Many everyday objects have become embedded, connected and even autonomous. The engineers and technicians who develop them must have skills in both computer science and electronics.
Drawing on some 20 years of experience in the field of hardware and embedded computing, Programming of Embedded Systems analyzes how physical objects can interact with microcontrollers. It presents the fundamental principles of programming and code structuring. Although based on a specific family (STM32) of microcontrollers, the various chapters outline general concepts applicable to any microcontroller. They analyze the mechanisms that govern exchanges between a computer program and a hardware component of the embedded object.
Each chapter details the programming of peripheral units and ends with an example using a common application for managing the heating of a home equipped with a photovoltaic installation to illustrate implementation in the programming language C.
Table of Contents:
Preface xi
Chapter 1 Aims, Context and a Guiding Thread Example 1
1.1. Aims of this book 1
1.2 What this book contains and what it does not 2
1.3. About the code examples 3
1.4. Choosing your μcontroller: the STM32 family 3
1.4.1. Criteria when choosing a μcontroller 4
1.4.2. STM32 family 5
1.4.3. STM32F10x line 6
1.5. Guiding thread example 8
1.5.1. Context: photovoltaic self-consumption installation 8
1.5.2. System: optimization of electric heating in a photovoltaic self-consumption household 10
1.5.3. Summary of the peripherals seen in the guiding thread example 13
Chapter 2 General Programming Principles 15
2.1. Pointers and registers 15
2.1.1. “Simple” variables 15
2.1.2. Pointer to a variable 16
2.1.3. Using pointers to pass arguments to functions 18
2.1.4. When to use a pointer? 20
2.1.5. Function pointers 21
2.2. C language structure and usage in the STM 32 22
2.2.1. Structured type organization 22
2.2.2. Accessing registers via a structure 24
2.3. Case of nested structures 25
2.4. Masks usage 27
2.4.1. General considerations 28
2.4.2. Masks for setting bits to 1 29
2.4.3. Masks for setting bits to 0 30
2.4.4. Bit inversion 31
2.4.5. Extension and generalization to bit field assignment 31
2.5. Code structuring and the concept of drivers 33
2.6. Interrupt routines 36
2.6.1. Handler routines concepts 36
2.6.2. Interrupt routine implementation 37
2.6.3. Redirection via dynamic programming 39
Chapter 3 General STM32F10x Hardware Considerations 43
3.1. Global STM32 architecture 43
3.2. Cortex-M3 components 44
3.3. Clock trees and RCC units 47
3.3.1. Generation of primary clocks 47
3.3.2. Generation of secondary clocks 49
3.3.3. RCC unit programming 51
3.3.4. RCC unit configuration coding example 55
3.4 Watchdogs 57
3.4.1 Independent watchdogs 58
3.4.2 Windowed watchdogs 59
Chapter 4 Binary Inputs/Outputs (I/O): Parallel Ports 61
4.1. Concept of I/O ports 61
4.2. Electronic aspect 62
4.2.1. Global architecture 63
4.2.2. Input configuration 65
4.2.3. Output configuration 66
4.3. STM32 GPIOs 67
4.3.1. Configuration registers 69
4.3.2. Access registers 70
4.4. Example 73
4.4.1. Proposed solution 75
4.4.2. Comments 80
4.5. Unaddressed points regarding GPIOs 81
Chapter 5 Interrupt and DMA Management 83
5.1. General exceptions and particular interrupts 83
5.2. Resets and interrupt vector tables 84
5.2.1. Stack pointers and program counters 84
5.2.2. IVT contents 85
5.3. Principle of redirection and the role of the NVIC 88
5.3.1. Nvic 88
5.3.2. Conditions for an interrupt to be accepted 90
5.3.3. Priority management 92
5.3.4. Redirection process steps 96
5.4. Case of external interrupt inputs 96
5.4.1. AFIO and EXTI peripherals 97
5.4.2. NVIC level 98
5.4.3. GPIO and AFIO levels 99
5.4.4. EXTI level 102
5.5. Guiding thread example: treating an EXTI exception 103
5.5.1. Problem to solve 103
5.5.2. Proposed solution 103
5.6. Direct memory access 105
5.6.1. Generalities 105
5.6.2. DMA on the STM32F10x 106
5.7. Guiding thread example: case of DMA programming 111
5.7.1. UART configuration 112
5.7.2. DMA configuration 112
5.7.3. Program structure 112
Chapter 6 Timers 115
6.1. General information on counters or Timers 115
6.1.1. Basic principle 116
6.1.2. Timer units in the STM32F10x 116
6.1.3. Different types of Timers 117
6.2. Operating modes 118
6.2.1. General structure of a Timer 119
6.2.2. Core block: overflow, events and frequency 120
6.2.3. Capture/Compare block 125
6.2.4. Trigger controller block and encoder interface 129
6.2.5. Master mode 139
6.3. An additional Timer: the SysTick 141
6.4. Guiding thread example 143
6.4.1. Case study: a control knob 143
6.4.2. Code extract 143
Chapter 7 Pulse-Width Modulation (PWM) 145
7.1. Generalities on PWM-type signals 145
7.1.1. Definition 145
7.1.2. Use in information transmission 147
7.1.3. Use in digital-to-analog conversion 148
7.2. Implementation of PWM in an STM32F10x µcontroller 154
7.2.1. Basic operation 154
7.2.2. Configuration and options 156
7.3. Guiding thread example 160
7.3.1. First possible solution 160
7.3.2. Second adopted solution 160
7.3.3. Interrupt configuration 160
7.3.4. The PWM configuration itself 161
7.3.5. The GPIO configuration 161
7.3.6. Code excerpt 161
Chapter 8. Analog to Digital Converter 165
8.1. Generalities and operating principles 165
8.1.1. Role and definitions 165
8.1.2. Successive-approximation ADC 168
8.1.3. Variable voltage measurement 169
8.1.4. Multi-channel ADC 172
8.1.5 Overview of the ADC timings 173
8.2. ADC in the STM32F10x 174
8.2.1 Simplified architecture of the ADC 174
8.2.2. ADC functional modes 181
8.2.3. DMA with ADC 185
8.3. Application: the power analyzer 186
8.3.1 Determining the sampling duration T s 186
8.3.2. Code excerpt for configuration 187
Chapter 9. Some Communication Buses 191
9.1. Introduction 191
9.2. UART units 193
9.2.1. Generalities 193
9.2.2. Reading/writing techniques 195
9.2.3. UART configuration on the STM32F10x 197
9.3. SPI units 203
9.3.1. Generalities 203
9.3.2. Shift register-based read/write techniques 205
9.3.3. SPI configuration on the STM32F10x 209
9.4. I 2 C bus 213
9.4.1. Generalities 213
9.4.2. Electrical topology of the I 2 C bus 215
9.4.3. Principle and protocol 216
9.4.4. Reading/writing techniques 220
9.4.5. I 2 C configuration on the STM32F10x 224
9.5. Guiding thread example 233
9.5.1. UART reception in interrupt mode 233
9.5.2. Temperature measurement via the I 2 C bus and DMA 234
Chapter 10. STM32 Power Management 241
10.1. Introduction 241
10.2. Domains of the µcontroller 242
10.2.1 1.8V Domain 242
10.2.2 V DD Domain 244
10.2.3 Backup Domain 244
10.2.4 V DDA Domain 245
10.3. Reset on STM 32 245
10.3.1 System Reset 245
10.3.2 Power Reset 247
10.3.3 Backup Domain Reset 247
10.3.4. Reset flags (RCC_CSR) management 247
10.3.5. STM32F10x reset summary 248
10.4. RTC registers 249
10.4.1 Secure access to the Backup Domain 250
10.4.2. RCC_BDCR registers 250
10.4.3. RTC register structure 251
10.4.4. Reading/writing RTC registers 252
10.5. Low Power modes 254
10.5.1. Event and interrupt 254
10.5.2. Key bits for Low Power modes 255
10.5.3. Sleep mode 258
10.5.4. Stop mode 259
10.5.5. Standby mode 260
10.6. Software architecture and using Low Power modes 261
10.6.1. Classical software architecture 261
10.6.2. Sleeping in main(), WFI instruction 262
10.6.3. Automatic sleep upon interrupt exit 262
10.6.4. Sleeping in main(), WFE instruction 264
10.6.5. Standby mode on RTC alarm 264
10.7. Guiding thread example for Low Power mode 264
10.7.1. Problem to solve 264
10.7.2. Proposed solution 265
Appendix 271
References 283
Index 285
About the Author :
Vincent Mahout is Lecturer at INSA Toulouse, France, where he teaches automation and hardware and embedded computing.
Thierry Rocacher is Associate Professor of Electrical Engineering at INSA Toulouse, France, where he teaches electronics and embedded computing.
Guillaume Auriol is Associate Professor of Electrical Engineering at INSA Toulouse, France, where he teaches electronics and embedded computing.
