/*
The program sets the duty cycle of a 20,000Hz PWM signal based on either an A/D
value or and external PWM signal

Modes

Pot Control
Every 262ms it samples the A/D value and set the duty percentage based on the full
scale percentage of the A/D value

PWM
It monitors the duty cycle of a relatively slow PWM signal of 200Hz.
to a resolution of at least 100 and sets a higher 20,000Hz PWM with the same duty
cycle.  It should set the duty cycle correctly at the start of the second full 
period of the monitored PWM.


Author: B. Dring
Date: 8/19/2009
Revision: 0.3
Status: Basic Testing Complete
Hardware: PIC16F877A
Clock: 8,00,000 MHz (20,000,000 would be better...need a crystal) 
Compiler:  CCS PCWH 4.042
URL:  www.eng-serve.com   www.buildlog.net

===============================================================================

Using: #int_TIMER2
The watched PWM signal has a period of .005 seconds (1/200Hz).  We want a 
resolution of at least 100 so that requires a sample rate of 50us.  
We will use Timer2 to do this.  Each Timer2 interupt will increment 
pwmPeriodCounter and, if the pin is high, pwmOnTimeCounter .

================================================================================

Using: #int_EXT
An external interrupt triggers on the rising edge of the PWM.  Each interrupt will 
determine the duty cycle of the external PWM signal, set the internal PWM
duty cycle and reset the counters.  

A flag will also be set to show we got a pulse and the timer 0 will be reset


ext_int_edge( L_TO_H );

================================================================================
#int_TIMER0
If the PWM goes away we need to set the duty cycle to 0.
Reset the two counters and set the duty cycle to 0

===============================================================================



*/


#include "C:\prouser\laser_misumi\PIC_PWM\laser_pwm3.h"


#include   // LCD Driver for EasyPIC4 board

#define MAX_PWM_DUTY 100
#define MAX_ADV_VALUE 255

#define CONTROL_MODE_OFF            0
#define CONTROL_MODE_POT            1
#define CONTROL_MODE_EXTERNAL_PWM   2

#define CONTROL_MODE_SW_PIN          PIN_B7
#define EXTERNAL_INTERRUPT_PIN       PIN_B0

unsigned int32 pwmOnTimeCounter;
unsigned int32 pwmPeriodCounter;
unsigned int8 dutyCycle;
short bGotPwmPulse;
int8 controlMode;


unsigned int16 adValue;

// sets PWM to zero duty
void zero_pwm()
{
   pwmOnTimeCounter = 0;
   pwmPeriodCounter = 0;
   dutyCycle = 0;
   set_pwm1_duty(dutyCycle);
}

// this occurs on the rising edge of eash PWM
#int_EXT
void  EXT_isr(void)
{

   if (controlMode == CONTROL_MODE_EXTERNAL_PWM)
   {
      // this tells the interrupt watching PWM to stop that it is still going
      bGotPwmPulse = true;
      set_timer0(0);
      
      
      // determine the duty cycle
      if (pwmPeriodCounter !=0) // prevent divide by zero
      {
         dutyCycle = pwmOnTimeCounter * MAX_PWM_DUTY / pwmPeriodCounter;
      }
      
      set_pwm1_duty(dutyCycle);
      
      // reset the counters
      pwmOnTimeCounter = 0;
      pwmPeriodCounter = 0;
   }   
}

#int_TIMER0   // used to determine if PWM has stopped
void  TIMER0_isr(void) 
{

   if (controlMode == CONTROL_MODE_EXTERNAL_PWM)
   {

      if (!bGotPwmPulse)
      {
         zero_pwm();
        
      }
      bGotPwmPulse = false;
   
   }
}

#int_TIMER1   // for periodic update of POT value, LCD and LED heartbeat
void  TIMER1_isr(void) 
{
   output_toggle(PIN_B1);
   
   if (controlMode == CONTROL_MODE_POT)
   {
      adValue = read_adc();      
      dutyCycle = adValue * MAX_PWM_DUTY / MAX_ADV_VALUE;  
      set_pwm1_duty(dutyCycle);
   
   }   
   
   printf(lcd_putc,"\fDuty: %u",dutyCycle);
   
   
}

#int_TIMER2
void  TIMER2_isr(void) 
{


   // this timer fires every 50us.  It is used to determine the duty cycle 
   
   if (controlMode == CONTROL_MODE_EXTERNAL_PWM)
   {
   
   
      if (input(EXTERNAL_INTERRUPT_PIN))
      {
         pwmOnTimeCounter++;
      }
      pwmPeriodCounter++;
   }
}

void main()
{

   setup_adc_ports(AN0);
   setup_adc(ADC_CLOCK_INTERNAL);
   
   setup_psp(PSP_DISABLED);
   setup_spi(SPI_SS_DISABLED);
   
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_64); // 8ms
   setup_timer_1(T1_INTERNAL|T1_DIV_BY_8); // 262ms
   setup_timer_2(T2_DIV_BY_1,99,1);  //50uS
   
   setup_vref(FALSE);
   
   setup_ccp1(CCP_PWM);      
   
   ext_int_edge( L_TO_H );
   
   
   enable_interrupts(INT_EXT);  // B0 on PIC16F877A
   enable_interrupts(INT_TIMER0);
   enable_interrupts(INT_TIMER1);
   enable_interrupts(INT_TIMER2);
   
   dutyCycle = 0;
   
   set_pwm1_duty(dutyCycle);
   
   
   //setup_comparator(NC_NC_NC_NC);
   setup_vref(FALSE);
   

   // TODO: USER CODE!!
   
   set_adc_channel(0);


   
   lcd_init();
   lcd_putc("\fReady...\n");
   
   // manually select the mode...TO DO add switched control
   controlMode = CONTROL_MODE_EXTERNAL_PWM;
   //controlMode = CONTROL_MODE_POT;
   
   switch(controlMode)
   {
      case CONTROL_MODE_POT:
         lcd_putc("Pot Mode");
      break;
   
      case CONTROL_MODE_EXTERNAL_PWM:
         lcd_putc("Ext PWM Mode");
      break;
   
   }
   
   delay_ms(1500);
   
   
   enable_interrupts(GLOBAL);
   
   
   while(true)
   {
      // nothing to do here...
      // to do: turn on the watchdog and reset it in the main loop
   }

}