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初学430,下面CCS里自带的MSP430G2553的例程,不太明白它的意思,给的图解也不明白,是怎么跟2.2V搞上关系的?另外运行例程2,0.55V的管脚输出有1V多,0.5*Vcc和0.25*Vcc的都与理论值相差很大,求解答。
// 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.
//
// MSP430G2x13/G2x53
// -----------------
// /|\ | XIN|-
// | | |
// ---|RST XOUT|-
// | |
// +-----|P1.1/CA1 P1.0|-->LED
// | | |
// ===.1uf| |
// | | |
// +-----|Vss
//
void Batt_Check(void);
unsigned int i;
//
// D. Dang
// Texas Instruments Inc.
// December 2010
// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10
//******************************************************************************
#include <msp430.h>
int main (void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P1DIR |= 0x01; // P1.0 output
CACTL2 = P2CA4; // P1.1 = CA1
while (1) // Mainloop
{
Batt_Check();
}
}
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
}
例程2:
// MSP430G2x13/G2x53 Demo - Comp_A, Output Reference Voltages on P1.1
//
// Description: Output Comparator_A reference levels on P1.1. Program will
// cycle through the on-chip comparator_A reference voltages with output on
// P1.1. Normal mode is LPM0, TA0_ISR will interrupt LPM0.
// ACLK = n/a, MCLK = SMCLK = default DCO
//
// MSP430G2x13/G2x53
// -----------------
// /|\| XIN|-
// | | |
// --|RST XOUT|-
// | |
// | P1.1/CA1|--> Vref
// | |
//
// D. Dang
// Texas Instruments Inc.
// December 2010
// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10
//******************************************************************************
#include <msp430.h>
void delay(void); // Software delay
int main (void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
CACTL2 = P2CA4; // CA1/P1.1 = +comp
CCTL0 = CCIE; // CCR0 interrupt enabled
TACTL = TASSEL_2 + ID_3 + MC_2; // SMCLK/8, cont-mode
_EINT(); // enable interrupts
while (1) // Loop
{
CACTL1 = 0x00; // No reference voltage
_BIS_SR(LPM0_bits); // Enter LPM0
CACTL1 = CAREF0 + CAON; // 0.25*Vcc, Comp. on
_BIS_SR(LPM0_bits); // Enter LPM0
CACTL1 = CAREF1 + CAON; // 0.5*Vcc, Comp. on
_BIS_SR(LPM0_bits); // Enter LPM0
CACTL1 = CAREF1 + CAREF0 + CAON; // 0.55V, Comp. on
_BIS_SR(LPM0_bits); // Enter LPM0
}
}
// Timer A0 interrupt service routine
#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
{
_BIC_SR_IRQ(LPM0_bits); // Clear LPM0 bits from 0(SR)
} |
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一只鸟敢站在脆弱的枝条上歇脚,它依仗的不是枝条不会断,而是自己有翅膀,会飞。
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