CC2540 16 bit TIMER-PULSE/SPACE WIDTH MEASURE

Hi Daron,

If you use the </> button on the forum text editor you can paste the code in with formatting.

To your question - I don't know if I really understand what you are going to do. But it looks like you are not using the capture mode of the timer.

We don't have any published examples of this (I think) but below is a small function I made once that uses the T1 capture mode and DMA to store pulse lengths. DMA stores the T1 capture register 0x62A6 to &timercapture. You could change timerCapture to be an array. Also please note that the comments for the DMA initialization is wrong.

In the example it is used to calculate a frequency based on time difference after a number of pulses, but you could use the DMAIRQ to read out the latest values in an ISR if you want. That would be more robust than IO ISR and reading T1.

#include "freqCapture.h"
#include "hal_dma.h"


volatile uint16 timerCapture;
volatile double frequency = 0;
volatile double ticksAvg;
volatile double firstCap;
volatile double lastCap;


void timerCaptureArmDMA()
{
  halDMADesc_t *ch;

  ch = HAL_DMA_GET_DESC1234( T1CAP_DMA_CH );

  // Abort any pending DMA operations (in case of a soft reset).
  HAL_DMA_ABORT_CH( T1CAP_DMA_CH );

  // The start address of the destination.
  HAL_DMA_SET_DEST( ch, &timerCapture );

  // Using the length field to determine how many bytes to transfer.
  HAL_DMA_SET_VLEN( ch, HAL_DMA_VLEN_USE_LEN );

  // One byte is transferred each time.
  HAL_DMA_SET_WORD_SIZE( ch, HAL_DMA_WORDSIZE_WORD );

  // The bytes are transferred 1-by-1 on Tx Complete trigger.
  HAL_DMA_SET_TRIG_MODE( ch, HAL_DMA_TMODE_SINGLE );
  HAL_DMA_SET_TRIG_SRC( ch, HAL_DMA_TRIG_T1_CH0 );

  // The source address is incremented by 1 byte after each transfer.
  HAL_DMA_SET_SRC_INC( ch, HAL_DMA_SRCINC_0 );

  // The destination address is constant - the T1 Compare 1.
  HAL_DMA_SET_DST_INC( ch, HAL_DMA_DSTINC_0 ); //HAL_DMA_DSTINC_1

  // The DMA transfer done is serviced by ISR in order to maintain full thruput.
  HAL_DMA_SET_IRQ( ch, HAL_DMA_IRQMASK_DISABLE );

  // Xfer all 8 bits of a byte xfer.
  HAL_DMA_SET_M8( ch, HAL_DMA_M8_USE_8_BITS );

  // DMA has highest priority for memory access.
  HAL_DMA_SET_PRIORITY( ch, HAL_DMA_PRI_HIGH);
  
  HAL_DMA_SET_LEN( ch, NUM_CAPTURES);
  
  HAL_DMA_SET_SOURCE(ch, 0x62A6);
  
  HAL_DMA_ARM_CH( T1CAP_DMA_CH );
  
  HAL_DMA_CLEAR_IRQ( T1CAP_DMA_CH );
}




void initFreqCapture()
{
  P0DIR &= ~(1<<2);
  P0SEL |= (1<<2);
  P2DIR |= 0x2 << 6;
  uint8 cnt = 1;
}
  
 
double freqCapture()
{
    // Intialize timer
    T1CTL = 0;
    T1CNTL = 0;
    T1CCTL0 = 0; // Reset Ch0 mode so we don't get spurious '0' DMA-copies on next iteration.
    T1STAT = ~(1 << 0);

    // Set up DMA to copy from T1CC0 to someplace.
    timerCaptureArmDMA();
    DMAIRQ = ~(1<<2);
    // Set timer1 input capture
    T1CCTL0 = (0x01 << 0) | (1 << 6); // Capture type, IM=0
    T1CTL = 1;
    while( 0 == (T1STAT & 1) );
    firstCap = T1CC0L; // Get the first one directly.
    
    //Wait for X edges
    while( ( DMAIRQ & (1<<2) ) == 0);

    // Turn off timer
    T1CTL = 0;
    T1CNTL = 0;
    T1CCTL0 = 0; // Reset Ch0 mode so we don't get spurious '0' DMA-copies on next iteration.
    T1STAT = ~(1 << 0);
    
    // Calculate frequency
    lastCap = timerCapture;
    ticksAvg = (lastCap-firstCap)/NUM_CAPTURES;
    frequency = 32 / ticksAvg;
    
    asm("nop");
    return frequency;
}

I hope that helps. Unfortunately there are a few hard-coded values in there instead of defines, but you seem to have the hang of this.

Best regards,
Aslak

Thanks for your answer, Aslak. I m trying to design sensor part of full project...I solved my problem myself. Timer1 Init must be like this for my code;
T1CTL=0x00;
T1CNTL=0;
T1CTL = 0x01;
Actually, i focused on how can i read timer value without compare match(no compare match because it is incompatible with state machine structure in mycode). I thought, timer was truely running, but even uninitialized!!!! :D