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Problem with the production of pwm wave

 
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qwwe



Joined: 17 Sep 2017
Posts: 59

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Problem with the production of pwm wave
PostPosted: Thu Nov 23, 2017 3:18 am     Reply with quote

Hi, I wrote the following program to generate a pwm wave
Code:

#include <16f1823.h>
#device *=16
#fuses NOWDT            //NO Watch Dog Timer
#fuses PUT            //Power Up Timer
#fuses NOLVP          //No low voltage programing
#fuses NOCPD          //No EE protection
#fuses NOPROTECT      //Code not protected from reading
#fuses NOWRT          //Program memory not write protected
#fuses NODEBUG        //No Debug mode for ICD
#fuses NOBROWNOUT     //No brownout reset
#USE DELAY (clock=1000000,int)
#include <stdio.h>
#include <string.h>

void main()
{
set_tris_c(0b11101111);
output_low(PIN_C5);
setup_timer_2(T2_DIV_BY_1,20,1);

setup_ccp1(ccp_pwm);
set_pwm1_duty(512);

while(TRUE)
{
}
}

According to the above, the program now needs to generate a wave at 12 khz frequencies،But does not produce.
Of course, the low frequencies are up to 1khz by changing the settings, but no more.
Meanwhile, I want to use the micro-clock internal, whether the setting is correct.
Thank you for saying what the problem is
qwwe



Joined: 17 Sep 2017
Posts: 59

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PostPosted: Thu Nov 23, 2017 3:49 am     Reply with quote

Is this microcontroller digital converter analog
If it has ccs commands to use it
Ttelmah



Joined: 11 Mar 2010
Posts: 12824

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PostPosted: Thu Nov 23, 2017 4:43 am     Reply with quote

The problem is your duty cycle.

You have a PR2 value of 20.
Duty max (for full on) = (PR2+1)*4 = 84

You are loading 512 for the duty, so the output will be permanently high.

Look at the examples in the data sheet (table 24-5, 6 & 7. Note how the maximum resolution shoots down as the PR2 value goes down.

set_pwm1_duty(42L);

Would be a starting value.
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