msp430f5529 adc12 检测电压范围问题

只看该作者 · 2011-11-22 15:51

在AD检测时, 当引脚的电压低于参考电压的一半时,检测值一直是参考值的一半,比如用的2.5的内部参考电压,当电压低于1.25V时检测的电压一直是1.25;
下面是MSP430的AD部分代码，麻烦查看下是否有问题？
ADC初始化
void luce_drv_msp_adc_init(void)
{
  /* Enable A/D channel A1 A3*/
  P6SEL |= (BIT1 | BIT3);

  /*Reset REFMSTR to hand over control to ADC12_A ref control registers*/
  REFCTL0 &= ~REFMSTR;

  /* Turn on ADC12, set sampling time*/
  ADC12CTL0 = ADC12ON+ADC12SHT0_8+ADC12MSC+ADC12REFON+ADC12REF2_5V;

  /* set multiple sample conversion*/

  /* Use sampling timer,slecet smclk set mode*/
  ADC12CTL1 = ADC12SHP+ADC12SSEL_3+ADC12CONSEQ_3;

  /*  VR+ = VREF+ and VR. = AVSS, channel = A1*/
  ADC12MCTL0 = ADC12SREF_1+ADC12INCH_1;

  /*  VR+ = VREF+ and VR. = AVSS, channel = A3, end seq. */
  ADC12MCTL1 = ADC12SREF_1+ADC12INCH_3+ADC12EOS;

  /* Enable ADC12IFG.1*/
  //ADC12IE = 0x02;

/* Enable conversions*/
  //ADC12CTL0 |= ADC12ENC;

/* Start conversion*/
  //ADC12CTL0 |= ADC12SC;
}

ADC使能
void luce_drv_msp_adc_enable(void)
{
   /* Enable ADC12IFG.1*/
   ADC12IE = 0x02;

   /* Enable conversions*/
   ADC12CTL0 |= ADC12ENC;

   /* Start conversion*/
   ADC12CTL0 |= ADC12SC;

}

ADC中断连续取8次值取平均值

#pragma vector=ADC12_VECTOR
__interrupt void ADC12ISR (void)
{
  static unsigned char index = 0;

  switch(__even_in_range(ADC12IV,34))
  {
  case  0: break;                         /* Vector  0:  No interrupt*/
  case  2: break;                         /* Vector  2:  ADC overflow*/
  case  4: break;                         /* Vector  4:  ADC timing overflow*/
  case  6: break;                         /* Vector  6:  ADC12IFG0*/
  case  8:                               /* Vector  8:  ADC12IFG1*/
uiBattVoltResults[index] = ADC12MEM0;          /* Move results*/
uiD5VSBVoltResults[index] = ADC12MEM1;
index++;                               /* Increment results index, modulo; Set Breakpoint1 here*/

if (index >= 8)                         /*8次检测完后清中断，停止ADC，置完成标志*/
{
   index = 0;
   ADC12IE = 0x00;
   ADC12IFG = 0x00;
   ADC12CTL0 &= ~( ADC12ENC | ADC12SC );                   /* Disable conversions & Stop conversion*/
   ucBattCheckFlag = LUCE_DRV_MSP_ADC_CHECKED;
}
break;

  case 10: break;                         /* Vector 10:  ADC12IFG2*/
  case 12: break;                         /* Vector 12:  ADC12IFG3*/
  case 14: break;                         /* Vector 14:  ADC12IFG4*/
  case 16: break;                         /* Vector 16:  ADC12IFG5*/
  case 18: break;                         /* Vector 18:  ADC12IFG6*/
  case 20: break;                         /* Vector 20:  ADC12IFG7*/
  case 22: break;                         /* Vector 22:  ADC12IFG8*/
  case 24: break;                         /* Vector 24:  ADC12IFG9*/
  case 26: break;                         /* Vector 26:  ADC12IFG10*/
  case 28: break;                         /* Vector 28:  ADC12IFG11*/
  case 30: break;                         /* Vector 30:  ADC12IFG12*/
  case 32: break;                         /* Vector 32:  ADC12IFG13*/
  case 34: break;                         /* Vector 34:  ADC12IFG14*/
  default: break;
  }
}

/*计算电池的平均电压值*/
for( ucIndex=0; ucIndex < Num_of_Results; ucIndex++ )
{
   uiBattNowVolt+= uiBattVoltResults[ucIndex];
   uiD5VSBNowVolt+= uiD5VSBVoltResults[ucIndex];
   luce_drv_msp_debug_printf("ADC uiBattVoltResults=0x", uiBattVoltResults[ucIndex]);
}

g_uiBattVoltValue  = (((unsigned long)( uiBattNowVolt/8)*ADC_REFER_VOLTAGE)/0xFFF)*ADC_BATT_VOLTAGE_MULT;
g_uiD5VSBVoltValue = (((unsigned long)( uiD5VSBNowVolt/8)*ADC_REFER_VOLTAGE)/0xFFF)*ADC_5VSB_VOLTAGE_MULT;

ADC_BATT_VOLTAGE_MULT  为11分压倍数
ADC_REFER_VOLTAGE  为参考电压现在值为2.43V

当电压低于13.78V时测的值一直是 13.78 uiBattNowVolt/8=0x0840