About the Book
ST was the first silicon vendor to introduce a Cortex-M7 chip. Like the M4, the M7 has a floating point processor, and a specialized I2S peripheral called the SAI (Serial Audio Interface, I guess).
Floating point is a big help in computing envelopes for audio outputs.
The M7 also runs twice as fast as the M4.
The STM32F7-DISCO board includes an audio codec, the wm8994, and an audio output that works either for headphones or powered speakers. In addition it has a 420 x 272 touchscreen, and a TFT color LCD.
So the hardware needed for the theremin is already in place.
All that was needed was the code, which this book provides.
Writing code for modern ARM processors is sometimes a challenging activity. There are a great many modern peripherals on chip. So many in fact that there are seldom enough processor pins to accomodate all the peripherals on the chip. So only certain combinations of peripherals can be used at the same time. Each peripheral must have its clock individually configured, and there are multiple layers to the chip libraries. It is a good idea to have a completed project to use as a model.
Every detail of the development, from requirements through testing and validation is documented in the chapters of this book. All of the code included in the final product is included in this book. The information is presented with all the clarity that the author could muster.
One of several free development environments is described, along with links to the silicon vendor's design and debugging tools.
There are several possibilites for expansion of the program supplied. One might add a capability of recording and playing back tracks played on the device using a micro-sdcard slot on the board. It should be possible to add a 24dB per octave, variable cutoff, resonant filter to replace the simple smoothing filter supplied. These are left as an exercise for the reader.
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.