Microcontrollers

• A microcontroller (MCU) is a small computer on a single integrated circuit consisting of a relatively simple central processing unit (CPU) combined with peripheral devices such as memories, I/o devices, and timers.
• A microprocessor incorporates the functions of a computer’s central processing unit (CPU) on a single integrated circuit.
• Things that matter:

  • Peripherals
  • Concurrency & Timing
  • Clock Rates
  • Memory sizes (SRAM & flash)
  • Package sizes
• Types of Microcontrollers:

  • Bits
  • Memory/devices
  • Instruction set
  • Memory Architecture
• Bits - 4 / 8 /16/ 32
• Memory/devices - Embedded/External
• Instruction set - CISC/RISC
• Memory architecture - Princeton/Harvard
• Metrics we need to consider:

  • power consumption
  • Clock frequency
  • IO pins
  • Memory
  • Internal functions
  • Others
• Power Consumption - We cannot afford mA MCU because the power budget of the system is 3.47 mA.
• Clock Frequency - (speed that instructions are executed)

  kHz is too slow…

  100MHz is over kill…
• IO pins (interface for external peripherals) - Interfacing sensors, UART debugger, LEDs, Bluetooth. Analog pins (input/output analog signal e.g., audio). Digital pins (input/output digital signal e.g., busses, GPIOS)
• Program (non-volatile) - logic to read from sensors, communicate
• Stack - functions calls are now expensive (no recursion)
• Data - constants (time periods), Sensor history, Communication state.
• Memory - We need to have sufficient memory to store: Program (non-volatile), Stack, Data
• Internal Functions - Migrating data from the sensor to the radio (DMA)
• Memory - Store accelerometer history data.
• Internal Memory (MCU) - RAM 0.5 - 128 kBytes
• External Memory (MCU) - Flash, high power consumption, 5mA for read and ~10mA for erase.
• Components of Microcontroller:

  
  

  • Program memory
  • RAM
  • A/D Converter
  • Microprocessor
  • Oscillator
• I/O Devices (Sensors)

  • Keyboard
  • Mouse
  • Microphone
  • Scanner
  • Video/Photo Camera
• Large Diversity - Many widely differing device types. Devices within each type also differs.
• Speed - varying, often slow access & transfer compared to CPU. Some device-types require very fast access & transfer.
• Access - Sequential VS random, read, write, read & write.
• What operations does software need to perform on peripherals?

  • Get and set parameters
  • Receive and transmit data
  • Enable and disable functions
• How can we imagine providing an interface to hardware from software?

  • Specialized CPU instructions (x86 in/out)
  • Treating devices like they are memory (MMIO)
• Port I/O - Devices registers mapped onto “ports”; a separate address space. Use special I/O instructions to read/write ports.
• Memory Mapped I/O - Device registers mapped into regular address space. Use regular move (assignment) instructions to read/ write a device’s hardware “registers”.
• Microcontroller Families:

  • 8051
  • Motorola
  • PIC
  • Texas
  • National
  • ARM
  • Others
• Family under 8051:

  • Intel
  • Atmel
  • Dallas
  • Philips
  • Siemens
• Sketches - Arduino programs are called sketches and are written using the Arduino Integrated Development Environment (IDE).
• Two Main Functions of Sketch:

  • setup()
  • loop()
• setup() - this function is called once when the arduino board starts up. It is used to initialize variables, pin modes, and other configurations.
• loop() - this function runs repeatedly after setup () is executed. It contains the main code that controls the behavior of the arduino board.
• Variables - In arduino used to store and manipulate data. They must be declared with a specific data type before use.
• Common Data Types

  int - integer

  float - floating-point number

  bool - boolean

  char - character
• Comments - used to explain code logic to make it more readable. Single line comments starts with // and multi-line comments are enclosed between /* and /*
• Libraries - collections of pre-written code that provide additional functionality. It can be included in arduino sketches to simplify the implementation of complex features and interact with various sensors, actuators, and other components.
• Control Structures:

  • if statement - executes a block of code if a certain condition is true
  • else statement - executes a block of code if a certain condition is false
  • for loop - repeats a block of code a specific number of times
  • while loop - repeats a block of code while a certain condition is true
  • do-while loop - repeats a block of code at least once and continues while a certain condition is true.
  • switch-case statement - executes different blocks of code based on the value of a variable.