fet140_ta_capture.c

msp430f14x 系列片内外设的实例代码

//***********************************************************************
//  MSP-FET430P140 Demo - Timer_A0 capture of ACLK/8 using SMCLK
//
//  Description;  Input Capture of ACLK/8 on P1.1(TA0)
//  Place breakpoint at the mentioned instruction to see 16 capture
//  values and the differences
//
//  ACLK = 32768 Hz, MCLK = SMCLK = Default ~800 Khz
//
//
//                MSP430F149
//             -----------------
//         /|\|              XIN|-  
//          | |                 |32768 Hz
//          --|RST          XOUT|-     |
//            |             P1.1|<-----|
//            |             P1.0|--->LED
//
//  Harman Grewal
//  Texas Instruments Inc
//  July 2004
//  Updated for IAR Embedded Workbench Version: 2.21B
//********************************************************************

#include  <msp430x14x.h>

unsigned int new_cap=0;
unsigned int old_cap=0;
unsigned int cap_diff=0;

unsigned int diff_array[16];            // RAM array for difference in captures
unsigned int capture_array[16];         // RAM array for captures
unsigned char index=0;
unsigned char count = 0;

void main(void)
{ 
  volatile unsigned int i;
  WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer
  for (i=0; i<20000; i++)               // Delay for crystal stabilization
  {
  }  
  P1DIR = 0x01;                         // Set P1.0 out,1.1 input direction
  P1OUT &= ~0x01;                       // LED off
  P1SEL = 0x02;                         // Set P1.1 to TA0
  P2DIR = 0x01;                         // P2.0-ACLK
  P2SEL |= 0x01;
  BCSCTL1 |= DIVA_3;                    // ACLK/8
  
  CCTL0 = CM_1 + SCS + CCIS_0 + CAP + CCIE;// Rising edge + CCI0A (P1.1) + Capture Mode + Interrupt
 
  TACTL = TASSEL_2 + MC_2;              // SMCLK + Continuous Mode
                                        
  _BIS_SR(LPM0_bits + GIE);             // LPM0 + Enable global ints  
    
}

#pragma vector=TIMERA0_VECTOR
__interrupt void TimerA0(void)
{
   new_cap = TACCR0;
   cap_diff = new_cap - old_cap;              

   diff_array[index] = cap_diff;        // record difference to RAM array
   capture_array[index++] = new_cap;
   if (index == 16)
   {
    index = 0;
    P1OUT ^= 0x01;                       // Toggle P1.0 using exclusive-OR
   }                         
   old_cap = new_cap;                   // store this capture value
   count ++;
   if (count == 32)
   {
    count = 0;
    _NOP();
   }
   
}