Embedded Development on ARM Processors
Embedded Development on ARM Processors
About the Bundle
The bundle includes How to Develop Embedded Software, GPS Tracker Project for Cortex-M3 ARM, and XY Theremin Project for STM32F7-DISCO Board.
Each book in the series gives a detailled description of an embedded software project on an ARM Cortex-M device. The descriptions include the entire lifecycle of the projects from inception to requirements analysis, through architecture, estimating, design, coding, debugging, verifying and validating the final product.
The books are written in the hope that they will provide detailled examples, including source code, and guidance for embedded software engineers as they learn to develop code on the ARM series of processors.
The author of this series has spent the last 30 years of his life developing embedded software for electronic products produced by innovative startups as well as Fortune 500 comanies.
How To Develop Embedded Software
A Case Study
This book uses an example project to illustrate each of the steps used to develop a new embedded system program.
System requirements and architecture are developed, followed by methods to estimate level of effort needed to implement them. A simple design methodology shows how to divide the system into cooperating virtual software objects, along with suggestions for their verification. Suggestions are made for coding, debugging, and verifying the virtual objects, as well as integrating them into a working program, and demonstrating the requirements have been met.
Complete source code, with makefile, is included with the purchase of the book. The attention paid to architecture and design make it easier to follow the example source code, or to make changes and add features as needed.
The source code in this book implements a digital trombone, which uses a slide potentiometer to control the note played, and an air pressure sensor with a tube into which the user blows to make and control notes. A spring-loaded on-off switch is used to choose between saw, square, triangle, or sine waveforms. The buffered DAC output is conveyed to an on-board, 3.5 mm audio jack.
The example program can be built with a free version of the GNU ARM compiler toolset on Windows, Linux, or Mac. The binary code produced can be copied to the NUCLEO-L432KC bed icon on the desktop. Or a Visual Studio Code program from Microsoft may be used to build, load and debug the program on the target board. Visual Studio Code build directories are included free with the purchase of the book.
GPS Tracker Project for Cortex-M3 ARM
The source code for this book illustrates the use of simple state machines to parse GPS NMEA sentences, and to interact with the on-board cell modem which exchanges text messages with the user's smart phone.
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 book.
A makefile is included which can build the debug or release versions of the code without using the IDE.
Source code includes a FIFO manager to handle the interrupt-driven UART interfaces to GPS and cell modem. A time converter changes GPS UTC time into Unix UTC time for use by a module which schedules transmission of position reports to the user.
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.
XY Theremin for STM32F7-DISCO
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.
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