example of LPC1837 capture timer?

[lpcware]

Content originally posted in LPCWare by smalouin on Mon Oct 27 06:37:05 MST 2014
Hello all,

I am trying to use the LPC1837 capture timer on port 5.0 (timer1 capture 0)... not having much luck (ie, I never get the IRQhandler for timer 1 called.

Anybody has an example that works?

Here is what I have, but it's all from scratch, I'm pretty sure an example would set me on the right track.

void rc5InterruptInit(void){
  /* Enable timer 1 clock and reset it */
   #define IR_TIMER              LPC_TIMER1
   #define IR_TIMER_IRQHANDLER   TIMER1_IRQHandler
   #define IR_TIMER_IRQn         TIMER1_IRQn

Chip_TIMER_Init(IR_TIMER);
Chip_RGU_TriggerReset(RGU_TIMER1_RST);
while (Chip_RGU_InReset(RGU_TIMER1_RST)) {}

/* Get timer 1 peripheral clock rate */
gRc5.timerFreq = Chip_Clock_GetRate(CLK_MX_TIMER1);

      
      /* Timer setup for match and interrupt at TICKRATE_HZ */
      Chip_TIMER_Reset(IR_TIMER);

      //Chip_SCU_PinMuxSet(5, 0, (SCU_MODE_INBUFF_EN | SCU_MODE_FUNC5));/* P5.0 pin as T1_CAP0 */
      Chip_SCU_PinMuxSet(5, 0, (SCU_MODE_FUNC5));/* P5.0 pin as T1_CAP0 */
      LPC_GIMA->CAP0_IN[1][0]=00000021;
      Chip_TIMER_TIMER_SetCountClockSrc(IR_TIMER,TIMER_CAPSRC_RISING_PCLK ,0);
      Chip_TIMER_ClearCapture(IR_TIMER,0);
      //Chip_TIMER_PrescaleSet(IR_TIMER,(gRc5.timerFreq /(RC5_FREQ)));
      Chip_TIMER_PrescaleSet(IR_TIMER,0);
      Chip_TIMER_CaptureEnableInt(IR_TIMER,0);/* start the capture timer */
      Chip_TIMER_CaptureFallingEdgeEnable(IR_TIMER,0);
      Chip_TIMER_CaptureRisingEdgeEnable(IR_TIMER,0);


Chip_TIMER_Enable(IR_TIMER);
      
/* Enable timer interrupt */
NVIC_EnableIRQ(IR_TIMER_IRQn);
NVIC_ClearPendingIRQ(IR_TIMER_IRQn);
}

void TIMER1_IRQHandler (void){
   
   /* using the capture compare */
   if (Chip_TIMER_CapturePending(IR_TIMER, 0)){
      rc5TimerCaptureIrq();
   }
}

[olivierswinkels]

I got exactly the same issue.

Did you eventually get it to work?

[isaacavila]

Hello All,

This is an example on LPCXpresso 4337 that uses P1_13 as the capture input for timer 0, you can use it as reference!

#include "board.h"
#include <stdio.h>
/*****************************************************************************
 * Private types/enumerations/variables
 ****************************************************************************/
#define TIMER_NUMBER        0
#define CAP_NUMB            0
#define LPC_TIMER            LPC_TIMER0
#define RGU_TIMER_RST        RGU_TIMER0_RST
#define LPC_TIMER_IRQ        TIMER0_IRQn
#define LPC_TIMER_IRQH        TIMER0_IRQHandler
/*****************************************************************************
 * Public types/enumerations/variables
 ****************************************************************************/
/*****************************************************************************
 * Private functions
 ****************************************************************************/
/*****************************************************************************
 * Public functions
 ****************************************************************************/
/**
 * @brief    Handle interrupt from 32-bit timer
 * @return    Nothing
 */
void LPC_TIMER_IRQH (void)
{
    static uint32_t times = 0;
    volatile static uint32_t captureValue = 0;
    /* Count how many times the interrupt has being trigger */
    times++;
    /* Get capture value on CAP0 */
    captureValue = Chip_TIMER_ReadCapture(LPC_TIMER, CAP_NUMB);
    DEBUGOUT(" %d\r\n", captureValue);
}
/**
 * @brief    main routine for blinky example
 * @return    Function should not exit.
 */
int main(void)
{
    SystemCoreClockUpdate();
    Board_Init();
    /* P1_13 as T0_CAP0, disable internal filter and enable input buffer */
    Chip_SCU_PinMuxSet(1, 13, (SCU_MODE_INBUFF_EN | SCU_MODE_ZIF_DIS | SCU_MODE_FUNC4));
    /* Timer 0 CAP0 EDGE enabled and SELECT as 0x2 */
    LPC_GIMA->CAP0_IN[TIMER_NUMBER][CAP_NUMB] = (2 << 4) | (1 << 1);
    /* Timer0 init */
    Chip_TIMER_Init(LPC_TIMER);
    /* Reset timer0 */
    Chip_RGU_TriggerReset(RGU_TIMER_RST);
    while (Chip_RGU_InReset(RGU_TIMER_RST));
    Chip_TIMER_Reset(LPC_TIMER);
    /* Select PCLK as timer source */
    Chip_TIMER_TIMER_SetCountClockSrc(LPC_TIMER, TIMER_CAPSRC_RISING_PCLK, CAP_NUMB);
    /* Select prescaler value */
    Chip_TIMER_PrescaleSet(LPC_TIMER, 10);
    /* Clear capture value on T0.CAP0 */
    Chip_TIMER_ClearCapture(LPC_TIMER, CAP_NUMB);
    /* Enable rising trigger on T0.CAP0 */
    Chip_TIMER_CaptureRisingEdgeEnable(LPC_TIMER, CAP_NUMB);
    /* Enable interrupt */
    Chip_TIMER_CaptureEnableInt(LPC_TIMER, CAP_NUMB);
    /* Enable timer interrupt */
    NVIC_ClearPendingIRQ(LPC_TIMER_IRQ);
    NVIC_EnableIRQ(LPC_TIMER_IRQ);
    /* Enable timer */
    Chip_TIMER_Enable(LPC_TIMER);
    while (1) {
    }
    return 0;
}

Hope this helps!

Regards,

Isaac

[yuanbinzhou]

Hi Isaac,

I have used example above to test the capture timer on lpcxpresso 4337 board. I have changed line 69 from TIMER_CAPSRC_RISING_PCLK to TIMER_CAPSRC_RISING_CAPN. However the value of "captureValue" always equals to zero, while I printed the value of "times", it changed really fast which of course exceed the frequency of my input signal. So strange about that. Any ideas about that?