pwmfullbridge.c

pulse width modulation pwm of multilevel inverter

#define     XTFREQ   7372800UL          // On-board Crystal freq
#define     PLLMODE  16                 // On-chip PLL setting
#define     Fosc     (XTFREQ*PLLMODE)   // Freq of oscillator = 117,964,800 Hz
#define     FCY      (Fosc/4)           // Instruction Cycle Freq = 29,491,200 Hz, TCY = 33.9 nsec

#include <p30Fxxxx.h>

#define FHz2Tus(FHZ) (1.0e6/FHZ)       // convert freq Hz to period usec
const double TCY     = FHz2Tus(FCY);   // processor instruction period, usec

#define      FPWM                     160000          // PWM frequency, Hz
const float  TPWM                   = FHz2Tus(FPWM);  // PWM period 

int pwmPTPER;
int pwmPDC;  // PDC, Pulse Duty Cycle

int main(void)
{
  LATE  = 0x0;                // PWM pins low
  TRISE = 0b1111111111000000; // PWM RE0-5=PWM1L,...,PWM3H RE8=~FLTA<-also INT0

  /*~~~~~~~~~~~~~~~~~~~~~~~ PWM Configuration ~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ 
  const int   PRESCALE   = 1;
     
  PTCON   = 0;
  PTCONbits.PTOPS  = 0; // output post scale 1:1 = 0
  PTCONbits.PTCKPS = 0; // time base clock pre scale 1:1,1:4,1:16,1:64 = 0,1,2,3
  PTCONbits.PTMOD  = 0; // free run=0, single-event=1, up-down=2, up-down-interrupts=3
     
  PWMCON1 = 0;
  PWMCON1bits.PMOD1     = 0;  // output mode: 0=complementary, 1=independent
  PWMCON1bits.PMOD2     = 0;  // output mode: 0=complementary, 1=independent
  PWMCON1bits.PMOD2     = 0;  // output mode: 0=complementary, 1=independent
  
  PWMCON1bits.PEN1L     = 1;  // PWM1L is controlled by PWM module RE0=pin 26
  PWMCON1bits.PEN1H     = 1;  // PWM1H is controlled by PWM module RE1=pin 25
  PWMCON1bits.PEN2L     = 1;  // PWM2L is controlled by PWM module RE2=pin 24
  PWMCON1bits.PEN2H     = 1;  // PWM2H is controlled by PWM module RE3=pin 23
  
  PWMCON1bits.PEN3L     = 0;  // PWM3 not used, RE4=pin 22 digital I/O
  PWMCON1bits.PEN3H     = 0;  // PWM3 not used, RE5=pin 21 digital I/O
  
  
  // OVDCON = 0;            // clearing OVDCON kills PWM output

  PWMCON2 = 0; 
  SEVTCMP = 0;               // special event compare
  
  PTMRbits.PTMR = 0;

  #define CALC_PTPER_FREE_RUN(scale,freqHz) ((scale * FHz2Tus(freqHz)) / TCY - 1. + 0.5)
  #define CALC_PTPER_UP_DOWN(scale,freqHz)  ((scale * FHz2Tus(freqHz) - 0.75)  /  (2. * TCY) + 0.5)
  #define CALC_PTPER(scale,freqHz) CALC_PTPER_FREE_RUN(scale,freqHz) // using free run
//#define CALC_PTPER(scale,freqHz) CALC_PTPER_UP_DOWN(scale,freqHz)  // using up-down
 
  pwmPTPER = CALC_PTPER(PRESCALE,FPWM);
  PTPER = pwmPTPER;

  // 100% duty cycle is actually 50% since we are generating AC via the H-bridge
  pwmPDC  = 2*pwmPTPER;    // scope measures   50% duty cycle on PWM[12]H, DTCON1 = 0
  PDC1    = pwmPDC;
  PDC2    = 0;
  PDC3    = 0;
  
  DTCON1 = 0;             // dead time: eg if 10, 10 TCY = 10 * 33.9 nsec = 339 nsec
  
  IFS2bits.PWMIF = 0;     // interrupt off, if already active
  IEC2bits.PWMIE = 1;     // enable interrupt
  PTCONbits.PTEN = 1;     // Enable PWM Module  
  
  while(1)
    ;
}

void __attribute__((__interrupt__, no_auto_psv)) _PWMInterrupt(void)
{
   static int bToggle = 0;
   IFS2bits.PWMIF = 0;
   if(bToggle) {
     PDC1  = 0;
     PDC2  = pwmPDC;
     #if 0
     // enabling and disabling PEN1+PEN2 did not produce full wave H-bridge
     PWMCON1bits.PEN1H     = 0;
     PWMCON1bits.PEN1L     = 0;
     PWMCON1bits.PEN2H     = 1;
     PWMCON1bits.PEN2L     = 1; 
     #endif
   } else {
     PDC1  = pwmPDC;
     PDC2  = 0;
     #if 0
     // enabling and disabling PEN1+PEN2 did not produce full wave H-bridge
     PWMCON1bits.PEN1H     = 1;
     PWMCON1bits.PEN1L     = 1;
     PWMCON1bits.PEN2H     = 0;
     PWMCON1bits.PEN2L     = 0;
     #endif
   }
   bToggle = !bToggle;  
} 

/* vim: set cin et ts=2 sw=2 cino=>1s,e0,n0,f0,{0,}0,^0,\:1s,=0,g1s,h0,t0,+1s,c3,(0,u0 : */