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PWM

 
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pandi_bece



Joined: 07 Sep 2007
Posts: 3

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PWM
PostPosted: Wed Oct 10, 2007 6:07 am     Reply with quote
hi...

how to gentrate the PWM frequency 0.1Hz to 300Hz with variable DUTYCYCLES..

i am using PIC16F877A .. osc freq 20MHz..CCP1(for PWM output pin).
tom_hanks



Joined: 04 Apr 2007
Posts: 20

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PostPosted: Wed Oct 10, 2007 8:37 am     Reply with quote
void pwmTask(unsigned int pulse_width,unsigned int period)
{
unsigned int time_on = pulse_width;
unsigned int time_off = period - pulse_width;
while(1)
{
pwm_output = 1; //pwm_output = signal connected to FET
sleep(time_on);
pwm_output = 0;
sleep(time_off);
}
}
Code:
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Oct 10, 2007 8:55 am     Reply with quote
The sleep() function doesn't mean 'pause' or 'wait' in CCS.
It puts the PIC into power-down mode. From the manual:
Quote:

Syntax: sleep(mode)
Parameters: None
Returns: Undefined
Function: Issues a SLEEP instruction. Details are device
dependent. However, in general the part will enter low power
mode and halt program execution until woken by specific external
events. Depending on the cause of the wake up execution may
continue after the sleep instruction. The compiler inserts a sleep()
after the last statement in main().
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