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Timer interrupt for led blinking is not working.

Hi.. I am trying to blink an led using a timer interrupt. Connected the led to P0.0 and the code is as shown below. Is there any problem with the code??


#include<lpc21xx.h>

void __irq timer0(void);
void timersetup(void);

int main()
{
        PINSEL0 = 0x00000000;
        PINSEL1 = 0x00000000;
        IODIR0 = 0x01;
        IOSET0=0x01;
        timersetup();

        while(1);
}

void timersetup(void)
{
        VICIntSelect=0x0;
        VICVectCntl0=0x20|4;
        VICVectAddr0=(unsigned long)timer0;
        VICIntEnable=(1<<4);

        T0TCR = 0x02;  //Reset the timer0
        T0PR=0x00;     //Set prescaler to 0
        T0MR0=0x0FFF;  //Match register value
        T0IR=0x01;     //Clear match0 interrupt
        T0MCR= 0x03;   //Enable interrupt on MR0 and enable Reset on MR0
        T0TCR = 0x01;   //Start timer0
}

void __irq timer0(void)
{
        IOPIN0^=0x01;   //Toggle LED on p0.0
        VICVectAddr=0;
        T0IR=0x01;      //Reset match0 interrupt

}

Parents

0 Navinar Savad over 11 years ago in reply to John Linq

Sorry John. I forgot to mention that I got it working, but the problem was in how the delay was set up, and you are right of course. I loaded my code using ISP so Fosc was set to 10 to 25Mhz. I read up on PLL and configured the PLL for 12Mhz, and now the LED is blinking ok. I have not made any other major change to the code, and the below code works correctly. It provides 1 sec delay. Thanks everyone for your help and prompt reply. I really appreciate it!!

Details for the code are:
For PLL: M=1, P=8... Selected cclk=12Mhz and Fosc=12Mhz.. Refer to datasheet of lpc2129 for details on configuring PLL. Selection of Fosc is also given there.

As clock is 12Mhz, 1 tick=1/12MHz= 0.083 microseconds.
So for 1 ms, no.of ticks= 1ms/.083us=12048192 (dec) = 0xB7D740 (hex).. I hav given this value in T0MR0 for matching to the timer. Checked and confirmed that 1s delay occurs.

Thanks again... :-)


#include<lpc21xx.h>

void init_pll(void);        //initialise PLL
void __irq timer0(void);    //Interrupt routine for timer0
void timer_setup(void);     //Setup timer

int main()
{
        VPBDIV= 0x01;
        init_pll();
        timer_setup();
        PINSEL0 = 0x00000000;
        IODIR0 = 0x01;     //LED connected to P0.0

        while(1);
}

void init_pll(void)
{
        PLLCFG = 0x60;  //For 12Mhz operation: M=1,P=8
        PLLCON = 0x01;   //Enable PLL
        while(!(PLLSTAT & 0x00000400));   //Check for lock condition (bit 10)
        PLLCON = 0x03;   //Enable and connect PLL
        PLLFEED = 0x0AA; //Write to PLLFEED to activate PLL
        PLLFEED = 0x055; //Same as above.. Mandatory steps.
}

void timer_setup(void)
{
        T0PR    =       0x00;     //Prescaler to 0. Timer same as cclk
        T0MR0   =       0xB7D740; //For 12 Mhz operation
        T0MCR   = 0x03;            //Select interrupt and reset bits in register
        T0TCR = 0x01;             //Enable the timer

        VICIntSelect = 0x00000000;  //All IRQ
        VICVectCntl0 = 0x20|4;      //Select timer0 interrupt with highest priority
        VICVectAddr0 = (unsigned long)timer0; //Assign address for timer0
        VICIntEnable = (1<<4);      //Enable timer0 interrupt
}

void __irq timer0(void)
{
        T0IR    = 0x01;     //Clear Timer interrupt
        IOPIN0 ^= 0x01;   //Toggle LED
        VICVectAddr=0x0;   //Reset interrupt
}

Hopes this helps others.. Will come soon with some other doubt!! ;-)

Reply

0 Navinar Savad over 11 years ago in reply to John Linq

Details for the code are:
For PLL: M=1, P=8... Selected cclk=12Mhz and Fosc=12Mhz.. Refer to datasheet of lpc2129 for details on configuring PLL. Selection of Fosc is also given there.

Thanks again... :-)


#include<lpc21xx.h>

void init_pll(void);        //initialise PLL
void __irq timer0(void);    //Interrupt routine for timer0
void timer_setup(void);     //Setup timer

int main()
{
        VPBDIV= 0x01;
        init_pll();
        timer_setup();
        PINSEL0 = 0x00000000;
        IODIR0 = 0x01;     //LED connected to P0.0

        while(1);
}

void init_pll(void)
{
        PLLCFG = 0x60;  //For 12Mhz operation: M=1,P=8
        PLLCON = 0x01;   //Enable PLL
        while(!(PLLSTAT & 0x00000400));   //Check for lock condition (bit 10)
        PLLCON = 0x03;   //Enable and connect PLL
        PLLFEED = 0x0AA; //Write to PLLFEED to activate PLL
        PLLFEED = 0x055; //Same as above.. Mandatory steps.
}

void timer_setup(void)
{
        T0PR    =       0x00;     //Prescaler to 0. Timer same as cclk
        T0MR0   =       0xB7D740; //For 12 Mhz operation
        T0MCR   = 0x03;            //Select interrupt and reset bits in register
        T0TCR = 0x01;             //Enable the timer

        VICIntSelect = 0x00000000;  //All IRQ
        VICVectCntl0 = 0x20|4;      //Select timer0 interrupt with highest priority
        VICVectAddr0 = (unsigned long)timer0; //Assign address for timer0
        VICIntEnable = (1<<4);      //Enable timer0 interrupt
}

void __irq timer0(void)
{
        T0IR    = 0x01;     //Clear Timer interrupt
        IOPIN0 ^= 0x01;   //Toggle LED
        VICVectAddr=0x0;   //Reset interrupt
}

Hopes this helps others.. Will come soon with some other doubt!! ;-)

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