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PWM half Bridge Problem

 
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azykazy



Joined: 05 Oct 2011
Posts: 11
Location: South Africa

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PWM half Bridge Problem
PostPosted: Wed Oct 05, 2011 3:43 am     Reply with quote

Hi All,

I have a problem making the half bridge PWM work on 18F4550.

Code:

#include<18f4550.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)

void main()
{
unsigned int pwm1;

pwm1=0;
setup_ccp1(CCP_PWM_HALF_BRIDGE | CCP_PWM_H_H);
setup_timer_2(T2_DIV_BY_16, 249, 1);
pwm1=120; //duty cycle
set_pwm1_duty(pwm1);
while(TRUE)
{
}   
}

When i simulate on Proteus, P1A has an output and P1B is 0.

Any ideas?

Compiler Version is 4.093
Ttelmah



Joined: 11 Mar 2010
Posts: 13654

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PostPosted: Wed Oct 05, 2011 7:34 am     Reply with quote

You need to set the TRIS.
The compiler unfortunately gets confused by using the standard PWM commands, and doesn't realise that TRIS D5, needs to be set to zero for P1B to output.
Code:

#include<18f4550.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
 
void main(void) {
   unsigned int pwm1;
   pwm1=0;
   setup_ccp1(CCP_PWM_HALF_BRIDGE | CCP_PWM_H_H);
   setup_timer_2(T2_DIV_BY_16, 249, 1);
   pwm1=120; //duty cycle
   output_drive(PIN_D5);
   set_pwm1_duty(pwm1);
   do {
   } while(TRUE); //This avoids the compiler error message 
}


Best Wiishes
azykazy



Joined: 05 Oct 2011
Posts: 11
Location: South Africa

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PostPosted: Wed Oct 05, 2011 7:41 am     Reply with quote

Thanks Very Happy

I have tried it and it works!

Much appreciated!
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