My 0.015 minutes of fame on CNN

I recently wound up on CNN for a couple seconds doing some Arduino hacking as part of a segment on Google's workshops. Click the image for the full video. If you don't want to watch the whole thing, I appear at 1:00 and 1:39.

Ken Shirriff on CNN

For those who want technical details, I hacked together the following quick sketch to generate the interesting patterns you can see on the oscilloscope:

void setup()
{
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
}

int state = 1;
int count1 = 0;
int state2 = 1;
int count12 = 0;
int max1 = 20;
int max2 = 200;
int t = 0;

void loop() {

  if (count1-- <= 0) {
    state = 1-state;
    digitalWrite(5, state);
    count1 = max1;
  }
  if (count12-- <= 0) {
    state2 = 1-state2;
    digitalWrite(4, state2);
    count12 = max2;

    if (t++ > 20000) {
      max2 -= 1;
      if (max2 < 1) {
        max2 = 500;
      }   
      t = 0;
    }
  }
}
This sketch manually generates two square wave output with periods determined by max1 and max2. The frequency of the second varies occasionally (controlled by the loop with t). I used simple R-C filters on the outputs to turn the square waves into roughly triangular waves, and then fed this into the X and Y inputs of the oscilloscope. The result was constantly-varying Lissajou-like patterns.

I should point out the outputs generated this way are rather unstable because many thing can interrupt the timing loop. The above code is provided just in case your are curious. I don't recommend using this approach for anything real; using the PWM timers would yield much cleaner results.

Anyone have other ideas for easy ways to generate cool oscilloscope patterns with an Arduino?

2 comments:

  1. Hi Ken, your'e wrong, you weren't on CNN once, I saw you twice!

    Just wanted to say I enjoy your blog, and thanks for the effort. :)

    I found you when I was in a dark place with IR, your post really helped me, thanks again.

    ReplyDelete
  2. You are pretty :-)

    ReplyDelete