topic LPTMR KL05 in Kinetis Microcontrollers

LPTMR KL05

filipebranco — Tue, 18 Mar 2014 15:04:51 GMT

Hello,

I'm facing some problems using the KL05 FRDM board and i'm trying to toggle a pin using the LPTMR.
The LPTMR is clocked by the MCRIRCLK (32KHz) and i'm using a prescaler of 2 so the clock would be 16Khz. The result that i'm getting is 2msecs instead of 60uSecs.

Please find the code below:

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

int main(void)

{

SIM_SOPT1 |= (0<<18); //32K Oscillator clock

SIM_SOPT1 |= (0<<19);

SIM_SOPT1 = 0x00000000;

SIM_SCGC5 |= (SIM_SCGC5_LPTMR_MASK | SIM_SCGC5_PORTB_MASK);// LPTMR gated PORTB

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

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

asm(" CPSIE i");

NVIC_ICPR = 1 << (28);

NVIC_ISER = 1 << (28);

LPTMR0_CSR=0;

LPTMR0_CSR |= 0x00000040; // HEX timer interrupt Enable

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

LPTMR0_PSR = LPTMR_PSR_PCS(1)|LPTMR_PSR_PBYP_MASK;

LPTMR0_CMR = 10; //Check what is the lowest we can get ?

/* Start the timer */

LPTMR0_CSR |= LPTMR_CSR_TEN_MASK;

}

void LPTimer_IRQHandler(void){

LPTMR0_CSR &= ~LPTMR_CSR_TEN_MASK;

LPTMR0_CSR |= LPTMR_CSR_TCF_MASK;

GPIOB_PTOR |= (1<<8);

LPTMR0_CSR |= LPTMR_CSR_TEN_MASK;

}

If anyone knows why this is happening please let me know.

Many Thanks

Filipe Branco

Re: LPTMR KL05

perlam_i_au — Fri, 21 Mar 2014 21:45:13 GMT

I think you are setting by error the LPO 1kHz instead of the System oscillator, I suggest you to comment or delete the lines:

SIM_SOPT1 |= (0<<18); //32K Oscillator clock

SIM_SOPT1 |= (0<<19);

Here you are setting to use the LPO (OSC32KSEL= 11 = LPO 1kHz) this perfectly explain your 2msec period

Have a nice day :P,
Perla

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Re: LPTMR KL05

KL04_user — Thu, 19 Jun 2014 05:17:14 GMT

Hi,

isint he already clearing the settings set by

SIM_SOPT1 |= (0<<18);

SIM_SOPT1 |= (0<<19);

by the third line

SIM_SOPT1 = 0x00000000; and selecting System oscillator (OSC32KCLK)??

Also, these lines

SIM_SOPT1 |= (0<<18);

SIM_SOPT1 |= (0<<19);

have no effect as 0 is being shifted so many times!!!

Am also struck with a similar problem. Any suggestions would be helpful..

Thanks in advance

Re: LPTMR KL05

mjbcswitzerland — Thu, 19 Jun 2014 10:55:15 GMT

SIM_SOPT1 is relevant for the RTC and not the LPTMR.

The LPTMR clock source is defined in LPTMR0_PSR.

If using the external oscillator as clock input, the external oscillator input connection must also be enabled in OSC0_CR (irrespective of whether the oscillator is running or not).

Therefore:

	OSC0_CR \|= (OSC_CR_ERCLKEN \| OSC_CR_EREFSTEN);	// enable the external reference clock and keep it enabled in stop mode
	LPTMR0_PSR = (LPTMR_PSR_PCS_OSC0ERCLK \| LPTMR_PSR_PBYP);

This will clock the LPTRM from the oscillator input.

Regards

Mark

Re: LPTMR KL05

KL04_user — Thu, 19 Jun 2014 20:37:33 GMT

Thanks Mark.. That explains a lot.