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is these same?

 
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luckyluke



Joined: 18 Apr 2006
Posts: 45

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is these same?
PostPosted: Sun Feb 17, 2019 4:34 am     Reply with quote
hello
i am controlling two motors with h-bridge controller.
i want to ask a question about frequent update of pwm duty.
Code:

#include <18f2520.H>
#fuses XT, NOWDT,NOBROWNOUT,PUT,NOLVP,NOMCLR
#use delay(clock=4000000)

void main(){
setup_timer_2(T2_DIV_BY_4,200,6);
setup_timer_1 ( T1_INTERNAL | T1_DIV_BY_1 );
setup_ccp1(CCP_PWM);
setup_ccp2(CCP_PWM);

while(1){
   while (!interrupt_active(INT_TIMER1));
     clear_interrupt(INT_TIMER1);
     set_timer1(64536);
     set_pwm1_duty(200);
     set_pwm2_duty(200);
}


Code:

#include <18f2520.H>
#fuses XT, NOWDT,NOBROWNOUT,PUT,NOLVP,NOMCLR
#use delay(clock=4000000)

void main(){
 setup_timer_2(T2_DIV_BY_4,200,6);
 setup_timer_1 ( T1_INTERNAL | T1_DIV_BY_1 );
 setup_ccp1(CCP_PWM);
 setup_ccp2(CCP_PWM);

 set_pwm1_duty(200);
 set_pwm2_duty(200);

while(1){
   while (!interrupt_active(INT_TIMER1));
     clear_interrupt(INT_TIMER1);
     set_timer1(64536);
}


so is these code same for motor?
Ttelmah



Joined: 11 Mar 2010
Posts: 19238

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PostPosted: Sun Feb 17, 2019 5:35 am     Reply with quote
The PWM gets updated on the next cycle, and since the update is to the same number it'll remain unchanged.

Honestly 'better' to make your indentation reflect actual operations:

Code:

while(1)
{
    while (!interrupt_active(INT_TIMER1))
        ; //This is the operation being handled by the 'while'
    clear_interrupt(INT_TIMER1); //these lines are not
    set_timer1(64536);
    set_pwm1_duty(200);
    set_pwm2_duty(200);
}


Otherwise it is terribly easy to forget which operations are in which loop
luckyluke



Joined: 18 Apr 2006
Posts: 45

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PostPosted: Sun Feb 17, 2019 6:15 am     Reply with quote
It was for fixed 1 ms interval.
I intended to fill 1ms with\
Code:
 while (!interrupt_active(INT_TIMER1)) ;

Actual program is like:
Code:

while(1)
{
    while (!interrupt_active(INT_TIMER1))
       ;
    clear_interrupt(INT_TIMER1);
    set_timer1(64536);
    sensor_read();
    decision();
    motor();
}

Is this wrong logic or bad for readability?
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