INTERNET OF THINGS: ARDUINO AND C PROGRAMMING

COMBINING THE TANGIBLE AND THE VOLATILE INTO ONE

Punit Goswami

ARDUINO ENVIRONMENTTHE ARDUINO BOARD, ITS SOFTWARE COMPONENT AND OTHER ADD-ON HARDWARE

ARDUINO DEVELOPMENT BOARD• Eight bit microcontroller – brain of the board

• USB Port – to communicate with the desktop/laptop

• USB controller chip – manages USB transferred data

• IO pins – board’s connection to the outside world

• Quartz oscillator – board’s time keeper

• Reset button – taking the board back to its initial state

• External power jack – power from dedicated source

Co-axial jack, but USB can also be used

INPUT/OUTPUT PINS (I/O PINS) Top and bottom rows of the board Holes in the board which we can stick wires in Holes are connected to the chips through traces on-board 14 Digital I/O pins on top [0-13]

Highs – 5 volts Lows – 0 volts Max Current - 40 mA 6 Analog input pins on the bottom [A0 – A5] Power output pins on the bottom [ 5v , 3.3 v ] Reset pin to reset the board to initial state

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MICROCONTROLLERS Two microcontrollers on the board

Main ATmega328 – 8 bit microcontroller

User programmable, runs user-written application code Carries firmware, like bootloader

ATmega16U2

Handles the communication with the USB interface, not directly accessible

STORAGE & MEMORY

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Non-volatile flash memory for storage

32 kilobytes in size

Static Random Access Memory (SRAM) for memory (volatile)

3 kilobytes in size

CLOCK

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16 MHz clock speed ~ 16 million operations per second

Helps synchronize all components together

Keeping track of occurrence of events

PROGRAMMING FIRMWARE

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The ISCP headers can be used to program the firmware on the board

ICSP1 for the main ATmega328 microcontroller

ICSP2 for the ATmega16U2 microcontroller

Special equipment are required in order to re-program the firmware through these headers

SOFTWARE ENVIRONMENT

• Arduino IDE – Integrated Development Environment

• Can be programmed using other IDEs too, like Eclipse

• Arduino IDE is more versatile

• Needs no special drivers or additional components

• Available for Windows, Linux and Mac

• Cross compiler – compiles for a different target platform than the one being programmed on

IDE – SOFTWARE TOOL FOR PROGRAMMING File operations and other general options on top

Buttons for most commonly used options (Verify, Upload, etc.)

Main window – Text editor for writing code

Message area – for messages to the programmer

OPTIONS BUTTONSButtons on the top have the most common ,useful operations

Verify – compiles the code and checks for errors

Uploads – compiles the code, uploads it to the board. Works only if the board is connected

New – creates a new sketch, a new program

Open – opens an existing sketch

Save – saves the current sketch in the directory of your choice

Serial Monitor – opens window to communicate with the board

TARGET PLATFORM

• ATmega328 – Arduino Uno’s processor

• Arduino shields – add on hardware for specific purposes

• Shields need no complicated circuitry – prewired

• Stacks of shields on top of the Arduino

• Prefabricated libraries of methods

ARDUINO SHIELDSThe prominent reason that Arduino got so popular

Additional hardware to do particular, complex tasks

Form of separate boards

Pre-wired pins that stick into holes in Arduino

Stack on top of the Arduino to make connections

Pre-written functions for operations of these boards

Open-source designs in most of the cases, third party

Complete list of shields at http://www.shieldlist.org

OPEN SOURCE

• Hardware – the board’s design is open source

http://www.arduino.cc

• Software – the IDE is open source, written in Java, modifiable, redistributable

• Open source community – easily available codes and help on troubleshooting

SETTING UP THE ENVIRONMENTLEARNING TO CODE IN C/C++ FOR ARDUINO

RUNNING IDE ON WINDOWS Emacs or NotePad++ text editor

Gcc C compiler

The debugger, gdb

IDE provides one-stop solution

ARDUINO IDE Require Java Runtime Environment Write codes in general C language

setup() – Initiates the variables and sets up device instances loop() – Runs the code that contains operations and

manipulations, iterates infinitely

BLINK LED EXAMPLE Pin 13 is represented by numeral 13

digitalWrite() writes voltage values to pins

delay() sets delays in milliseconds

HIGH – 5v LOW – 0v

ARDUINO PROGRAMS AND THE BUILD PROCESSHOW IT IS SAME BUT DIFFERENT TO CODE FOR THE BOARDS

Source code

Executable file Hex file Uploaded

to board

ARDUINO TOOLCHAIN

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Steps taken post code authoring

Source code(sketch) is compiled to an executable format

Executable file is linked with libraries and interpreted into a hex file

Hex file is uploaded to board

Starts executing right away

CROSS COMPILATION

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Compile on one machine, but the target is another machine. E.g.: compiling it on an Intel processor, compiling it for an AVR processor

avr-gcc – C compiler for AVR targets, gives a *.o file

avr-lnk – links library object files, results in a *.elf file

avr-objcopy – change the *.elf file into Arduino compatible *.hex file

DEBUGGING AND TROUBLESHOOTINGREMOVING ERRORS AND TAKING CARE OF REPAIR AND MAINTENANCE

DEBUGGING

• Finding reasons of erroneous execution or failure of execution

• Software problems

• Require ‘controllability’ and ‘observability’

• Controllability: the ability to control sources of data that are used by the system

Allows to do testing to test certain circumstances that might be causing a bug or triggering a bug at any rate

• Observability: the ability to observe intermediate and final results

An oscilloscope, multi-meter, or the serial monitor could be used

REAL TIME MONITORING

• Includes dynamic observation of the target and its state

• Viewing data about the execution as it occurs

• Not intrusive in terms of performance

• Important for timing constraint IoT systems

• Provides timing and functional accuracy

REMOTE DEBUGGING

Remote Debugger

• Host computer acts as debugger for a code that runs on the remote target system

• Host computer are also the systems that the programmer programs on

• Host provides the platform to interface with the debugging environment.

• Provides good run control, not good for testing timing

Embedded Debug Interface

• Seen in modern processors, Arduino and its likes have trace macrocells

• Built in to the processor

• Hardware dedicated to do debugging directly

SERIAL PROTOCOLS FOR DEBUGGING

• UART: Universal Asynchronous Receiver/Transmitter, an old protocol, still useful though.

• Low hardware overhead

• Transmits at 9600 baud

• START and STOP buts are used for synchronization

• The bits in between a START bit and the next STOP bit is the data

• To distinguish, the receiver samples at 16 times higher rate than the baud rate

• Serial interface can be used to both send data to and from the Arduino board