About the Book
The source code in this book implements a digital theremin, using a resistive X-Y touch screen, and a five position joy-switch for input. Its output is an analog signal consisting of a selected audio waveform, modulated by an Attack-Decay-Sustain-Release envelope triggered and updated by a finger touching the resistive touch screen.
The X axis of the touchscreen controls volume, while the Y axis controls frequency. The joy-switch controls the hardness or softness of the attack phase, and the decay rate of the envelope after the finger is removed from the screen.
Waveforms supported include square, triangle, and saw; although the waveform generation algorithm supports arbitrary single cycle waveform templates.
A free version of the GNU ARM compiler was used under Windows 7 to build the system. Startup code and Linker script were supplied by the free IDE used to develop and debug the program. Those files are included in the source code section of the book.
A makefile is included which can build the debug or release versions of the code without using the IDE.
The book is intended to convey a useful point of view on embedded system development, which will help working programmers develop their software engineering skill set.
Requirements, system architecture, and complete design documentation make it easy to follow the source code, or to make changes and add features as needed.
A collection of verification and validation tests are described, which can be used to make sure source code changes have not broken any features of the program.
About the Author
I have developed embedded software for 30 years. Along the way, I have worn out several keyboards, stared holes in multiple displays, and produced firmware for a wide variety of electronic products.
Systems developed in whole or part include: Multi-parameter biofeedback system for Apple II, C and Dsp code for a television watching robot, firmware for a laser power meter, hypertext editor and math assistant for a pocket PC, autosampler firmware for a hematology instrument, robotic control and sequencer for a genetic blood assay machine, bootloader and kernel for an oximeter, portable flight planning computer, firmware for a wireless data acquisition system for bridge diagnostics, base station firmware for corrections telemetry and alcohol monitoring, communications protocol for an implantable hearing aid, usb mass storage driver, and sensor drivers for an oilfield seismic data logger, firmware for a digital theremin and a gps locator-tracker.
For more detailed information, see www.canyoncode.com.