关于MSP430的ADC中断相关问题

在进行MSP430ADC相关代码操作的时候，遇到一个百思不得其解的问题，我们按照要求设置好ADC通道，ADC中断，程序始终无法进入到ADC中断中去，本人一次又一次确认通道选择是否出错，中断是否设置，但是依然无法进入中断，经过试验和搜索，终于找到了问题所在。

MSP430的ADC12IE寄存器虽然是用来使能各个ADC中断的，但是在单通道转换模式下，无论你使用的是哪个ADC通道，ADC12IE对应的中断只能是0x01,对应的中断标志位为ADC12IFG0，并且只能在ADC12MEM0中读取ADC的值。下面给出一个单通道转换的实例：

#include "msp430x54x.h"unsigned int adc;void main(void){  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT  ADC12CTL0 = ADC12SHT02 + ADC12ON;         // Sampling time, ADC12 on  ADC12CTL1 = ADC12SHP;                     // Use sampling timer  ADC12IE = 0x01;                           // Enable interrupt  ADC12MCTL0 |= ADC12INCH_4;  __delay_cycles(100);  ADC12CTL0 |= ADC12ENC;  P6SEL |= 0x10;                            // P6.4 ADC option select  while (1)  {    ADC12CTL0 |= ADC12SC;                   // Start sampling/conversion     __bis_SR_register(LPM0_bits + GIE);     // LPM0, ADC12_ISR will force exit    __no_operation();                       // For debugger  }}#pragma vector = ADC12_VECTOR__interrupt void ADC12_ISR(void){  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:                                  // Vector  6:  ADC12IFG0    adc = ADC12MEM0;                        // Read ADC12MEM     __bic_SR_register_on_exit(LPM0_bits);   // Exit active CPU    break;  case  8: break;                           // Vector  8:  ADC12IFG1  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;   }}

在上面的事例中，我们使用的是MSP430的P6.4引脚，ADC通道4，因为使用的是单通道单次转换模式，对应的中断是ADC12IFG0，对应的值在ADC12MEM0中读取，对于单通道多次转换模式也适用。

对于序列通道转换模式，ADC12IE的值取决于使用的ADC通道，ADC的值也从对应通道的ADC12MEM中读取，下面是序列通道单次转换的实例

#include "msp430x54x.h"
volatile unsigned int results[4];           // Needs to be global in this example
                                            // Otherwise, the compiler removes it
                                            // because it is not used for anything.
void main(void)
{
  WDTCTL = WDTPW+WDTHOLD;                   // Stop watchdog timer
  P6SEL = 0x0F;                             // Enable A/D channel inputs
  ADC12CTL0 = ADC12ON+ADC12MSC+ADC12SHT0_2; // Turn on ADC12, set sampling time
  ADC12CTL1 = ADC12SHP+ADC12CONSEQ_1;       // Use sampling timer, single sequence
  ADC12MCTL0 = ADC12INCH_0;                 // ref+=AVcc, channel = A0
  ADC12MCTL1 = ADC12INCH_1;                 // ref+=AVcc, channel = A1
  ADC12MCTL2 = ADC12INCH_2;                 // ref+=AVcc, channel = A2
  ADC12MCTL3 = ADC12INCH_3+ADC12EOS;        // ref+=AVcc, channel = A3, end seq.
  ADC12IE = 0x08;                           // Enable ADC12IFG.3
  ADC12CTL0 |= ADC12ENC;                    // Enable conversions
  while(1)
  {
    ADC12CTL0 |= ADC12SC;                   // Start convn - software trigger
    __bis_SR_register(LPM4_bits + GIE);     // Enter LPM4, Enable interrupts
    __no_operation();                       // For debugger    
  }
}
#pragma vector=ADC12_VECTOR
__interrupt void ADC12ISR (void)
{
    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: break;                           // Vector  8:  ADC12IFG1
  case 10: break;                           // Vector 10:  ADC12IFG2
  case 12:                                  // Vector 12:  ADC12IFG3
    results[0] = ADC12MEM0;                 // Move results, IFG is cleared
    results[1] = ADC12MEM1;                 // Move results, IFG is cleared
    results[2] = ADC12MEM2;                 // Move results, IFG is cleared
    results[3] = ADC12MEM3;                 // Move results, IFG is cleared
    __bic_SR_register_on_exit(LPM4_bits);   // Exit active CPU, SET BREAKPOINT HERE  
  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; 
  }
}

上面的事例使用了ADC的0,1,2,3四个通道，因为ADC可以一次转换多个通道，所以只使能了通道3的中断。

ADC的配置顺序尽量与上述列举的顺序一致，否则有概率会读取失败，具体原因笔者没有去深究

以上事例均在MSP430F5xx/6xx上实测