avnish aggarwal
/
Bootcamp-Pushbutton_Debounce_Interrupt
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Pushbutton_Debounce_Interrupt
by 
jim hamblen
main.cpp@0:cc87c48aa43c, 2011-09-20 (annotated)
- Committer:
- 4180_1
- Date:
- Tue Sep 20 14:06:28 2011 +0000
- Revision:
- 0:cc87c48aa43c
- Child:
- 1:d5bb7a2e46c2
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| 4180_1 | 0:cc87c48aa43c | 1 | #include "mbed.h" |
| 4180_1 | 0:cc87c48aa43c | 2 | #include "PinDetect.h" |
| 4180_1 | 0:cc87c48aa43c | 3 | // must import Cookbook PinDetct library into project |
| 4180_1 | 0:cc87c48aa43c | 4 | // URL: http://mbed.org/users/AjK/libraries/PinDetect/lkyxpw |
| 4180_1 | 0:cc87c48aa43c | 5 | |
| 4180_1 | 0:cc87c48aa43c | 6 | DigitalOut myled(LED1); |
| 4180_1 | 0:cc87c48aa43c | 7 | DigitalOut myled2(LED2); |
| 4180_1 | 0:cc87c48aa43c | 8 | DigitalOut myled3(LED3); |
| 4180_1 | 0:cc87c48aa43c | 9 | DigitalOut myled4(LED4); |
| 4180_1 | 0:cc87c48aa43c | 10 | |
| 4180_1 | 0:cc87c48aa43c | 11 | PinDetect pb(p8); |
| 4180_1 | 0:cc87c48aa43c | 12 | // SPST Pushbutton debounced count demo using interrupts and callback |
| 4180_1 | 0:cc87c48aa43c | 13 | // no external PullUp resistor needed |
| 4180_1 | 0:cc87c48aa43c | 14 | // Pushbutton from P8 to GND. |
| 4180_1 | 0:cc87c48aa43c | 15 | // A pb hit generates an interrupt and activates the callback function |
| 4180_1 | 0:cc87c48aa43c | 16 | // after the switch is debounced |
| 4180_1 | 0:cc87c48aa43c | 17 | |
| 4180_1 | 0:cc87c48aa43c | 18 | // Global count variable |
| 4180_1 | 0:cc87c48aa43c | 19 | int volatile count=0; |
| 4180_1 | 0:cc87c48aa43c | 20 | |
| 4180_1 | 0:cc87c48aa43c | 21 | // Callback routine is interrupt activated by a debounced pb hit |
| 4180_1 | 0:cc87c48aa43c | 22 | void pb_hit_callback (void) { |
| 4180_1 | 0:cc87c48aa43c | 23 | count++; |
| 4180_1 | 0:cc87c48aa43c | 24 | myled4 = count & 0x01; |
| 4180_1 | 0:cc87c48aa43c | 25 | myled3 = (count & 0x02)>>1; |
| 4180_1 | 0:cc87c48aa43c | 26 | myled2 = (count & 0x04)>>2; |
| 4180_1 | 0:cc87c48aa43c | 27 | } |
| 4180_1 | 0:cc87c48aa43c | 28 | int main() { |
| 4180_1 | 0:cc87c48aa43c | 29 | |
| 4180_1 | 0:cc87c48aa43c | 30 | // Use internal pullup for pushbutton |
| 4180_1 | 0:cc87c48aa43c | 31 | pb.mode(PullUp); |
| 4180_1 | 0:cc87c48aa43c | 32 | // Delay for initial pullup to take effect |
| 4180_1 | 0:cc87c48aa43c | 33 | wait(.01); |
| 4180_1 | 0:cc87c48aa43c | 34 | // Setup Interrupt callback function for a pb hit |
| 4180_1 | 0:cc87c48aa43c | 35 | pb.attach_deasserted(&pb_hit_callback); |
| 4180_1 | 0:cc87c48aa43c | 36 | // Start sampling pb input using interrupts |
| 4180_1 | 0:cc87c48aa43c | 37 | pb.setSampleFrequency(); |
| 4180_1 | 0:cc87c48aa43c | 38 | |
| 4180_1 | 0:cc87c48aa43c | 39 | //Blink myled in main routine forever while responding to pb changes |
| 4180_1 | 0:cc87c48aa43c | 40 | // via interrupts that activate the callback counter function |
| 4180_1 | 0:cc87c48aa43c | 41 | while (1) { |
| 4180_1 | 0:cc87c48aa43c | 42 | myled = !myled; |
| 4180_1 | 0:cc87c48aa43c | 43 | wait(.5); |
| 4180_1 | 0:cc87c48aa43c | 44 | } |
| 4180_1 | 0:cc87c48aa43c | 45 | |
| 4180_1 | 0:cc87c48aa43c | 46 | } |