MSP430F5172 比较器B 不能动态切换为其他通道输入

HI

现在我要使用MSP430F5172的比较器B，对4个外部信号电平跟内部的参考电压进行比较判断，单独使用一个通道对外部电平信号进行比较都没有问题，

现在是问题是MCU只有一个比较器B，而我需要对4个外部电平进行判断，所以我想使用时间片来动态切换输入通道，验证了就是不行，输入通道配置为第一个后就不能配置为其他输入通道了，造成根本没办法检测到后面3个通道的输入变化。

我找了好多资料和例子，都是只使用一个输入通道的，如果说硬件上不支持多个通道进行切换，那为什么有CB0 到CB15 多达15个通道？？？

1.比较器B框图

2.原理图

3.部分代码

// MOTOR1_TOUCH   ---- CB15
// MOTOR2_TOUCH   ---- CB14
// MOTOR3_TOUCH   ---- CB13
// MOTOR4_TOUCH   ---- CB10
volatile uint8_t touched;         //Is the fader currently being touched?
volatile uint8_t index_port;
uint16_t time_count_1ms;

uint16_t time1_bak;
uint16_t time2_bak;
uint16_t time3_bak;
uint16_t time4_bak;

// Setup ComparatorB
void initCompare(void)
{
    CBCTL0 &=~(CBIPSEL_10+CBIPSEL_13+CBIPSEL_14+CBIPSEL_15);
    CBCTL3 &=~(BITA+BITD+BITE+BITF);

    CBCTL0 |= CBIPEN;// + CBIPSEL_15;// + CBIPSEL_13 + CBIPSEL_14 + CBIPSEL_15;
                                  // Enable V+, input channel CB0
    CBCTL1 |= CBPWRMD_1;          // normal power mode
    CBCTL2 |= CBRSEL;             // VREF is applied to -terminal

    //Vcb_refv = IN*(n+1)/32
    CBCTL2 |= CBRS_1+CBREF0_15;   // VREF0设为16/32*Vcc == 1.15v   3.3


    //CBCTL3 |= BITF;               // + BITD + BITE + BITF;
                                  // Input Buffer Disable @P3.7/CB10  @P3.3/CB13   @P3.2/CB14   @PJ.6/CB15

    __delay_cycles(7500);           // 延迟以待参考电压稳定

    CBINT &= ~(CBIFG + CBIIFG);   // Clear any errant interrupts
    //CBINT  |= CBIE;             // Enable CompB Interrupt on rising edge of CBIFG (CBIES=0) 0 ---> 1.15

    CBINT  |= CBIE + CBIES;       // Enable CompB Interrupt on falling edge of CBIFG (CBIES=1) 3.3 ---> 1.15
    CBCTL1 |= CBON;               // Turn On ComparatorB

    //
    index_port = 0;
}



// Comp_B ISR
#pragma vector=COMP_B_VECTOR
__interrupt void Comp_B_ISR (void)
{
    CBINT  &=~CBIFG;               // Clear Interrupt flag
    if(index_port == 0)
        return;

    if(index_port == 1){             // MOTOR1_TOUCH
        touched   |= 0x01;           // Detect do touch
        time1_bak  = time_count_1ms; // Record curent time
    }
    if(index_port == 2){             // MOTOR2_TOUCH
        touched   |= 0x02;           // Detect do touch
        time2_bak  = time_count_1ms; // Record curent time
    }
    if(index_port == 3){             // MOTOR3_TOUCH
        touched   |= 0x04;           // Detect do touch
        time3_bak  = time_count_1ms; // Record curent time
    }
    if(index_port == 4){             // MOTOR4_TOUCH
        touched   |= 0x08;           // Detect do touch
        time4_bak  = time_count_1ms; // Record curent time
    }
}


//Check to see if the fader is being touched
void checkTouch(void)
{
    if(time_count_1ms%1000 == 0){
        time_count_1ms++;
        index_port++;
        if(index_port>4)
            index_port = 1;
        CBCTL0 &=~(CBIPSEL_10+CBIPSEL_13+CBIPSEL_14+CBIPSEL_15);
        CBCTL3 &=~(BITA+BITD+BITE+BITF);
        if(index_port == 1){
            CBCTL0 |= CBIPSEL_15;
            CBCTL3 |= BITF;
        }else if(index_port == 2){
            CBCTL0 |= CBIPSEL_14;
            CBCTL3 |= BITE;
        }else if(index_port == 3){
            CBCTL0 |= CBIPSEL_13;
            CBCTL3 |= BITD;
        }else if(index_port == 4){
            CBCTL0 |= CBIPSEL_10;
            CBCTL3 |= BITA;
        }
    }

    //juge Touch 
    if(time_count_1ms > time1_bak + 20){ //timeout
        touched &=~0x01;
    }
    if(time_count_1ms > time2_bak + 20){
        touched &=~0x02;
    }
    if(time_count_1ms > time3_bak + 20){
        touched &=~0x04;
    }
    if(time_count_1ms > time4_bak + 20){
        touched &=~0x08;
    }

    printf("--touch--0x%d  index_port:%d\r\n",touched,index_port);
    
}


void main(void)
{
	WDTCTL = WDTPW | WDTHOLD;	// stop watchdog timer

	pmm_setVcoreUp(0x01);       // Vcore setting of at max 3 for 24MHz MCLK
	pmm_setVcoreUp(0x02);
	pmm_setVcoreUp(0x03);

    initPorts();                // Config all the GPIOS for low-power (output low)
    initClocks();               // Config clocks. MCLK=SMCLK=DCO=2*XT1=24MHz; ACLK=REFO=32kHz
	//....
    initCompare();
	//....
    initTimerA0();


    __enable_interrupt();




    while(1){


        checkTouch();
	}
}