使用EFM32 的ACMP（模拟比较器）对I/O口电压进行比较，并在边沿触发中断。
void VCMP_Initial(void)
{
/* Enable clocks required */
CMU_ClockEnable(cmuClock_GPIO, true);
CMU_ClockEnable(cmuClock_ACMP0, true);
const ACMP_Init_TypeDef acmp_init =
{
false, /* Full bias current*/
false, /* Half bias current */
7, /* Biasprog current configuration */
true, /* Enable interrupt for falling edge */
false, /* Enable interrupt for rising edge */
acmpWarmTime256, /* Warm-up time in clock cycles, >140 cycles for 10us with 14MHz */
acmpHysteresisLevel1, /* Hysteresis configuration */
0, /* Inactive comparator output value */
false, /* Enable low power mode */
(int)(2.5*63/3.5), /* Vdd reference scaling */
true, /* Enable ACMP */
};
/* Init and set ACMP channel */
ACMP_Init(ACMP0, &acmp_init);
ACMP_ChannelSet(ACMP0, acmpChannel2V5, acmpChannel0);
ACMP_IntEnable(ACMP0, ACMP_IEN_EDGE); /* Enable edge interrupt */
/* Wait for warmup */
while (!(ACMP0->STATUS & ACMP_STATUS_ACMPACT)) ;
/* Enable interrupts */
NVIC_ClearPendingIRQ(ACMP0_IRQn);
NVIC_EnableIRQ(ACMP0_IRQn);
}
extern char IsFallIntoWater;
void ACMP0_IRQHandler(void)
{
/* Clear interrupt flag */
ACMP0->IFC = ACMP_IFC_EDGE;
}
附找到比较完整的使用手册，主要有中断输出模式及IO输出模式