我将AD参考电压设置为外部参考，Vreflo管脚接地，Vrefhi管脚接2.5V参考电压(我确定管脚电压是2.5V)。理论上AD输入管脚电压为2.5V时AD值会满，到达4095左右。但是测试发现此时AD值并没有达到4095，而只有3100左右。而我把输入电压调到3.3V时，AD值才满。貌似是AD仍然用的是内部3.3V参考电压，而我设置的外部参考无效。下面是我AD设置的程序，请大神们帮我看看哪里不对。
void MDG_InitAdc(void)
{
EALLOW;
/* Enable Clock */
SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1;
/* If the boot ROM code is bypassed during the debug process, the following function MUST be called */
(*Device_cal)();
/* Power Up */
AdcRegs.ADCCTL1.bit.ADCBGPWD = 1; // Power band gap : 0 = off; 1 = on 用外部参考时“带隙电压”应关闭？？？
AdcRegs.ADCCTL1.bit.ADCREFPWD = 1; // Power reference : 0 = 0ff; 1 = on
AdcRegs.ADCCTL1.bit.ADCPWDN = 1; // ADC core: 0 = power Down; 1 = power Up
AdcRegs.ADCCTL1.bit.ADCENABLE = 1; // Enable ADC: 0 = Disable; 1 = Enable
AdcRegs.ADCCTL1.bit.ADCREFSEL = 1; // Reference select: 0 = internal band gap; 1 = external reference
/* divide AD clock */
AdcRegs.ADCCTL2.bit.CLKDIV2EN = 1; // DIV2EN,DIV4EN: 00 = SYSCLK; 01 = SYSCLK; 10 = SYSCLK/2; 11 = SYSCLK/4
AdcRegs.ADCCTL2.bit.CLKDIV4EN = 1;
EDIS;
/* re-calibrates */
DELAY_US(1000); // Delay before converting ADC channels
AdcOffsetSelfCal(); // re-calibrates the ADC zero offset
/* Select channel */
EALLOW;
AdcRegs.ADCSOC0CTL.bit.CHSEL = 15; // SOC0 input channel :15 = B7(threshold)
AdcRegs.ADCSOC1CTL.bit.CHSEL = 9; // SOC1 input channel : 9 = B1(signal)
/* Set the ADC sample window to the desired value (Sample window = ACQPS + 1) */
AdcRegs.ADCSOC0CTL.bit.ACQPS = 6; // 6 + 1 = 7
AdcRegs.ADCSOC1CTL.bit.ACQPS = 6;
/* Select simultaneous or sequential mode */
AdcRegs.ADCSAMPLEMODE.bit.SIMULEN0 = 0; // SOC0/1: 0 = sequential; 1 = simultaneous
/* EOC0-EOC15 trigger source to ADCINTx */
AdcRegs.INTSEL1N2.bit.INT1SEL = 0; // EOC0 AD中断1由EOC0触发 EOC对应SOC
AdcRegs.INTSEL1N2.bit.INT2SEL = 1; // EOC1
/* Enabled ADCINTx */
AdcRegs.INTSEL1N2.bit.INT1E = 1; // 0 = Disable; 1 = Enable
AdcRegs.INTSEL1N2.bit.INT2E = 1;
/* Continuous sampling setting */
AdcRegs.INTSEL1N2.bit.INT1CONT = 1; // 1 = continue; 0 = pulse
AdcRegs.INTSEL1N2.bit.INT2CONT = 1;
/* ADCINTs trigger at end or begin of conversion */
AdcRegs.ADCCTL1.bit.INTPULSEPOS = 1; // 0:begin; 1:end
/* SOCx interrupt trigger select*/
AdcRegs.ADCINTSOCSEL1.bit.SOC0 = 0; // 0 = Trigger; 1 = ADCINT1; 2 = ADCINT2; 3 = Invalid
AdcRegs.ADCINTSOCSEL1.bit.SOC1 = 1; // ADCIN1 ADCINT1 will trigger SOCx.TRIGSEL field is ignored.
/* SOCx trigger source select. */
AdcRegs.ADCSOC0CTL.bit.TRIGSEL = 1; // TINT0
/* interrupt pulse control */
AdcRegs.ADCCTL1.bit.INTPULSEPOS = 1; // interrupt occurs at : 0 = begin; 1 = end
/* setting Interrupt */
PieVectTable.ADCINT2 = &MDG_ADCINT2_ISR; // vector relocation
PieCtrlRegs.PIEIFR1.bit.INTx1 = 0; // Clear ADCINT1 flags
PieCtrlRegs.PIEIFR1.bit.INTx2 = 0; // Clear ADCINT2 flags
PieCtrlRegs.PIEIER1.bit.INTx1 = 0; // ADCINT1 = INT1.1
PieCtrlRegs.PIEIER1.bit.INTx2 = 1; // ADCINT2 = INT1.2
PieCtrlRegs.PIEACK.bit.ACK1 = 1; // Enable ACK1.x
IFR &= ~(1 << (1 - 1)); // Clear flags
IER |= 1 << (1 - 1); // Enable INT1.x
EDIS;
}
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