My Profile Photo

Internet of Me by Jerad Acosta


A place to reference, recite, rinse and repeat my efforts, failures, thoughts and progress, delusions and regressions, but mostly a sandbox for whoever I am at the moment. Perhaps I'll occasionally enjoy the reminiscing with the castles or taking census of the endless games of tic-tac-toe etched in my box.


Arduino and C Programming Class Notes

These are notes for The Arduino Platform and C Programming.

Class Reading

Module 3 Lecture Notes

Arduino Toolchain and setup

  1. Arduino Build Process
  2. setup() Function
  3. loop() Function
  4. pinMode() Function
  5. digitalWrite() Function
  6. digitalRead() Function
  7. analogRead() Function

Arduino Toolchain and Upload process:

  • code
    • Write Code / Program in Arduino IDE
  • Verify
    1. Combine & Transform (code) –>
    2. Compile –>
    3. Link (libraries) –>
    4. Hex File Creation
  • Upload
    • (5) Upload .hex file to Arduino board

Combine and Transform

  • All program files are combined into one
  • An #include is added to reference basic Arduino libraries
  • Function prototypes are added
    • Every function has a prototype that defines things like type for variable inputs and return types
  • A main() function is created
    • every C and C++ program needs a main
    • The main is created behind the scenes here based on the setup() and loop()
  • avr-gcc is invoked to cross-compile the code
    • Resulting code executes on AVR, not Intel
  • Generates an object file (.o file)
  • Object file is linked to Arduino library functions (that are being used)

After you have combined the different source files into one you’ve transformed them adding the main() including the libraries, then you cross-compile the code.

Compilation is taking the C or C++ code and generating the machine code required to execute the actual program - because the processor only understand machine code and not high level languages we program in. Cross-Compilation is when you compile code on one machine for execution on another machine. Here we are compiling code on our Intel processor based laptops or desktops that is intended to be executed on AVR processor in the Arduino boards.

Compilation produces an object file (.o file) that is compiled but not complete because it still needs to be Linked.

Linking is taking the object (.o) files and combining them. This includes object files for libraries. When functions from other libraries are used in the code, a branch or jump statement needs to be inserted to jumps you to the libraries code. When Compiling you do not know where in the library a function is. During the linking process the object files from your code and the libraries code make this more explicit by creating those precise jumps in the executable.

Hex File Creation and Programming

  • avr-objcopy is invoked to change the format of the executable file
  • A .hex file is generated from the .elf file

After compiling and linking is finished, you get an .elf file which is an executable file. BUT, the Arduino processor does not accept .elf files. So avr-objcopy is used to change .elf file to another executable file that can be used by the Arduino processor. This is the .hex file.

Module 4 Debugging using the Serial Interface

Module 4 Reading

Serial Communication with the Arduino

Module 4 Lecture Notes

Debugging comes after you have written your code and something inevitably fails to run the first time you attempt to run it.

You should expect to spend a lot of time debugging code. In-fact, a safe rule-of-thumb is that debugging takes about twice as long as writing the code in the first place.

Debug and Trace

Controllability

  • Ability to control sources of data used by the system
  • Input pins, input interfaces (serial. ethernet, etc)
  • Registers and internal memory

Observability

  • Ability to observe intermediate and final results
  • Output pin, output interfaces
  • Registers and internal memory

Controllability and observability are required

In addition to controllability you need observability Observability is the ability to observe intermediate and final results The first thing you need to observe are the output pins. Either an actuator like an LED or a multimeter reading the outpudect of a particular pin. If the pin is changing states quickly you may want to use an oscilloscope to view a change in voltage over time.

Debug Environments

Remote Debugger Host is the computer on which you are writing Target an external embedded system - in this case the Arduino board - on which code to be debugged is run on

Remote Debug Pros and Cons Advantages

  1. Good run control using breakpoints to stop execution
  2. Debug monitor can alter memory and Registers
  3. Perfect functional accuracy

Disadvantages

  1. Debug interrupts alter timing so real-time monitoring is not possible
  2. Need a spare communication channel
  3. Need program in RAM (not flash) to add breakpoints

Embedded Debug Interface Debug logic that is built into the processor. Does Debug activities and is BuildProcess

  • Many modern processor include
  • Works
  • A few dedicated pins have to be added for

Pros

  1. Faster

Module Quizzes

Quiz 2

  1. What is the name of the library which contains the printf() function? stdio.h

  2. What does the ‘\n’ character mean? newline

  3. What type of data is surrounded by double quotes in a program? a string

  4. What C type is one byte long? char

  5. Does the following statement evaluate to True or False? (10 || (5-2)) && ((6 / 2) - (1 + 2)) becomes: (10 || 7) && (3 - 3) –> (True OR True) AND False

  6. What does the following program print to the screen?
    int main (){
    int x = 0, y = 1;
    if (x || !y)
      	printf("1");
    else if (y && x)
      	printf("2");
    else
      	printf("3");
    }
    
  7. What does the following program print to the screen?
    int main (){
    int x = 0, z = 2;
    while (x < 3) {
      	printf ("%i ", x);
       x = x + z;
     }
    }
    
  8. What does the following program print to the screen?
    int foo (int q) {
     int x = 1;
     return (q + x);
    }
    int main (){
    int x = 0;
    while (x < 3) {
      	printf ("%i ", x);
       x = x + foo(x);
     }
    }
    

Quiz 3

  1. What is the function of the linking process after compilation?
    It merges the libraries with the application code into a single executable.
  2. What is the role of avrdude?
    It writes the executable into the memory of the Arduino
  3. Why are classes (in C++) useful?
    They improve the organization and understandability of the code
  4. What is one way that a sketch can invoke a function contained inside a class?
    The name of the class can be concatenated with the name of the function, with a period in between.
  5. Which of the following statements is true?
    The setup() function is executed once and the loop() function is executed iteratively, as long as the Arduino is powered on.
  6. True of False: An analog pin can accept analog inputs and drive analog outputs?
    False; analogRead() uses the Arduino board 10-bit Analog to Digital converter. This enable mapping of input voltage between 0 and 5 volts to integer values between 0 and 1023. There is no analog output supported by the Arduino in any of its pins including the analog outputs.
  7. If a sketch running on an Arduino UNO executes the following statements, what voltage would be expected on pin 1 afterwards?
    pinMode(1, OUTPUT);
    digitalWrite(1, HIGH);
    

    5

  8. True or False: The delay() function cases program execution to pause for a number of milliseconds?
    True

Quiz 4

  1. Which of the following does NOT provide observability in a system?
    • A switch connected to an Arduino input pin
  2. What is meant by the expression “run control of the target”?

The ability to control the inputs to the target microcontroller

The ability to control the outputs of the microcontroller

The ability of the target microcontroller to control its own inputs

  • The ability to stop and start the execution of the target microcontroller

WRONG3. What is NOT an advantage of using a remote debugger?

Remote debugging allows good run control

Remote debugging requires an extra communication channel for debugging

Remote debugging allows control of registers and memory

  • Remote debugging provides excellent functional accuracy

WRONG4. What is NOT a feature of an embedded debug interface?

Extra pins are needed to support debugging

Breakpoints and watchpoints are supported

Automatic test generation is commonly supported

  • On-the-fly memory access is supported
  1. What is NOT an advantage of the UART protocol?
    A shared clock is not required
  • Fewer wires are needed for communication as compared to a parallel protocol

Fewer pins are needed than using a parallel protocol

Higher data transfer rates are typically achieved compared to a parallel protocol

  1. Which of the following statements is NOT true about the UART protocol?
    The bit duration is determined by the baud rate

The bit duration is the inverse of the baud rate

The baud rate is the maximum number of transitions per second

The data transmission rate is equal to the baud rate

  1. Synchronization is performed in the UART protocol based on the timing of the Start bit. True or False?
    • True

False

  1. An error in bit transmission (perhaps dye to noise) may not be detected, even if a parity bit is used. True of False?
    • True

False

Student Peer graded Assignments

Week 1: Program a blinking LED on an Arduino board

Week 2: Create a Fibonacci Printing Program

/* Write a program in C that computes and prints out the first six digits
in the Fibonacci sequence. You will need to look up the definition of
the Fibonacci sequence if you don't know it.
The first two numbers in the sequence are 0 and 1,
but your program should compute the next four digits.
Your C program must compile in order for it to be tested. */

#include <stdio.h>
int main() {
  /*variable for how many numbers in the sequence should be printed*/
  int seq = 6;

  /*create secquence array*/
  int fib[seq];

  /*the first two outputs are 0 and 1*/
  fib[0] = 0;
  fib[1] = 1;
  printf("Digit #1 of the Fibonacci sequence is %d \n"
         "Digit #2 of the Fibonacci sequence is %d \n", fib[0], fib[1]);

  /*run a loop to collect the remaining seq - 2 numbers in the sequence*/
  for (int i = 2; i < seq; i++) {
    fib[i] = fib[i - 1] + fib[i - 2];
    printf("Digit #%d of the Fibonacci sequence is %d\n", i + 1, fib[i]);
  }

  return 0;
}

Week 3: Alternate between Fast and Slow flashing Pin 13 LED

Write a program that causes the built-in LED connected to pin 13 on the Arduino to blink, alternating between fast blinks and slow blinks. The LED should blink 5 times, once every half second, and then it should blink 5 more times, once every two seconds.

/*
 This code used the Blink example that comes with the Arduino IDE
 It was modified to accomidate a University of Irvine class requirement
 as part of the IoT programming certification via Coursera

  modified 17 August 2016
  by Jerad Acosta
 */


// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin 13 as an output.
  pinMode(13, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  // create loop with 5 blinks at 1 per half second
  // 1/4 second on amd 1/4 second off gives one blink per half second
  for(int i = 0; i < 5; i++) {
    digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(250);              // wait for 1/4 of a second
    digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
    delay(250);              // wait for 1/4 of a second
  }
  // create loop with 5 blinks at 1 per 2 seconds
  // 1 second on and 1 second off gives 1 blink per 2 seconds
  for(int i = 0; i < 5; i++) {
    digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(1000);              // wait for 1 second
    digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
    delay(1000);              // wait for 1 second
  }
}

! References: ¡Left Blank Intentionally! below here in the source code are reference links that can be reused throughout the article. ###TODO Check if you can use reference links from other posts without reciting them on each page ¿can there be ‘Global’ reference links - or image sources - that can be used on multiple pages?

comments powered by Disqus