;******************************************************************************* ; 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 that must be added to P2.3 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 very infrequently to save power ; ACLK = n/a, MCLK = SMCLK = default DCO ; ; 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 ; ; MSP430G2x11 ; ; /|\ | XIN|; | | | ; -|RST XOUT|; | | ; + -|P1.1 P1.0| >LED ; | | | ; ===.1uf| | ; | | | ; + -|VSS ; ; D Dang ; Texas Instruments Inc ; October 2010 ; Built with Code Composer Essentials Version: 4.2.0 ;******************************************************************************* cdecls C,LIST, "msp430g2211.h" ; -.text ; Program Start ; -RESET mov.w #0280h,SP ; Initialize stackpointer mov.w #WDTPW+WDTHOLD,&WDTCTL ; Stop WDT bis.b #001h,&P1DIR ; P1.0 output mov.b #P2CA4,&CACTL2 ; P1.1 = CA1 ; Mainloop call #Batt_Check ; jmp Mainloop ; ; ; Batt_Check ; mov.b #CAREF0+CAON,&CACTL1 ; 0.25*Vcc on P2.3, Comp on Wait clr.w R15 ; Delay to R15 L1 dec.w R15 ; jnz L1 ; Delay over? mov.b #CARSEL+CAREF1+CAREF0+CAON,&CACTL1 ; 0.55V on -, Comp on bit.b #CAOUT,&CACTL2 ; clr.b &CACTL1 ; Disable Comp_A, save power jnc Batt_Low ; xor.b #001h,&P1OUT ; P1.0 toggle ret ; Batt_Low bis.b #001h,&P1OUT ; P1.0 set ret ; ; Interrupt Vectors ; -.sect ".reset" ; MSP430 RESET Vector short RESET ; end