top-level VI that operates just like MIDI_UpDown.vi below (click the“Run”button (right-pointing arrow) to create the MIDI file, then double-click on the MIDI file to hear it played by your soundcard):

MIDI_UpDown.vi produces a two-track MIDI file, with one track an ascending chromatic scale and the other a descending chromatic scale. You can select the voice for each track by choosing a tone number in the range 1 to 128. You can also select the duration of each note (“on time”) and space between the notes (“off time”).

Remember, MIDI_UpDown.vi is simply a demonstration of a top-level VI constructed from the subVIs that you will make. Once you have constructed your library of subVIs, you will be able to use them in a wide array of projects; here are some ideas:

• simulated wind chime: with an appropriate voice selection (see the General MIDI Level 1 Sound Set to choose a bell-like sound) and random number generator for delta times
• bouncing ping-pong ball: write a mathematical formula to model the time between bounces and the intensity of bounces
• custom ring-tone generator for a cell phone

These are just a few ideas–be creative! Remember to take advantage of your ability to control the sound type, note-on velocity, pitch bend, etc.

Tour of the top-level block diagram

Click the image below to take a quick tour of the top-level block diagram of MIDI_UpDown.vi . The role of each subVI will be discussed in some detail, and you will have a better idea of the design requirements for each of the subVIs you will create.

Subvi library

You will create six subVIs in this part of the project. Develop them in the exact order presented! Also, make sure you test and debug each subVI before moving on to the next. Many of the concepts and techniques you learn at the beginning carry forward to the more sophisticated subVIs you develop toward the end.

The requirements for the subVIs are detailed in the following sections. Input Requirements specify the name of the front panel control, its data type, and default value, if needed). Output Requirements are similar, but refer to the front panel indicators. Behavior Requirements describe in broad terms the nature of the block diagram you need to design and build.