使用Arduino为多个开关作Debounce

西门庆33

当两个金属触点（Contact）关闭或打开时，它将会产生多个信号，我们称之为Bounce。Debounce是一个硬体设备或是软件，确保金属触点关闭或打开时，只有一个信号将会产生。

这里我们使用Arduino为多个开关作Debounce

Arduino Playground里有一个Bounce程序库，但是有限制

• 不能启用单晶片内部的上拉电阻（pull-up resistor），因此，每个开关必须连接一个外部上拉电阻
• 编写代码时，不能在setup内检测开关的状态。因此，当按下开关同时开机，将不能检测到开关的状态
• 使用多个开关时，编写代码会比较麻烦
  

Adafruit有一例子，可以完美解决以上问题。只需更改byte buttons[] = {4, 5, 6, 7, 8, 9} ，就可以使用很多开关了。

1. #define DEBOUNCE 10  // button debouncer, how many ms to debounce, 5+ ms is usually plenty
   
2. 
   
3. // here is where we define the buttons that we'll use. button "1" is the first, button "6" is the 6th, etc
   
4. byte buttons[] = {4, 5, 6, 7, 8, 9};
   
5. 
   
6. // This handy macro lets us determine how big the array up above is, by checking the size
   
7. #define NUMBUTTONS sizeof(buttons)
   
8. 
   
9. // we will track if a button is just pressed, just released, or 'currently pressed'
   
10. byte pressed[NUMBUTTONS], justpressed[NUMBUTTONS], justreleased[NUMBUTTONS];
    
11. 
    
12. void setup() {
    
13.   byte i;
    
14. 
    
15.   // set up serial port
    
16.   Serial.begin(9600);
    
17.   Serial.print("Button checker with ");
    
18.   Serial.print(NUMBUTTONS, DEC);
    
19.   Serial.println(" buttons");
    
20.   // pin13 LED
    
21.   pinMode(13, OUTPUT);
    
22. 
    
23.   // Make input & enable pull-up resistors on switch pins
    
24.   for (i=0; i< NUMBUTTONS; i++) {
    
25.     pinMode(buttons[i], INPUT);
    
26.     digitalWrite(buttons[i], HIGH);
    
27.   }
    
28. }
    
29. 
    
30. void check_switches()
    
31. {
    
32.   static byte previousstate[NUMBUTTONS];
    
33.   static byte currentstate[NUMBUTTONS];
    
34.   static long lasttime;
    
35.   byte index;
    
36.   if (millis() < lasttime) {
    
37.      lasttime = millis(); // we wrapped around, lets just try again
    
38.   }
    
39. 
    
40.   if ((lasttime + DEBOUNCE) > millis()) {
    
41.     return; // not enough time has passed to debounce
    
42.   }
    
43.   // ok we have waited DEBOUNCE milliseconds, lets reset the timer
    
44.   lasttime = millis();
    
45. 
    
46.   for (index = 0; index < NUMBUTTONS; index++) {
    
47.     justpressed[index] = 0;       // when we start, we clear out the "just" indicators
    
48.     justreleased[index] = 0;
    
49. 
    
50.     currentstate[index] = digitalRead(buttons[index]);   // read the button
    
51.     if (currentstate[index] == previousstate[index]) {
    
52.       if ((pressed[index] == LOW) && (currentstate[index] == LOW)) {
    
53.           // just pressed
    
54.           justpressed[index] = 1;
    
55.       }
    
56.       else if ((pressed[index] == HIGH) && (currentstate[index] == HIGH)) {
    
57.           // just released
    
58.           justreleased[index] = 1;
    
59.       }
    
60.       pressed[index] = !currentstate[index];  // remember, digital HIGH means NOT pressed
    
61.     }
    
62.     //Serial.println(pressed[index], DEC);
    
63.     previousstate[index] = currentstate[index];   // keep a running tally of the buttons
    
64.   }
    
65. }
    
66. 
    
67. void loop() {
    
68.   check_switches();      // when we check the switches we'll get the current state
    
69. 
    
70.   for (byte i = 0; i < NUMBUTTONS; i++) {
    
71.     if (justpressed[i]) {
    
72.       Serial.print(i, DEC);
    
73.       Serial.println(" Just pressed");
    
74.       // remember, check_switches() will CLEAR the 'just pressed' flag
    
75.     }
    
76.     if (justreleased[i]) {
    
77.       Serial.print(i, DEC);
    
78.       Serial.println(" Just released");
    
79.       // remember, check_switches() will CLEAR the 'just pressed' flag
    
80.     }
    
81.     if (pressed[i]) {
    
82.       Serial.print(i, DEC);
    
83.       Serial.println(" pressed");
    
84.       // is the button pressed down at this moment
    
85.     }
    
86.   }
    
87. }

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我稍为修改了上面例子，让按钮按下时，只产生一个信号。如果想再产生另一个信号，那就必须释放按钮，再按一下按钮。使用此方法来更改电子闹钟的时间，将是非常简单与方便。

1. #define DEBOUNCE 10  // button debouncer, how many ms to debounce, 5+ ms is usually plenty
   
2. 
   
3. // here is where we define the buttons that we'll use. button "1" is the first, button "6" is the 6th, etc
   
4. byte buttons[] = {4, 5, 6, 7, 8, 9};
   
5. 
   
6. // This handy macro lets us determine how big the array up above is, by checking the size
   
7. #define NUMBUTTONS sizeof(buttons)
   
8. 
   
9. // we will track if a button is just pressed, just released, or 'currently pressed'
   
10. byte pressed[NUMBUTTONS], justpressed[NUMBUTTONS], justreleased[NUMBUTTONS];
    
11. 
    
12. byte previous_keystate[NUMBUTTONS], current_keystate[NUMBUTTONS];
    
13. 
    
14. void setup() {
    
15.   byte i;
    
16.   // set up serial port
    
17.   Serial.begin(9600);
    
18.   Serial.print("Button checker with ");
    
19.   Serial.print(NUMBUTTONS, DEC);
    
20.   Serial.println(" buttons");
    
21.   // pin13 LED
    
22.   pinMode(13, OUTPUT);
    
23.   // Make input & enable pull-up resistors on switch pins
    
24.   for (i=0; i< NUMBUTTONS; i++) {
    
25.     pinMode(buttons[i], INPUT);
    
26.     digitalWrite(buttons[i], HIGH);
    
27.   }
    
28. }
    
29. 
    
30. void check_switches()
    
31. {
    
32.   static byte previousstate[NUMBUTTONS];
    
33.   static byte currentstate[NUMBUTTONS];
    
34.   static long lasttime;
    
35.   byte index;
    
36.   if (millis() < lasttime) {
    
37.     // we wrapped around, lets just try again
    
38.     lasttime = millis();
    
39.   }
    
40.   if ((lasttime + DEBOUNCE) > millis()) {
    
41.     // not enough time has passed to debounce
    
42.     return;
    
43.   }
    
44.   // ok we have waited DEBOUNCE milliseconds, lets reset the timer
    
45.   lasttime = millis();
    
46.   for (index = 0; index < NUMBUTTONS; index++) {
    
47.     justpressed[index] = 0;       // when we start, we clear out the "just" indicators
    
48.     justreleased[index] = 0;
    
49.     currentstate[index] = digitalRead(buttons[index]);   // read the button
    
50.     if (currentstate[index] == previousstate[index]) {
    
51.       if ((pressed[index] == LOW) && (currentstate[index] == LOW)) {
    
52.         // just pressed
    
53.         justpressed[index] = 1;
    
54.       }
    
55.       else if ((pressed[index] == HIGH) && (currentstate[index] == HIGH)) {
    
56.         justreleased[index] = 1; // just released
    
57.       }
    
58.       pressed[index] = !currentstate[index];  // remember, digital HIGH means NOT pressed
    
59.     }
    
60.     previousstate[index] = currentstate[index];   // keep a running tally of the buttons
    
61.   }
    
62. }
    
63. 
    
64. void loop() {
    
65.   check_switches();      // when we check the switches we'll get the current state
    
66.   for (byte i = 0; i < NUMBUTTONS; i++) {
    
67.     current_keystate[i]=justpressed[i];
    
68.     if (current_keystate[i] != previous_keystate[i]) {
    
69.       if (current_keystate[i]) execute_Justpressed(i);
    
70.     }
    
71.     previous_keystate[i]=current_keystate[i];
    
72.   }
    
73. }
    
74. 
    
75. void execute_Justpressed(byte thisButton_pressed) {
    
76.   Serial.print("You press this button: ");
    
77.   Serial.println(thisButton_pressed);   
    
78. }

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