Some simple questions about LPTMR

[m_mishrikey]

On S32K148 I was trying to use an LPTMR as a one-shot timer using different combinations of PEX calls.

I tried Init()/Deinit() and also StartCounter()/StopCounter(), but it seems to continue counting despite attempts to stop the timer.  

I did see some info about how you can't modify the timer registers once running, but I assume these calls would stop the running.

if(condition1){ 
   if(timer_flag){
     lockout = true;
     timer_flag = false;  // clear the ISR flag
        //LPTMR_DRV_StopCounter(INST_LPTMR1);
        //LPTMR_DRV_Deinit(INST_LPTMR1);
    }
   else if(!(LPTMR_DRV_IsRunning(INST_LPTMR1))){
     timer_flag = false;
     LPTMR_DRV_Init(INST_LPTMR1, &lpTmr1_config0, true);
   }
}
void LPTMR_ISR(void){
  LPTMR_DRV_Deinit(INST_LPTMR1);        
  timer_flag = true;
    /* Clear compare flag */
  LPTMR_DRV_ClearCompareFlag(INST_LPTMR1);
}

[m_mishrikey]

With your insight I was able to determine where I had a logic error.  The timer was getting restarted when it was not desired to restart.

In my ISR now I do:

1) set a flag for program code

2) LPTMR_DRV_StopCounter()

3) LPTMRM_DRV_ClearCompareFlag()

then in the program code when I want to start the counter all I need to do is call LPTRM_DRV_Init(inst, config, TRUE).

This works swimmingly as a one-shot.   Documenting here because the only examples I found were for periodic timing.

Thanks Robin!

[Robin_Shen · Accepted solution]

Sorry I may not understand your question, please correct me if I understand it wrong.

void LPTMR_ISR(void){
  timer_flag = true;
/* Clear compare flag */
  LPTMR_DRV_ClearCompareFlag(INST_LPTMR1);
}

Since you configured CSR[TFC]=0, CNR is reset whenever TCF is set.
I think after entering LPTMR_ISR, the CNR has actually been reset and will no longer increase.

LPTMR_DRV_GetCounterValueByCount can be used to check whether the CNR is still increasing.

Best Regards,
Robin
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