MikroElektronika books

Example 6 – Realization of pulse width modulation

The example shows the realization of continuously varying pulse width modulation (PWM). The continously modulated output is on the PORTE.0 pin which is monitored by a LED diode. The realization is carried out by using the mikroPascal compiler for dsPIC30F microcontrollers. Fig. 13-6 shows the electric diagram of the realized continuous PWM of a LED diode connected to PORTE.0.

pic-microcontrollers-programming-dspic-in-pascal-chapter-13-image-6

Fig. 13-6 The electric diagram of the realized continuous PWM of a LED diode connected to PORTE.0.

program PWM;

var i, duty_50 : word;

begin
  ADPCFG := 0xFFFF;
  TRISE  := 0;
  PORTB  := 0xAAAA;
  TRISB  := 0;
  Delay_ms(1000);

  duty_50 := Pwm_Mc_Init(5000,1,0x01,0);           // Pwm_Mc_Init returns 50% of the duty
  i := duty_50;
  Pwm_Mc_Set_Duty(i, 1);
  Pwm_Mc_Start();

  repeat
    begin
      i := i - 1;
      Pwm_Mc_Set_Duty(i,1);
      Delay_ms(1);
      if (i = 0) then
        i := duty_50 * 2 - 1;                // Do not allow the overflow
      PORTB := i;
    end;
  until false;
end.