MSP430 LaunchPad |分配双击按钮

Question

我正在使用MSP-EXP430F5529LP。我已经可以用以下命令闪烁红色的led了。

#pragma vector=TIMER2_A0_VECTOR
__interrupt void Timer_A2(void)
{
    P1OUT ^= 0x01;
}

和

    TA0CCR0 = 25000;
    TA0CCTL0 |= CCIE;
    TA0CTL |= TASSEL_2 | ID_3 | MC_1 | TACLR;

我真的需要一些帮助，使双击检查

#pragma vector=PORT1_VECTOR

因此，我可以将它与单击区分开来。我只想使用简单的if在那里，并做一些基于单击或双击的工作人员。

Answer 1

通过使用计时器硬件闪烁LED的代码已经是检测双击按钮的一个很好的起点。我建议使用计时器来实现去抖动功能的基本功能，这是简单的向上/向下计数器，处理一些事件，如按钮输入。

按钮的问题是它们很嘈杂。如果您以足够快的速度从按钮采样MSP430的输入引脚，您会发现对于一个简单的按住事件，它会多次切换。松开按钮也会产生噪音。因此，您可以预期的双按事件的噪音很大。可以创建外部硬件电路来过滤印刷机的噪声部分，但软件成本较低，因此大多数实现都采用这种方法。

去抖动功能背后的思想是使用计时器来测量来自按钮输入的事件，以处理噪声。这里是检测单键按下的起点。这可以很容易地修改为双(或三)压力机！

// Define button status and the button variable
typedef enum {BUTTON_STATUS_NOTPRESSED, BUTTON_STATUS_HOLDING, BUTTON_STATUS_RELEASED} button_status_t;
button_status_t button = BUTTON_STATUS_NOTPRESSED;

// Define button state values (if inverted then swap the values, assume input at bit 1)
typedef enum {BUTTON_STATE_NOTPRESSED = 0, BUTTON_STATE_PRESSED = BIT1} button_state_t;

// Setup timer hardware for 1 ms ticks
TA0CCR0 = 125;
TA0CCTL0 = CCIE;
TA0CTL = TASSEL_2 | ID_3 | MC_1 | TACLR;

// Process the button events for every timer tick
#pragma vector=TIMER2_A0_VECTOR
__interrupt void Timer_A2(void) // Better name would be Timer_A0_2_ISR
{
  // Local variable for counting ticks when button is pressed
  // Assume nobody will ever hold the button for 2^32 ticks long!
  static uint32_t counter = 0;
  
  // Constant for measuring how long (ms) the button must be held
  // Adjust this value to feel right for a single button press
  const uint32_t BUTTON_PRESSED_THRES = 50;
  
  // Check status of button, assume P2.1 input for the button
  // Note once the button enters release status, other code must change back to not pressed
  switch (button)
  {
    case BUTTON_STATUS_NOTPRESSED:
      // Increment if pressed, else reset the count
      // This will filter out the noise when starting to press
      if ((P2IN & BIT1) == BUTTON_STATE_PRESSED) counter += 1;
      else counter = 0;
      if (counter > BUTTON_PRESSED_THRES) button = BUTTON_STATUS_HOLDING;
      break;
    
    case BUTTON_STATUS_HOLDING:
      // Decrement if not pressed, else set the count to threshold
      // This will filter out the noise when starting to release
      if ((P2IN & BIT1) == BUTTON_STATE_NOTPRESSED) counter -= 1;
      else counter = BUTTON_PRESSED_THRES;
      if (counter == 0) button = BUTTON_STATUS_RELEASED;
      break;
  }
}

// Your other code to detect when the button has been pressed and release
if (button == BUTTON_STATUS_RELEASED)
{
    // do something
    // Must reset after detecting button has been release
    button = BUTTON_STATUS_NOTPRESSED;
}