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• We Do What We Must

  deʃhipu • 09/05/2015 at 10:16 • 0 comments

  Because we can. I had a 7-segment display left over from the #Talk Ranking Machine, and this really begged to be done. Yes, it's useless, silly, and potentially even dangerous if someone left it in a public place. But it was quite fun to do too.

  Both the display and the battery holder are soldered directly to the Pro Mini -- the pinout just happens to match. There is no off switch, you just have to remove the battery. The code looks like this:

  const int GND_PINS[] = {8, 12, 13, A2};
  const int VCC_PINS[] = {A1, 11, 6, 4, 3, A0, 7, 5};
  const unsigned char DIGITS[] = {
      0b00111111,
      0b00000110,
      0b01011011,
      0b01001111,
      0b01100110,
      0b01101101,
      0b01111101,
      0b00000111,
      0b01111111,
      0b01101111,
  };
  const int BEEP_PIN = 2;
  
  
  void show7seg(int number) {
      unsigned char digit;
      div_t result;
  
      for (int d = 0; d < 4; ++d) {
          result = div(number, 10);
          digit = DIGITS[result.rem % 10];
          number = result.quot;
          for (int s = 0; s < 8; ++s) {
              digitalWrite(VCC_PINS[s], digit & (1 << s));
          }
          pinMode(GND_PINS[d], OUTPUT);
          digitalWrite(GND_PINS[d], LOW);
          delay(2);
          pinMode(GND_PINS[d], INPUT);
      }
  }
  
  
  
  void setup() {
      for (int s = 0; s < 8; ++s) {
          pinMode(VCC_PINS[s], OUTPUT);
      }
      for (int d = 0; d < 4; ++d) {
          pinMode(GND_PINS[d], INPUT);
      }
      pinMode(9, OUTPUT);
      digitalWrite(9, LOW);
      pinMode(10, OUTPUT);
      digitalWrite(10, HIGH);
  }
  
  
  void loop() {
      static long int last = 0;
      static int count = 2400;
      long int now = millis();
  
      if (now - last > 500) {
          digitalWrite(10, LOW);
      }
      if (now - last > 1000) {
          count -= 1;
          if (count % 100 == 99) {
              count -= 40;
          }
          last = now;
          tone(BEEP_PIN, 1200, 25);
          digitalWrite(10, HIGH);
      }
  
      show7seg(count);
  }

  And that's pretty much it. I might actually make it a game, by adding several wires that you have to cut, that would either stop the counter or make it go faster or something...

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