//Stimulator version 2.0  
/*
Pulse train:
1-255 pulses
0-4 sec pulse duration
0-4 sec pulse spacing
0-4 sec train repeat time 
0-30 volt amplitude
 
Pulse output is port D.3
Synch output is port D.4 
 
Trigger is either manual or periodic
Manual trigger is port D.2

timer 0 ISR generates pulse timing
timer 1 generates PWM for amplitude control on pin OC1A (D.5) 
  continuously so lowpass filter can average it
main loop handles parameter setting and rs232 comm
*/

#include < 90s8515.h> 
#include < Stdio.h>  
#include < delay.h> 
#include < stdlib.h>
#include < math.h>

#define begin {
#define end   }    
 
//input parameters
unsigned char num;      //number of pulses
unsigned int dur;       //pulse duration
unsigned long durL;     //holds duration string for float convert
unsigned int delay;     //pulse spacing 
unsigned long delayL;   //holds delay string
unsigned int rep;       //pulse train repeat time 
unsigned long repL;     //holds repeat time string   
unsigned int amp;       //pulse amplitude 0-255 

//state variables 
unsigned int elapsedT;  //running stimulus time
unsigned int nextT;     //next event time
unsigned char mode;     //manual or repeat  'm' or 'r'
unsigned char pulseon;  //state machine variable 1 or 0
unsigned char currentpulse;//current pulse num
unsigned char starting; //indicates first time thru ISR
unsigned char cmd;      //serial command character

float Conversion;       //converts mSec to units of 64 microSec

//#pragma savereg-
//********************************************
//timer 0 overflow ISR
interrupt [TIM0_OVF] void t0_overflow(void)
begin

   //check for starting and emit synch pulse, reset time
   if (starting)
   begin  
      PORTD.4 = 1;      //start synch pulse output
      starting = 0;     //on next ISR we won't be starting
      elapsedT = 0;     //relative to pulse train start
      pulseon = 0;      //starts in the off state 
      nextT = delay;    //next deadline time    
      currentpulse = 0; //the pulse number
      PORTD.4 = 0;      //end synch pulse     
   end
     
   else  //not starting
   begin   
      elapsedT++;       //all times are in 't0 ovfl tick units'
         
      //at end of pulse train: 
      //check for manual mode and kill timer  
      //otherwise set starting back to 1 for next train
      if (elapsedT == rep)
      begin 
         PORTD.3 == 0;          //kill the output pulse just in case
         if (mode == 'r')
            starting=1;         //get ready to restart
         if (mode == 'm')
            TCCR0=0;            //kill this ISR 
      end
      
      else if (elapsedT == nextT)
      begin 
         //have we putput all of the pulses?
         if (currentpulse < num)
         begin
            if (pulseon)
            begin       //turn off the pulse
               pulseon = 0; 
               PORTD.3 = 0; 
               nextT = elapsedT + delay;
            end
            else
            begin       //turn on the pulse
               pulseon = 1;  
               PORTD.3 = 1;
               currentpulse++; //inc the pulse cout
               nextT = elapsedT + dur;
            end //pulseon else   
         end
      
         else   //(currentpulse==num) so the train is done
         begin 
            PORTD.3 = 0; //kill the last pulse   
            nextT = 0;  //impossible time marker so next match is rep   
         end  
         
      end //if elapsedT 
      
   end //else not starting

end  //ISR
        
//
//********************************************* 
//#pragma savereg+

void main(void)
begin 
  
  //serial comm setup (no interrupts)
  UCR = 0x18 ;
  UBRR = 51; //25 ;   4 MHz value
  //putsf("\rStimulator 2.0 copyright Cornell University\r"); 
    
  //timer 0 setup
  TIMSK = 0x02 ;        //Timer 0 ovfl enable
  TCCR0 = 0;            //Timer 0 is off 
  
  //timer 1 setup (rest of setup is in ISR)
  TCCR1B = 0;           //Timer 1 is off
  
  //port D setup  
  DDRD.2 = 0 ;          //port D.2 is trigger input 
  PORTD.2 = 1;          //turn on D.2 internal pullup
  DDRD.5 = 1 ;          //port D.5 is PWM output 
  DDRD.3 = 1;           //port D.3 is main pulse
  DDRD.4 = 1;           //port D.4 is synch pulse
    
  //Convert 10*mSec to units of 64 microSec
  //                            32
  Conversion = 1000.0/32.0/10 ; // 1000.0/64.0/10 ;
  
  //turn on all interrupts
  #asm 
    sei
  #endasm 
  
  /*main event loop 
  two events:
    serial command input
    --s stop
    --g go
    --p set parameters  number,amplitude,dur,delay,rep
    --m set mode manual/repeat
    starting pushbutton in manual mode
  */ 
  while(1)
  begin     
    //if manual, check button D.2 for a trigger (active-low)
     if (mode=='m' && PIND.2==0)
     begin    
        TCNT0=0;
        TCCR0=1;
        starting=1; 
        //debounce the switch and wait for release
        delay_ms(50);  
        while(PIND.2==0){};
        delay_ms(50);
      end  //pushbutton event  
      
    //check USR for a valid character and get it
    if (USR.7==1)
    begin          
       cmd=getchar();
       switch (cmd)
       begin   
          case 's':
             //to stop, terminate timer ISR and kill any output
             TCCR0 = 0;  //turn off timer 0
             PORTD.3 = 0;  //and kill any leftover pulse        
             break;
          case 'g':
             if (mode=='r') 
             begin
                TCNT0=0;        //zero the clock
                TCCR0=1;        //and start it  
                starting=1;     //flag to tell ISR to start new pulse train
             end
             //putsf("running\r");
             break;
          case 'p':
             //putsf("\r\n#, amp, dur, delay, rep\r") ;
             scanf("%d%d%d%d%d", &num, &, &durL, &delayL, &repL) ; 
             //printf("%d%d%d%d%d\r\n", num,amp,durL,delayL,repL) ;
            //convert time units
            dur = floor(durL*Conversion+0.5);
            delay = floor(delayL*Conversion+0.5);
            rep = floor(repL*Conversion);  
            OCR1A = 256-amp;     //loads PWM duty cycle 
            TCCR1B = 1;         //turn on PWM
            TCCR1A = 0xc1;      //8-bit, inverted PWM mode
            TCNT1 = 0;          //start at zero to set phase 
            break;      
          case 'm':    
             mode=getchar();
             break; 
          case 'r':
             mode=getchar();
             break;           
       end //switch              
    end  //if (USR==1) serial event handler     
  end //while(1)  
end //main