Week 9: Embedded Programming

This week's tasks:

• Group assignment:
  • Comparing the performance and development workflows for other architectures
  • Link to the Group Assignment Page
• Individual assignment:
  • Reading a microcontroller data sheet
  • Programming our board to do something

Challenges:

• Reading a 286 pages document, which is not just a story but a difficult concept to grasp is quite challenging and it was not possible for me. I read some introductions from the document. I decided to use and edit a ready code and also use this data sheet as a reference for understanding the parts of the code.
• I first installed Atmel Studio 7 because I wanted to reuse a C code. But I found it a bit challenging for me. So some students suggested Arduino. I read about it and browesed some code samples. And I found Arduino platform simpler to go ahead with.
• Understanding how to match the pins of my sketch with Atiny44 and Arduino was a bit challenging at the first.
• I added a video to this page using iframe, and I wanted to find a way that video plays muted when the page is uploaded. But I couldn't find a solution for it. Any suggestions?
  Actually a not brilliant solution was using the video as instagram story, which gives you the option of muting the video and then saving the video and reusing it unmuted :-D

Considerations:

• Short version of the data sheet

Technology used:

• Atmel Studio 7.0 Software
• Arduino 1.8.5

ATtiny44A

Pinout of ATiny44A. (pictures are screen shots from the data sheet)

Editing a Program

I decided to re-use the code written by Antti and Jani. Their program reads the state of the button connected to I/O pin PA7 to control the state of the LED connected to I/O pin PB2.
/*
 * Fabhellobutton.c
 *
 * Created: 11.3.2016 8:46:20
 * Author : anttim
 */
#include <avr/io.h>
int main(void)
{
    DDRB |= (1 << PB2);        // with OR-operation set bit number 2 in DDRB register, make it output
    DDRA &= ~(1 << PA7);    // clear bit number 7 in DDRA register,  make it input, shift 1 left by seven, 10000000, AND with one's complement 01111111
        /* Replace with your application code */
    while (1)
    {
        if (PINA & (1 << PINA7)){    // with AND-operation check if bit 7 is  set
            PORTB |= (1 << PB2);    // with OR-operation set bit number 2 in PORTB
        } else  {
            PORTB &= ~(1 << PB2);    // with AND-operation clear bit number 2  in PORTB
        }
    }
}

Analyzing the code

First, I tried to understand the elements of the code.

#include <avr/io.h>

• "This header file includes the apropriate IO definitions for the device that has been specified by the -mmcu= compiler command-line switch." (reference)

int main(void)

• A function that expects no arguments and returns an integer.

DDRB

By refering to the data sheet and also google serach, I figured out that:

DDRA

Bit Operations

&, |, ^, >>, <<, ~

• | bit OR
• & bit AND
• ~ bit NOT
• ^ bit EXLUSIVE OR (XOR)
• << bit LEFT SHIFT
• >> bit RIGHT SHIFT

For DDRB |= (1 << PB2);    AND DDRA &= ~(1 << PA7);   : We change 0’s to 1’s and 1’s to 0’s: then we do bitwise and: then to register. I made the following tables (picture format) to show the analysis more in detail:

Arduino

After reading about Arduino, I assumed it as an easy-to-use platform. So I decided to give it a try. So I went through getting started guide, and did as following:

• In order to be able to write programs and also to upload the programs to my borad I had 2 options:
  1. Using online IDE (The Arduino Software)
  2. Working offline and using desktop IDE.
• I decide to use online IDE. So I signed up and created an account.
• To use online IDE, I followed these Instructions.
• From Built-In Examples (file > examples > digital > Button), I found the following piece of code that turns on the LED when one press the button:

• // constants won't change. They're used here to set pin numbers:
  const int buttonPin = 2;     // the number of the pushbutton pin
  const int ledPin =  13;      // the number of the LED pin
  
  // variables will change:
  int buttonState = 0;         // variable for reading the pushbutton status
  
  void setup() {
    // initialize the LED pin as an output:
    pinMode(ledPin, OUTPUT);
    // initialize the pushbutton pin as an input:
    pinMode(buttonPin, INPUT);
  }
  
  void loop() {
    // read the state of the pushbutton value:
    buttonState = digitalRead(buttonPin);
  
    // check if the pushbutton is pressed. If it is, the buttonState is HIGH:
    if (buttonState == HIGH) {
      // turn LED on:
      digitalWrite(ledPin, HIGH);
    } else {
      // turn LED off:
      digitalWrite(ledPin, LOW);
    }
  }