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INTERNET OF THINGS:ARDUINO AND CPROGRAMMINGCOMBINING THE TANGIBLE AND THE VOLATILE INTO ONEPunit 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 sourceCo-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

MICROCONTROLLERS Two microcontrollers on the board Main ATmega328 – 8 bit microcontrollerUser programmable, runs user-written application codeCarries firmware, like bootloader ATmega16U2Handles the communication with the USB interface, notdirectly accessible

STORAGE & MEMORY Non-volatile flash memory for storage 32 kilobytes in size Static Random Access Memory (SRAM) for memory (volatile) 3 kilobytes in size

CLOCK 16 MHz clock speed ~ 16 million operations per second Helps synchronize all components together Keeping track of occurrence of events

PROGRAMMING FIRMWARE The ISCP headers can be used to program the firmware onthe board ICSP1 for the main ATmega328 microcontroller ICSP2 for the ATmega16U2 microcontroller Special equipment are required in order to re-program thefirmware 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 onlyif 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 partyComplete list of shields at http://www.shieldlist.org

OPEN SOURCE• Hardware – the board’s design is open sourcehttp://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, gdbIDE 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 andmanipulations, 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

SourcecodeExecutablefileHex fileUploadedto boardARDUINO TOOLCHAINSteps taken post code authoring Source code(sketch) is compiled to an executable format Executable file is linked with libraries and interpreted into ahex file Hex file is uploaded to boardStarts executing right away

CROSS COMPILATIONCompile 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 systemAllows to do testing to test certain circumstances that might be causing a bug or triggering a bug atany rate• Observability: the ability to observe intermediate and final resultsAn 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 DEBUGGINGRemote 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 timingEmbedded 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

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