C[omp]ute

From: andrew cooke <andrew@...>

Date: Sat, 19 Oct 2013 21:40:18 -0300

Took and Arduino course today.  It's incredibly simple / easy (you really
don't need a course - just buy one, read http://arduino.cc, install and run
the software, and play at flashing on and off the LED)

Anyway, here are some example programs.  I was about to close the windows and
wasn't sure where to save them...



This one flashes the built-in LED with the bit pattern in ASCII "andrew".  If
you connect up a second LED (with series resistor) to O/P 12 then it is in
anti-phase.

  #define led 13
  #define other 12

  char *name = "andrew";
  long interval = 100;

  void setup() {                
    pinMode(led, OUTPUT);
    pinMode(other, OUTPUT);
  }

  void loop() {
    for (int i = 0; i < strlen(name); ++i) {
      int bit = 1;
      for (int j = 0; j < 8; ++j) {
	if (bit & *(name+i)) {
	  digitalWrite(led, HIGH);
	  digitalWrite(other, LOW);
	} else {
	  digitalWrite(led, LOW);
	  digitalWrite(other, HIGH);
	}
	bit <<= 1;
	delay(interval);
      }
    }
  }


The above couples the flashing to the main loop, which is a nuisance if you
want to do multiple things in parallel with different timing / rates.  So the
next program decouples that and flashes the two LEDs at different
frequencies.

  #define led1 13
  #define led2 12
  int value1 = HIGH, value2 = LOW;
  long interval1 = 300, prevMillis1;
  long interval2 = 400, prevMillis2;

  void setup() {
    prevMillis1 = millis();
    pinMode(led1, OUTPUT);
    prevMillis2 = millis();
    pinMode(led2, OUTPUT);
  }

  void loop() {
    if (millis() - prevMillis1 > interval1) {
      value1 = !value1;
      prevMillis1 = millis();
      digitalWrite(led1, value1);
    }
    if (millis() - prevMillis2 > interval2) {
      value2 = !value2;
      prevMillis2 = millis();
      digitalWrite(led2, value2);
    }
  }


Finally, a program that reads from the analog input and varies the LED
flashing.  I eventually had this so that a POT controlled basic rate, but a
light-sensitive resistor could reduce the rate and a push switch fix the LED
permanently on.

The serial output lets you see what range of values are being read so that you
can adjust the mapping approrpiately.

  int ledPin = 13;
  int potPin = A3;
  int potVal;
  int period = 500;

  void setup() {
    pinMode(ledPin, OUTPUT);
    Serial.begin(9600);
  }

  void loop() {
    potVal =  analogRead(potPin);
    Serial.println(potVal);

    potVal = constrain(map(potVal, 400, 600, 0, period), 0, period);
    Serial.println(potVal);
    digitalWrite(ledPin, HIGH);
    delay(potVal);
    digitalWrite(ledPin, LOW);
    delay(period-potVal);
  }


Course was at Santiago MakerSpace - http://stgomakerspace.com/ - who have a
couple of 3D printers (never seen one before in the flesh).

Andrew