test44x_ca03.c

WDT

//******************************************************************************
//  MSP430-tesr44x Demo - Comp_A Used For Simple 2.2V Low Battery Detect  
//
//  Description; Two comparator_A reference generators 0.25*Vcc and ~ 0.55V 
//  are compared for a simple battery check of 2.2V. In the subroutine 
//  Batt_Check a small capacitor that must be added to P1.6 is first charged
//  to 0.25*Vcc and then compared to ~ 0.55V. If Vcc, assumed to be the battery
//  level is above ~0.55V, P5.1 is toggled, else set. Batt_Check is called
//  constantly in an endless loop - in an actual application, Batt_Check
//  should be called very infrequent to save power. 
//  ACLK = n/a, MCLK = SMCLK = default DCO ~ 800k 
//
//  There is a tolerence of the Comp_A reference generator and in the 
//  device specific datasheet. In most applications, the tolerence of the
//  reference generator is more than adequate to detect Low Battery.  
//
//		 MSP430F449
//            -----------------
//       /|\ |              XIN|-  
//        |  |                 |
//        ---|RST          XOUT|-
//           |                 | 
//     +-----|P1.6         P5.1|-->LED   
//     |     |                 |
//    ===.1uf|                 |
//     |     |                 |			
//     +-----|VSS
//
void Batt_Check(void);
unsigned int i;  
//
//  Yang Rui
//  Lierda, Inc
//  MAY  2004
//  Built with IAR Embedded Workbench Version: 1.26B
//******************************************************************************
#include  "msp430x44x.h"

void main (void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P5DIR |= 0x02;                            // P5.1 output
  CACTL2 = P2CA0;                           // P1.6 = CA0
  while (1)                                 // Mainloop
  {
    Batt_Check();
  }
}

void Batt_Check(void) {
  CACTL1 = CAREF_1 + CAON;                  // 0.25*Vcc on P2.3, Comp. on
  i = 16384;                                // delay
  while(i>0) {
    i--;
  }
  CACTL1 = CARSEL + CAREF_2 + CAREF_1 + CAON; // 0.55V on -, Comp. on
  if ((CACTL2 & CAOUT) > 0)                 
    P5OUT ^= 0x02;                          // P1.0 toggle
  else P5OUT |= 0x02;                       // P1.0 set
  CACTL1 = 0x00;                            // Disable Comp_A, save power
}