Day 6: (Mon Sep 16) Event Loop Programming

Notes for 2019-09-16. See also the Fall 2019 Calendar.

Notes from Day 5

Thoughts on demo 2: it is easier to make things more complicated than simple. But I recommend striving for simplicity and ease of implementation.

Agenda

1. Administrative

   • Small note on cleanup protocols: re-usable solder shouldn’t go in the waste bins. And let’s try to clean up detritus after using the soldering stations.

   • I’ve received just a couple of clearance documents. If you have them, please forward me scans of your PACA, PATCH, and FBI results. HR/Act 153 will not supply them to me directly, but I will need to give them to the museum.

2. Assignments

   • Due today: Demo 2: Single-bit Feedback

   • Due Mon Sep 23: Demo 3: The Conversation. This will be performed in pairs:

     1. Xiang, Griffin

     2. Quincy, Hagan

     3. Patricia, Sophia

     4. Halanna, Wenqing

     5. Katherine, Omisa

     6. Jai, Caio

     7. Julian, Tushhar

     8. Edward, Spencer

   • Due Mon Sep 23: read Investigating Rocks and Sand

3. In-class

   • Rapid-fire critique. This time, each person will show their work to the whole class from their table (we’ll all move around), then pose their own unresolved question. We’ll have time for just one or two observations each as feedback. Goal: three minutes per person.

   • review timer
     

   • Discussion of event-loop programming.

     • non-blocking.ino (below)

     • Exercise: Event-Loop Programming

     • EventBusyBox Arduino Sketch

     • MusicSequenceDemo Arduino Sketch

     • PinballGame Arduino Sketch

     
     

   • Brief discussion of state machines.

     • Exercise: Input Hysteresis

     
     

   • Brief pair meetings to start thinking about ‘conversation’ ideas and sharing contact information.

Lecture code samples

(See also Lecture Sample Code).

// 1. Blink the onboard Arduino LED on pin 13.
// 2. Demonstrate a non-blocking event loop.
// 3. Demonstrate micros() and timing calculations.
// 4. Note the absence of delay().  For comparison, see blink.ino.

void setup(void)
{
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop(void)
{
  static unsigned long last_update_clock = 0;

  unsigned long now = micros();
  unsigned long interval = now - last_update_clock;
  last_update_clock = now;

  static long led_blink_timer = 0;
  static bool led_blink_state = false;
  const long led_blink_interval = 500000;
 
  led_blink_timer -= interval;
  if (led_blink_timer <= 0) {
    led_blink_timer += led_blink_interval;

    led_blink_state = !led_blink_state;
    digitalWrite(LED_BUILTIN, led_blink_state);
  }
}