LPTMR clocked by MCGIRCLK

[vinkar]

Hello,

I am using the kl05-FRDM board. I am toggling a pin (LED) pin with the LPTMR0. This timer is clocked by the internal 32KH oscillator.

With a prescaler of 2 (divided by 2). It shld give me at least a period of (1/16000 = 62uSecs). This I did by putting '1' in the LPTMR0_CMR register.

Whenever there is a timeout it toggles a pin. But, always its in mscs and not uSecs.

Is there some error in this. I am posting my code below. Kindly help me

#include "derivative.h" /* include peripheral declarations */

int main(void)

{

        int count;

        uint16_t countTemp = 0;

          SIM_SOPT1 = 0x00040000;

          SIM_SCGC5 |= (SIM_SCGC5_LPTMR_MASK | SIM_SCGC5_PORTB_MASK);

          PORTB_PCR8 |= 0x00000100;    // alternative pin mux selection //

          GPIOB_PDDR |= 0x00000100;    // pin direction //

          SIM_SCGC5|=SIM_SCGC5_LPTMR_MASK;

          /* Reset LPTMR settings */

          SIM_SOPT1 = 0;

          SIM_SCGC5 |= (SIM_SCGC5_LPTMR_MASK | SIM_SCGC5_PORTB_MASK);

          LPTMR0_CSR=0;

          /* Set the compare value to the number of ms to delay */

          //LPTMR0_PSR = LPTMR_PSR_PCS(1)|LPTMR_PSR_PBYP_MASK;

          LPTMR0_PSR |=LPTMR_PSR_PBYP_MASK;

          //LPTMR0_PSR |=

          LPTMR0_CMR = 1;

          /* Start the timer */

          LPTMR0_CSR |= LPTMR_CSR_TEN_MASK;

          /* Wait for counter to reach compare value */

          while(1){

                  while (!(LPTMR0_CSR & LPTMR_CSR_TCF_MASK));

                  /* Disable counter and Clear Timer Compare Flag */

                  LPTMR0_CSR &= ~LPTMR_CSR_TEN_MASK;

                  LPTMR0_CSR |= LPTMR_CSR_TCF_MASK;

                  GPIOB_PTOR |= (1<<8);

                  LPTMR0_CSR |= LPTMR_CSR_TEN_MASK;

          }

}

[zhaohuiliu]

Hi,

For Freescale MCUs' clock configuration, it is better to review following chapters of RM once you have any issues:

1. chapter 3 for the IP's clock sources

2. chapter 5 for the MCU clock distribution

3. MCG/OSC chapter for the clock source availability

4. chapter SIM, for the clock switch details mentioned in chapter 3

Thanks,

Sandy

[zhaohuiliu · Accepted solution]

Hi,

Are you enable internal IRC for LPTimer? You should have the code to enable IRCLK before you enable LPTimer to run. Add following code to have a try?

MCG_C1 |= MCG_C1_IRCLKEN_MASK;

Sandy

[vinkar]

Thank u.

It works :smileyhappy: