/********************************************************************************
 * MAHE, 13.05.2002, 12H40 - now compiling as project of separated source files
 ********************************************************************************/
#include "pwm.h"
extern unsigned char errorno;
/********************************************************************************************
 * Init of PWM channels
 * Init for PWM mode of Capcom module, p. 61
 * PR2's value is calculated like that:
 * We need a frequency of at least 15kHz, to
 * avoid hearing the motors. That gives us a
 * period Tpwm of 6,67,e-5, the formula is on
 * p. 61 of the PIC16F877 documentation.
 * With TMR2 prescaler set to 1 it is necessary
 * to set PR2 to decimal 65=0x41.
 * Duty cycle, 10 bits:
 * 00 0000 0000b = 0d
 * 00 1111 1111b = 255d = 1/4 = default
 * 01 1111 1111b = 511d = 1/2
 * 10 1111 1111b = 767d = 3/4
 * 11 1111 1111b = 1023d
 * 8 MSB Bits in CCPR1L or CCPR2L:
 * 0011 1111 = 0x3F
 * 1011 1111 = 0xBF
 * PWM Mode for Capcom module is initialised 
 * by setting CCP1CON and CCP2CON file bits
 * 3:0 to binary 11XX.
 ********************************************************************************************/
void initPWM(void) {
  /**************
   * Setup PR2
   **************/
  PR2=0x41;
  /****************************************
   * Set duty cycle 8 MSB Bits to 0, do not
   * forget the 2 LSB later !
   ****************************************/
  CCPR1L=0x00;
  CCPR2L=0x00;
  /**************************************************
   * make RC2/CCP1 and RC1/CCP2 pins an output, p. 29
   * by clearing the pins
   **************************************************/
  PORTC=0x00;
  TRISC&=0xF9;    /* 1111 1001 */
  /******************************************************************
   * set Timer 2 TMR2 prescale value to 1 by clearing bits 1:0, p. 55
   * and start the timer by setting bit 2
   * 0000 0100=0x04
   ******************************************************************/
  T2CON=0x04;
  /***********************************************************
   * setup CCP1,CCP2 for PWM operation
   * clear 2 LSB bits 5:4, set bits 3:0 
   * to 1100 for PWM mode
   * 0000 1100=0x0C
   * 0x00 to clear the two LSB bits of the PWM duty cycle
   * 0x30 to set the two LSB bits of the PWM duty cycle
   * 0x0C to set PWM operation of CCP1, CCP2 module
   ***********************************************************/
  CCP1CON=0x0C;
  CCP2CON=0x0C;
  /*************************************************
   * Both CCP1 and CCP2 should now be configured for
   * PWM operation, but the duty cycle is still set
   * to 0, so no signal should appear.
   *************************************************/
}
/********************************************************************************************
 * PWMChanEN
 * Sets or Resets the enable for PWM channel 0 or 1
 ********************************************************************************************/
void PWMChanEN(char channel, char state) {
  /*************************
   * check parameters, this is
   * why I like objects .....
   *************************/
  if(channel > 1 || channel < 0 || state > 1 || state < 0 ) {
    /***************
     * scream error
     ***************/
    errorno=ERR_PWMCHANNELNO; 
  }
	 
  if(channel==0) {
    /**********
     * chan0
     **********/
#ifdef PWMCHAN0_INVERTED    
    state=!state;
#endif
    PWM0ENABLE=state;
  } else {
    /**********
     * chan1
     **********/
#ifdef PWMCHAN1_INVERTED    
    state=!state;
#endif
    PWM1ENABLE=state;
  }
}
/********************************************************************************************
 * Sets value of Duty Cycle for PWM channel 0 or 1
 ********************************************************************************************/
void setDutyCycle( const unsigned char chan, unsigned char MSB, unsigned char LSB ) {
  volatile char *pDutyCycleMSB;
  volatile char *pDutyCycleLSB;
  /**********************
   * Check parameters
   **********************/
  if(chan<0 || chan > 1) {
    errorno=ERR_PWMCHANNELNO;
  }

  /*********************
   * Change pointers to
   * the correct register
   *********************/
  if(chan==1) {
#ifdef PWMCHAN1_INVERTED    
    PWMIN12=1;
#endif
    pDutyCycleMSB=&CCPR1L;
    pDutyCycleLSB=&CCP1CON;
  } else {
    /*************
     * Channel 0
     *************/
#ifdef PWMCHAN0_INVERTED    
    PWMIN02=1;
#endif
    pDutyCycleMSB=&CCPR2L;
    pDutyCycleLSB=&CCP2CON;
  }

  /**************
   * MSB is easy,
   * just assign it
   **************/
  *pDutyCycleMSB=MSB;

  /***********************
   * PWM 2 LSB bits are stored
   * in CCPxCON<5:4>
   * if 2 LSB bits in LSB are
   * set:
   * LSB:  0000 0011
   * CCPxCON: nn11 nnnn  n->don't change
   * First clear the bits 5:4
   * in CCPxCON. Then set to 
   * result in LSB
   ***************************/
  LSB&=0x03; /* 0000 0011 */
  LSB=LSB<<4;
  (*pDutyCycleLSB)&=0xCF;  /* 1100 1111 */
  (*pDutyCycleLSB)|=LSB;
}