amal sebastian

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12 years, 4 months ago.

problem on pwm interrupt

I am using LPC 1768 board....I wrote a program for creating interrupt when counter matches with match 0 register.....but its not entering into interrupt program....led3 is not toggling...please help...attached c prog /media/uploads/amalsebastian1992/prog3.txt

Erik, do you have an example on how to do this with the LPC11U24?

posted by Very Compact 16 Feb 2015

2 Answers

Erik -
12 years, 4 months ago.

(You can still put it between <<code>> and <</code>> here, thats easier for everyone).

Anyway, looked at it, and three things:

First of all, I assume the wait(0.2) in your IRQ handler is just for debugging purposes, otherwise it is really bad ;).

Next, one of those small irritating errors (I actually copied your code to blink a led in the main loop, and it didn't do anything even after I deleted everything else in the program, only then I realised it):

chB != chB; //This only checks if chB is unequal to chB, which is false, and then it doesn't do anything else.

chB = !chB; //This one makes chB the inverse of its current value, and is the one you want

Finally the main problem, I expected since you used 'PWM1_IRQHandler', that that is the default PWM1_IRQHandler location, apparently it isn't. The default way I use the hardware IRQs fixes it though, before you enable the IRQ, add the following line:

NVIC_SetVector(PWM1_IRQn, (uint32_t)&PWM1_IRQHandler);

With that you can redirect the IRQ vector to any function you want.

Then the code works for me, just to be sure, here it is:

#include "mbed.h"
 
void PWMInit();
 
 PwmOut chA(p23);
 DigitalOut chB(LED3);
 
int main (void)
{
    PWMInit();
 
    while(1) {
 
 
  LPC_PWM1->MR3 = 6000;
        LPC_PWM1->MR4 = 15000;
        LPC_PWM1->LER |=  (1<<3) | (1<<4) ;
        
 
    
 
    }
 
}
 
 
 void PWM1_IRQHandler (void) 
{
    if((LPC_PWM1->IR & 0x01) == 0x01) // Check whether it is an interrupt from match  0
    {
   
        chB = !chB;
        wait(.2);
        
        LPC_PWM1->IR |= 1<<0; // Clear the interrupt flag
        }
        
        
    
    return;
}
 
void PWMInit()
{
    LPC_SC->PCONP |= 1 << 6; // enable power for PWM1
    LPC_SC->PCLKSEL0 |= 1 << 12; // PCLK_PWM1 = CCLK
 
    LPC_PWM1->MR0 = 16000; // PWM freq = CCLK/16000
    
    LPC_PWM1->MCR |= 1 << 0; // interrupt on Match0
 
    LPC_PINCON->PINSEL3 |= (2 << 14 ); // P2.4 works as PWM1 output
    LPC_PINCON->PINMODE3 |= 2 << 14; // enable neither pull up nor pull down
 
 
    LPC_PWM1->PCR |= 1 << 4; // Configure channel 4 as double edge controlled PWM
    LPC_PWM1->PCR |= 1 << 12; // Enable PWM channel 4 output
 
    LPC_PWM1->MR0 = 16000; // PWM freq = CCLK/16000
 
    LPC_PWM1->TCR = (1 << 0) | (1 << 3); // enable timer counter and PWM
    
     
    NVIC_SetVector(PWM1_IRQn, (uint32_t)&PWM1_IRQHandler);
    NVIC_EnableIRQ(PWM1_IRQn);
    return;
      }

Accepted Answer

same code i am using .but when i add NVIC_SetVector(PWM1_IRQn, (uint32_t)&PWM1_IRQHandler); in my code for LPC1768.it showing undefined function.its not defined in core_cm3.c file.

please give any suggestion for my error.thanks in advance

posted by trupti bhakare 07 Jun 2016
amal sebastian
poster
12 years, 4 months ago.

thank you erik...:)...its working perfectly