msp430f2618使用pwm的衰落LED

Question

我想在C中编写代码以淡入使用PWM和MSP430f2618的板外LED。我可以让LED打开，但它保持全部亮度。我正在尝试读取频率值数组，并根据频率值淡入LED。

int main(void) 
{ 
    WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer 
    int array_size = 0, i = 0, delay = 0; 
    double frequency[50] = {0.0}; 

    array_size = sizeof(frequency); 

    frequency [0] = 60.0; 

    for (i = 1; i < array_size; i++) 
    { 
     if (frequency[i - 1] < 61) 
     { 
      frequency[i] = frequency[i-1] + 0.1; 
     } 
     else 
     { 
      frequency[i] = 60.0; 
     } 
    } 

    P4OUT &= 0; 
    P4DIR |= (BIT1 + BIT2); //P4.1 and P4.2 output 
    P4SEL &= ~(BIT1 + BIT2); //P4.1 and P4.2 TBx options, timer select 
    TBCCR0 = 512-1; 

    TBCCTL1 = OUTMOD_7; 
    TBCCTL2 = OUTMOD_7; 

    for (i = 0; i < array_size; i++) 
    { 
     P4OUT &= 0; 
     if ((frequency[i] < 60.2) && (frequency[i] >=60.0)) 
     { 
      //TBCCR1 = 3200; 
      TBCCR1 = 384; 
     } 

     else if ((frequency[i] < 60.4) && (frequency[i] >=60.2)) 
     { 
      //TBCCR1 = 2560; 
      TBCCR1 = 256; 
     } 

     else if ((frequency[i] < 60.6) && (frequency[i] >=60.4)) 
     { 
      //TBCCR1 = 1920; 
      TBCCR1 = 128; 
     } 

     else if ((frequency[i] < 60.8) && (frequency[i] >=60.6)) 
     { 
      //TBCCR1 = 1280; 
      TBCCR1 = 64; 
     } 

     else if ((frequency[i] < 61) && (frequency[i] >=60.8)) 
     { 
      //TBCCR1 = 640; 
      TBCCR1 = 32; 
     } 

     else 
     { 
      TBCCR2 = 512; 
     } 

     P4OUT ^= BIT1; 
     for (delay = 0; delay < 32000; delay++); 

    } 
    TBCTL = TBSSEL_2 + MC_1;     // ACLK, up mode 



    __bis_SR_register(LPM0_bits);    // Enter LPM3 
    return 0; 
} 

Answer 1

定时器只有在通过设置MC字段启动之后才会运行。初始化必须在开始时完成。