simple PWM – DSPIC30F2010

100KHz AND 200KHz SQUARE WAVE USING DSPIC

PROGRAM

program BLINK
dim current_duty, current_duty1, pwm_period1 , pwm_period2 as word
main:
  PORTD = 0                ' set PORTD to 0
  TRISD = 0                ' designate PORTD pins as output
  current_duty   = 20      ' initial value for current_duty
  current_duty1 = 10       ' initial value for current_duty1
  pwm_period1 = PWM_Init(100000 , 1, 1, 2)   'frequency ,channel no.,timer prescale value(1, 8, 64, and 256 ) ,timer no (2 or 3)
  pwm_period2 = PWM_Init(200000, 2, 1, 3)    'frequency ,channel no.,timer prescale value(1, 8, 64, and 256 ) ,timer no (2 or 3)
  PWM_Start(1)
  PWM_Start(2)
  PWM_Set_Duty(current_duty,   1)   ' Set current duty for PWM1
  PWM_Set_Duty(current_duty1, 2)   ' Set current duty for PWM2   'OC2RS=50---duty cycle actuall writes to this register
  while (TRUE)                     ' endless loop
  wend
end.

HOW TO CALCULATE PWM DUTY CYCLE

• PWM duty ratio depend on output frequency
• 16MHz crystal as clock source
• PRESCALE VALUE ARE 1, 8, 64, and 256

Maximum duty ratio = F_OSC/(F_OUTPUT*4*PRESCALE VALUE) – 1

FOR 100KHz

Maximum duty ratio = 16MHz / (100KHz *4 *1) – 1 = 39

FOR 200KHz

Maximum duty ratio = 16MHz / (200KHz *4 *1) – 1 = 19

I HAVE USED 50% DUTY RATIO FOR BOTH

800KHz SQUARE WAVE USING DSPIC

PROGRAM

program BLINK
dim current_duty, current_duty1, pwm_period1 , pwm_period2 as word
main:
  PORTD = 0                ' set PORTD to 0
  TRISD = 0                ' designate PORTD pins as output
  current_duty   = 20      ' initial value for current_duty
  current_duty1 = 2        ' initial value for current_duty1
  pwm_period1 = PWM_Init(100000 , 1, 1, 2)   'frequency ,channel no.,timer prescale value(1, 8, 64, and 256 ) ,timer no (2 or 3)
  pwm_period2 = PWM_Init(800000, 2, 1, 3)    'frequency ,channel no.,timer prescale value(1, 8, 64, and 256 ) ,timer no (2 or 3)
  PWM_Start(1)
  PWM_Start(2)
  PWM_Set_Duty(current_duty,   1)   ' Set current duty for PWM1
  PWM_Set_Duty(current_duty1, 2)   ' Set current duty for PWM2   'OC2RS=50---duty cycle actuall writes to this register
  while (TRUE)                     ' endless loop
  wend
end.