View source for Vector Clock

==Synopsis==
Use an oscilloscope in XY mode to display time.  Uses two MCP4725 and a DS1302.
==Notes==
Known bug.  12 hour hand is missing.  Hour hand does not creep, but instead moves in one hour notches.  Ideally, use the Sine function to determine precise positioning.
==Code==
<syntaxhighlight lang="C++" line='line'>
//Arduino UNO
//Pin 5  : DS1302 Chip Enable 
//Pin 6  : DS1302 Data
//Pin 7  : DS1302 Data Clock
//Pin A4 : MCP4725 SDA pins
//Pin A5 : MCP4725 SCK pins
//
//5 Volt pin powers all external devices
//Please verify that your modules are also
//compatible with a 5 volt supply.
//
//On the MCP4725 devices, attach one A0
//pin to 5 volts and the other to ground
//to ensure these are on different addresses
//The SDA and SCK pins on these can be attached
//to each other.  The device ID of the
//MCP4725 had to be discovered experimentally
//and you may need to discover those values as
//well.
//
//On the MCP4725, choose the voltage out pins
//to be connected to the X and Y inputs of
//your oscilloscope such that the clock is suitably rotated.

#include <Wire.h>
#include <Adafruit_MCP4725.h>
#include <DS1302.h>

//Begin DS1302 Configuration
const int kCePin  = 5;  // Chip Enable
const int kIoPin   = 6;  // Input/Output
const int kSclkPin = 7;  // Serial Clock
DS1302 rtc(kCePin, kIoPin, kSclkPin);
//End DS1302 Configuration

// Begin MCP4725 Configuration
Adafruit_MCP4725 dac_X;
Adafruit_MCP4725 dac_Y;
// End MCP4725 Configuration

//timing and counnters
long us;
bool toggle;
byte t=0;

const uint16_t DACLookup_FullSine_8Bit[256] =
{
  2048, 2098, 2148, 2198, 2248, 2298, 2348, 2398,
  2447, 2496, 2545, 2594, 2642, 2690, 2737, 2784,
  2831, 2877, 2923, 2968, 3013, 3057, 3100, 3143,
  3185, 3226, 3267, 3307, 3346, 3385, 3423, 3459,
  3495, 3530, 3565, 3598, 3630, 3662, 3692, 3722,
  3750, 3777, 3804, 3829, 3853, 3876, 3898, 3919,
  3939, 3958, 3975, 3992, 4007, 4021, 4034, 4045,
  4056, 4065, 4073, 4080, 4085, 4089, 4093, 4094,
  4095, 4094, 4093, 4089, 4085, 4080, 4073, 4065,
  4056, 4045, 4034, 4021, 4007, 3992, 3975, 3958,
  3939, 3919, 3898, 3876, 3853, 3829, 3804, 3777,
  3750, 3722, 3692, 3662, 3630, 3598, 3565, 3530,
  3495, 3459, 3423, 3385, 3346, 3307, 3267, 3226,
  3185, 3143, 3100, 3057, 3013, 2968, 2923, 2877,
  2831, 2784, 2737, 2690, 2642, 2594, 2545, 2496,
  2447, 2398, 2348, 2298, 2248, 2198, 2148, 2098,
  2048, 1997, 1947, 1897, 1847, 1797, 1747, 1697,
  1648, 1599, 1550, 1501, 1453, 1405, 1358, 1311,
  1264, 1218, 1172, 1127, 1082, 1038,  995,  952,
   910,  869,  828,  788,  749,  710,  672,  636,
   600,  565,  530,  497,  465,  433,  403,  373,
   345,  318,  291,  266,  242,  219,  197,  176,
   156,  137,  120,  103,   88,   74,   61,   50,
    39,   30,   22,   15,   10,    6,    2,    1,
     0,    1,    2,    6,   10,   15,   22,   30,
    39,   50,   61,   74,   88,  103,  120,  137,
   156,  176,  197,  219,  242,  266,  291,  318,
   345,  373,  403,  433,  465,  497,  530,  565,
   600,  636,  672,  710,  749,  788,  828,  869,
   910,  952,  995, 1038, 1082, 1127, 1172, 1218,
  1264, 1311, 1358, 1405, 1453, 1501, 1550, 1599,
  1648, 1697, 1747, 1797, 1847, 1897, 1947, 1997
};

const long HandsX[60] = 
{
  2047, 2261, 2473, 2680, 2880, 3071, 3251, 3417,
  3569, 3704, 3820, 3918, 3994, 4050, 4083, 4095,
  4083, 4050, 3994, 3918, 3820, 3704, 3569, 3417,
  3251, 3071, 2880, 2680, 2473, 2261, 2048, 1834,
  1622, 1415, 1215, 1024,  844,  678,  526,  391,
   275,  177,  101,   45,   12,    1,   12,   45,
   101,  177,  275,  391,  526,  678,  844, 1024,
  1215, 1415, 1622, 1834
};
const long HandsY[60] =
{
  4095, 4083, 4050, 3994, 3918, 3820, 3704, 3569,
  3417, 3251, 3071, 2880, 2680, 2473, 2261, 2048,
  1834, 1622, 1415, 1215, 1024,  844,  678,  526,
   391,  275,  177,  101,   45,   12,    1,   12,
    45,  101,  177,  275,  391,  526,  678,  844,
  1024, 1215, 1415, 1622, 1834, 2047, 2261, 2473,
  2680, 2880, 3071, 3251, 3417, 3569, 3704, 3820,
  3918, 3994, 4050, 4083
};

void Hand(byte v, byte len)
{
  long i,x,y;
  for(i=0;i<len;i++)
  //Draw from center
  {
    //2048,2048 is the center.
    x=2048+(HandsX[v]-2048)*i/100; 
    y=2048+(HandsY[v]-2048)*i/100; 
    dac_X.setVoltage(x   , false,400000);
    dac_Y.setVoltage(y   , false,400000);
  }
}

void Circle()
{
    uint16_t i;
    uint16_t j;
      for (i = 0; i < 256; i++)
      {
        dac_X.setVoltage(DACLookup_FullSine_8Bit[i], false);

        j=i+193;
        j=j%256;
        dac_Y.setVoltage(DACLookup_FullSine_8Bit[j], false);
        
      }
}

void setup(void) {
  Serial.begin(9600);
  delay(1000);
  rtc.writeProtect(true);
  Serial.println("This page intentionally left blank.");

  dac_X.begin(0x63);
  dac_Y.begin(0x62);
  us = 500000 + micros();
}

void loop(void) 
{
  byte hr;
  Time tm;
  tm = rtc.time();
  hr=tm.hr;
  while(hr>12) hr -= 12;
  
   if(t==0)
  {
    //Update time from rtc

    t=1;
  }

  
  if(micros()<us)
  {
    Circle();
    Hand(tm.min,70);  //Minutes
    Hand(hr*5,50); //Hours
    if(toggle){Hand(tm.sec,90);} //Seconds
  }
  else
  {
      us = 500000 + micros();
      if(toggle) toggle=LOW; else toggle=HIGH;
      
      t++;  
  }
}
</syntaxhighlight>