// Chapter 12 6812 C programs
// Jonathan W. Valvano, 2/26/07
// This software accompanies the book,
// Embedded Microcomputer Systems: Real Time Interfacing, Second Edition
// published by Thomson Engineering, 2006




// table of multiple unsigned (x,y), piece-wise linear function
unsigned short const ADCtable[8]= { 0,  8, 50, 96,146,199,255,65535};
unsigned short const Ttable[8]= { 500,500,450,400,350,300,250,  250};
unsigned short LookUp(unsigned short data);
interrupt 11 void TOC3handler(void){ // TCNT is 4us
unsigned short Data;      // raw ADC result, 0 to 255
  Data = ADC_In(0x81);	  // 0 to 255
  Fifo_Put(LookUp(Data)); // 250 to 500 (0.1C)
  TC3 = TC3+25000;        // every 0.1s at 4 MHz 
  TFLG1 = 0x08;           // acknowledge OC3
}
//Program 12.2.  Real-time measurement of temperature.   




interrupt 11 void TOC3handler(void){    // 480Hz
static short sum=0,n=0; short data;
  data = (0x00FF&ADC_In(7))-128;        // real EKG
  sum += data;     // sum=x(n)+x(n-1)+x(n-2)+x(n-3)
  n++;
  if(n==4){
    n = 0; 
    Fifo_Put(sum/4);    // 120Hz 
    sum = 0;
  }
  TC3 = TC3+16667;      // 2083.375us = 479.99 Hz
  TFLG1 = 0x08;         // acknowledge OC3
}
//Program 12.3.  Real-time sampling of EKG.   


short Data;	  // ADC sample, -128 to +127, 8-bit signed ADC sample
short x[50];   // 60Hz notch-filtered EKG, 120Hz
short y[50];   // low pass filter, 120Hz
short z[50];   // high pass filter, 120Hz
short w[50];   // squared result, R-wave power, 120Hz
short Rwav;    // moving average of R-wave power, energy
unsigned short n=25;   // 25,26, ..., 49
unsigned short Trigger;
#define HIGH 100   // trigger when over this
#define LOW 20     // reset when under this
unsigned short Rcount;     // number of R-waves
unsigned short Rfirst;     // time of first R-wave
unsigned short Rlast;      // time of last R-wave
unsigned short HeartRate;  // units bpm
void main(void) { unsigned short time;	 // units 1/120sec
short lpfSum=0,hpfSum=0,RwavSum=0;
  LCD_Open(); LCD_OutString("EKG System - Valvano"); 
  Fifo_Init();
  ADC_Init();     // Activate ADC 
  Timer_Init();   // initialize 480Hz OC3 
  Trigger =0;     // looking for HIGH
  for(;;) {
    Rcount = 0;
    Rlast = 0;
    for(time=0;time<600;time++){  // 120 Hz, every 5 second
      while(Fifo_Get(&Data)){};   // Get data from background thread
      LCD_Plot(Data);             // draw voltage versus time plot
      n++; if(n==50) n=25;     
      x[n] = x[n-25] = Data;           // new data
      lpfSum  = lpfSum+x[n]-x[n-4];
      y[n] = y[n-25] = lpfSum/4;       // Low Pass Filter
      hpfSum  = hpfSum+y[n]-y[n-10];
      z[n] = z[n-25] = y[n]-hpfSum/10; // High Pass Filter
      w[n] = w[n-25] = (z[n]*z[n])/10; // Power calculation
      RwavSum = RwavSum+w[n]-w[n-24];  // 200ms wide moving average
      Rwav = RwavSum/24;
      if(Trigger){
        if(Rpow<LOW){
          Trigger = 0;      // found low
        }
      } else{
        if((Rpow>HIGH)&&((time-Rlast)>30)){ // max HR= 240bpm
          Trigger = 1;     // found high
          if(Rcount){
            Rlast = time;  // mark time of last R-wave, units 1/120sec
          } else{
            Rfirst = time; // mark time of first R-wave
          }
          Rcount++;
        }
      }
    }
    if(Rcount>=2){
      HeartRate = (7200*(long)(Rcount-1))/(long)(Rlast-Rfirst);
    } else{
      HeartRate = 0;
    }
    LCD_OutUDec(HeartRate);  // display results
  } 
}
//Program 12.4.  Measurement of heart rate.