An attempt at Arduino

I've always wanted to fool around with electronics. Particularly, I've been wanting to fool around with microcontrollers since it seems awesome to program things that don't live entirely within a RAM chip, but directly interact with "the outside world". The problem is, I never know where to start.  I actually programmed some basic ATMEGA stuff when I was a student, but it was under a rushed research environment and I had time enough only to get things thrown together, put it in a box, and move on without thinking too much about it.

I kept hearing about this thing called Arduino. which seems to be a good place to start. Utilizing an upcoming birthday, I hinted heavily to my wife that the perfect gift for a geek like me was a "get your feet in the water" Arduino kit. My pressing hints payed off and I've just started fooling around with my new Arduino Uno.

Upon first glance, Arduino seems pretty awesome. It is a composite microcontroller/programming board which gives you easy access to a number of digital/analog i/o pins. Despite the convenience of this, I was initially put off by this. During my brief stint with AVR programming, I could remove my little ATMEGA chip, and stick it in a small box containing a 9V battery and a tiny breadboard and have my device. If I wanted to make a couple, I just needed the ICs, and not several copies of the programmer, which scales up the size and cost of a duplicate project.

I have this dream of placing a bunch of ICs on a breadboard for individual projects, rather than chunking together a bunch of Arduinos. However, discussions such as this one have convinced me that under the hood, an arduino is simply a special  a AVR programmer, and if I wanted to, I could use the arduino board to program AVR chips just the same. So for now, I'm sold, and am excited to get started.

Apparently, the equivalent of "hello world" in the microcontroller world is to blink an LED, so that was my first step. I found a quick tutorial on this and, as is my habit, tried to modify it a little from the get go. As a first selling point to Arduino, it was about three minutes from opening the box to getting a simple program running.

The first step was to download the Arduino software which allows you to either debug, or upload your program with the click of a button. The next step was to wire up a simple circuit board to do my bidding. The idea for this first program is simple: When the user clicks a button, slowly ramp up the voltage to an LED from whatever it was to a maximum value. When the button is pressed again, it slowly ramps down to 0.

The code for this is simple: A button press toggles the state of the device between on and off. When its on(off) the device increments(decrements) the brightness (which is just a PWM voltage) and delays for 10 ms. That's pretty much it. There is a bit of weirdness of the switch bouncing which can be remedied by introducing a slight delay after switching states:

const int aLED = 9;        // Analog LED
const int BUTTON = 7;      // Push Button
boolean buttVal = 0;       // True if button pressed
boolean buttValOld = 0;    // Value from last cycle

boolean on = false;        // Stores the state' of the device

int brightness = 0; // Stores the brightness value from 0 to 255

void setup()
{
  pinMode(aLED, OUTPUT); // Set pin9 for output
  pinMode(BUTTON,INPUT); // Set pin 7 for input
}

void loop()
{
// Handle a button press. If the state has changed, delay for 5ms 
// to avoid bouncing
  buttVal = digitalRead(BUTTON);
  if(buttVal&&!buttValOld)
  {
    on = !on;
    delay(5);
  }
  buttValOld = buttVal;
  
  if(on)  // If state is on, ramp up voltage each cycle, then delay
  {
    if(brightness<255)
    {
      brightness++;
      delay(5);
    }
  }
  else  // If state is off, ramp down voltage each cycle, then delay
  {
    if(brightness>0)
    {
      brightness--;
      delay(5);
    }
  }
// Finally, set the LED voltage to the current value of 'brightness'
  analogWrite(aLED,brightness); 
}

The circuit itself is also is exceedingly simple: depressing the switch routes 5V to the input pin 7, which causes digitalRead(BUTTON) to return a "HIGH" state. The LED voltage is run through a 270 Ohm resistor to ground to limit the current drawn from output pin 9.

The result .... is pretty much what you'd expect:

I had a lot of fun with this one and am looking forward to the next mini project-ling.