Rob Toulson

Chapter 1 – Embedded Systems, Microcontrollers, and ARM

Basic concepts of the microprocessor, microcontroller, and embedded system are introduced in this chapter. The key features of an embedded system, including its hardware and software elements, and of an embedded system are introduced. An example embedded system is outlined in the form of a vending machine. Appropriate programming languages are reviewed, notably C and C++, and the overall embedded development cycle is surveyed. A history of ARM is outlined, together with a review of its products and design philosophy. The ARM Cortex microprocessor core is introduced.

Advanced rapid prototyping in small research projects with Matlab/Simulink

The following topics are discussed: Matlab for data analysis and rapid algorithm development; model based design with Simulink; scripting efficiency with Matlab/Simulink; advanced Matlab scripting; and auto-code generation for rapid prototyping.

Chapter 15 – Hardware Insights: Clocks, Resets, and Power Supply

Two of the most fundamental hardware things to manage when applying microcontrollers are power supply and clock source. This chapter investigates in some detail the way that power is supplied to the mbed and LPC1768, and how the clock source can be selected and manipulated. This clock source setting then has a major impact on power supply. Developing from this, there is a major section on low-power operation, and the use of batteries. Linked to these is how program execution is launched, either after power-up or major discontinuity; this leads to concepts of reset, watchdog timer and brownout. As the mbed itself is not designed for power-conscious applications, the chapter ends with an introduction to the Gecko Zero application board, which is based around the ARM M0+ processor core, is mbed enabled, and intended for extreme low-power applications.

Chapter 3 – Digital Input and Output

This chapter reviews some fundamental concepts of digital electronic interfacing. It introduces the mbed digital input/output capabilities, along with the necessary application programming interface library elements. A simple C program which controls the mbed digital output is introduced, and its essential features are reviewed. This leads to consideration of further C features, including simple constructs like while, if, for, and switch. The interfacing requirements between the mbed and switches and light emitting diodes are considered, including voltage and current considerations. This is then extended to optosensors, seven-segment displays, and transistor interfacing to larger DC loads. By the end of the chapter the reader will be ready to write simple mbed programs in C, which will interface with a range of digital input/output elements, applying circuits using both the breadboard and the mbed application board.

Chapter 2 – Introducing the mbed

This chapter introduces the “mbed microcontroller” itself. It considers the form and design of the mbed, including its connection to a host PC through a USB link, its sources of power, and how it can be plugged into a larger system. The chapter looks in overview at the LPC1768 microcontroller at the mbeds heart. It views this microcontrollers design at a block diagram level and notes its different features, including its use of the ARM Cortex core and its wide range of peripherals. The chapter goes on to explain how to set up an mbed account, access the compiler, and compile and run a first example program. The mbed application board is also introduced.

Chapter 7 – Starting with Serial Communication

This chapter introduces the main concepts of serial data communication, including Master, Slave, clock, and the shift register. It distinguishes between synchronous and asynchronous serial forms. It introduces the features of a serial peripheral interface (SPI) link, and how this can be applied using two mbeds communicating with each other. As an advance on SPI, the inter-integrated circuit bus (I2C) is introduced. Again, the principles are illustrated by linking two mbeds. The advantages and disadvantages of SPI and I2C are evaluated. Concepts of asynchronous serial communication are introduced, and an asynchronous data link between the universal asynchronous receiver/transmitter (UART) ports of two mbeds is established. The use of UART to link mbed and host computer is explained. At a more sophisticated level, universal serial bus is introduced, and simple mbed applications explored.

Chapter 11 – Wireless Communication – Bluetooth and Zigbee

This chapter introduces concepts and applications relating to wireless data communication. It starts with a review of the principles, including the electromagnetic spectrum, radio transceivers, protocols and antennae. The background to short distance, personal area network protocols is introduced, through reference to IEEE Working Groups. Bluetooth is introduced, and trialled using the RN-41 Bluetooth module. The RN-41 is used to develop key Bluetooth concepts. Simple PC-to-mbed, and mbed-to-mbed Bluetooth links are demonstrated. The Zigbee protocol, its typical networks and applications are introduced. XBee radio modules are used to illustrate simple Zigbee links, in Transparent mode. Use of the XBee in its more flexible API mode is then introduced, which opens the door to more advanced Zigbee applications.

Chapter 16 – Developing Commercial Products With mbed

This chapter gives an overview of the development cycle for embedded systems products. The process of moving from ideas, through proof-of-concept development and onto design-for-manufacture and commercialization are discussed. Alternative mbed platforms are discussed, particularly considering low-cost boards that can be incorporated directly into niche products. Products requiring thousands of units to be manufactured will benefit greatly from the design of a bespoke printed circuit board that can be developed as a stripped down version of the mbed platform—allowing prototype software and hardware to be merged directly into a mass-manufacture design. Programming the LPC1768 chip directly is discussed alongside a case study description of the Irisense Excelog touch screen temperature logger, which was built and successfully commercialized utilizing the mbed platform.

Chapter 14 – Letting Go of the mbed Libraries

This chapter explores use of the control registers within the LPC1768 microcontroller. It uses these to configure and access peripherals direct, without use of the mbed libraries. The chapter explores use of digital input/output, DAC, and ADC in this way. In general, it replicates the capability of programs given in earlier chapters. Once the control registers are understood, however, there is greater flexibility on offer, at the cost of far greater complexity, and the danger of introducing errors which are difficult to find. In configuring the peripherals, consideration is also given to registers which control more global features of the microcontroller, including some aspects of power and clock selection.

Chapter 9 – Interrupts, Timers, and Tasks

This chapter explores aspects of timeliness in embedded systems and how they are addressed in the ARM mbed. The interrupt mechanism applied in the mbed is explored, and simple interrupt-driven programs developed. Further aspects of interrupts are considered, including latency, and the use of more than one interrupt sources. The concept of the digital counter is reviewed, notably in its application as a timer. The mbed timers are applied, first in simple form, and then to implement timeout and periodic interrupts. C coding techniques are developed further, including the generation of pseudorandom numbers. Practical applications include the implementation of an mbed-based metronome, and the use of accelerometer-generated interrupts. Methods for switch debouncing are also discussed and evaluated.