Help Needed :PWM programming

Hi

I am using LPC2388 as target device . I configured Port1.28 as PWM output . below is the sample code , i am not able to see any wave form on oscilloscope.Please guide how to do it.

#include <LPC23xx.H>

static void PWM()
{
PINSEL3 |= 0x20 ;// select the function pwm for P1.18 pin
PWM1TCR = 0x02; /* reset PWM counter */
PWM1MCR = 0x02 ;//reset on match with PWM1MR0
PWM1PCR = 0x200 ; //enable PWM1.1 output and select it's function "single edge"
PWM1MR0 = 100 ;//
PWM1MR1 = 50;
PWM1TCR = 0x09 ;//enable pwm mode and the counter
PWM1LER = 0x03 ;//make match registers values effectif

}

}

int main(){
PWM();
while(1);

}

Thanks in advance
victory

I hope you have idea how fast your PWM is gonna work.. try to increase these values a bit.. how much is your PWM clock?

Hi Ajay

Thanks for the reply , my code is working now (mistake is PWM1LER should be 0x02) .
I have one more doubt i am writing PWM1MR0 =100 , this means what like pulse width is 100usec or 100 pulses. please clarify this.

In my next experiment i my looping back the same signal and want t o measure the pulse width .But i am not able to read the values ,i shorted P1.28 and P3.24 , please guide how to do it.Below is the code

#include <LPC23xx.H>

volatile unsigned int cap_count;
//----------------------------------------------------------------------------------
/* generating PWM */
static void PWMInit(){
PINSEL3 |= 0x20 ;// select the function pwm for P1.18 pin
PWM1TCR = 0x02; /* reset PWM counter */
PWM1MCR = 0x02 ;//reset on match with pWM1MR0
PWM1PCR |= 0x200 ; //enable PWM1.1 output and select it's function "single edge"
PWM1MR0 = 100 ;// pulse width
PWM1MR1 = 50; //duty cycle : 50%
PWM1TCR = 0x09 ;//enable pwm mode and the counter
PWM1LER = 0x02 ;//make match registers values effect
}

//-----------------------------------------------------------------------------------
/* Measuring the Pulse width*/
/* shorting p1.28 and p3.24*/
void Timer1_cap_init(void) {
PINSEL7=0x00020000; /*Capture input on port p3.24 */
T0PR=0x00000018; /* input clock for timer1 :120kHz */
T0TCR=0x02; /* reset the counter*/
T0CCR=0x05; /* count on every rising edge */
T0TCR = 0x01; /*Enable the counter */
}

//------------------------------------------------------------------------------------
int main(){
PWMInit();
Timer1_cap_init();
//cap_count = T0CR0;
while(1){
cap_count = T0CR0; //reading the pulse width.

}

}

//-------------------------------------------------------------------------------------

100 means till your TC counts 100. which will be equal to 100 * 1/Tclock in time.

Your pulse is way too small. I am not looking deeply into your code just make sure you start and stop capture triggered by external event.