LPTMR clocked by MCGIRCLK

vinkar — Tue, 18 Mar 2014 19:10:52 GMT

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;

}

Re: LPTMR clocked by MCGIRCLK

zhaohuiliu — Wed, 19 Mar 2014 06:26:49 GMT

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

Re: LPTMR clocked by MCGIRCLK

vinkar — Wed, 19 Mar 2014 09:51:54 GMT

Thank u.

It works :smileyhappy:

Re: LPTMR clocked by MCGIRCLK

zhaohuiliu — Thu, 20 Mar 2014 05:40:08 GMT

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

topic Re: LPTMR clocked by MCGIRCLK in Kinetis Microcontrollers

LPTMR clocked by MCGIRCLK

Re: LPTMR clocked by MCGIRCLK

Re: LPTMR clocked by MCGIRCLK

Re: LPTMR clocked by MCGIRCLK