High Frequency Digital Input Sampling with CC2540

/*
 *  Filename:       freqCapture.c
 *  Revised:        15.12.2015
 *  Revision:       1.0
 *
 *  Description:    Frequency capture sample code
 *
 *
 *  Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/ 
 * 
 * 
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 *  modification, are permitted provided that the following conditions 
 *  are met:
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 *    notice, this list of conditions and the following disclaimer.
 *
 *    Redistributions in binary form must reproduce the above copyright 	
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the   
 *    distribution.
 *
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 *    its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
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*/


#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;
}