波占空比，通过滤波，输出直流模拟量。

//

CMOD=0x02;//Setup PCA timer

CL=0x00;

CH=0x00;

CCAP0L=p_on;//Set the initial value same as CCAP0H

CCAPM0=0x42;//0100,0010 Setup PCA module 0 in PWM mode

CCAP1L=p_on;//Set the initial value same as CCAP0H

CCAP1H=p_on;//25% Duty Cycle

//CCAPMn.1

CCAPM1=0x42;//0100,0010 Setup PCA module 0 in PWM mode

CCAP2L=p_on;//Set the initial value same as CCAP0H

CCAP2H=p_on;//25% Duty Cycle

//CCAPMn.1

CCAPM2=0x42;//0100,0010 Setup PCA module 0 in PWM mode

CCAP3L=p_on;//Set the initial value same as CCAP0H

CCAP3H=p_on;//25% Duty Cycle

//CCAPMn.1

CCAPM3=0x42;//0100,0010 Setup PCA module 0 in PWM mode

int i;

for(i=0;i<a;i++);

unsigned char i=0;

init_pwm();

CR=1;//Start PCA Timer

while(1)

{

while(++i)

{

pulse_0(i+50);

pulse_1(i+100);

pulse_2(i+150);

pulse_3(i+200);

delay(1000);

}

while(--i)

{

pulse_0(i+50);

pulse_1(i+100);

pulse_2(i+150);

pulse_3(i+200);

delay(1000);

}

}