//****************************************************************************** // MSP430G2x11 Demo - Comp_A, 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 between P2.3 and Vss is first charged // to 0.25*Vcc and then compared to ~0.55V If 0.25*Vcc, // is above ~0.55V, P1.0 is toggled, else set Batt_Check is called // constantly in an endless loop - in an actual application, Batt_Check // should be called infrequently to save power // ACLK = n/a, MCLK = SMCLK = default DCO // // There is a tolerance 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 // // MSP430G2x11 // // /|\ | XIN|// | | | // -|RST XOUT|// | | // + -|P1.1/CA1 P1.0| >LED // | | | // ===.1uf| | // | | | // + -|Vss // void Batt_Check(void); unsigned int i; // // D Dang // Texas Instruments Inc // October 2010 // Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10 //****************************************************************************** #include void main (void) { WDTCTL = WDTPW + WDTHOLD; P1DIR |= 0x01; CACTL2 = P2CA4; while (1) { Batt_Check(); } } // // // // Stop WDT P1.0 output P1.1 = CA1 Mainloop void Batt_Check(void) { CACTL1 = CAREF_1 + CAON; // 0.25*Vcc on P1.1, Comp on i = 16384; // delay while(i>0) { i ; } CACTL1 = CARSEL + CAREF_2 + CAREF_1 + CAON; // 0.55V on -, Comp on if (CACTL2 & CAOUT) P1OUT ^= 0x01; // P1.0 toggle else P1OUT |= 0x01; // P1.0 set CACTL1 = 0x00; // Disable Comp_A, save power }