jim hamblen
Pushbutton counter demo showing switch contact bounce
main.cpp@0:996a0fc1fdea, 2011-09-20 (annotated)
- Committer:
- 4180_1
- Date:
- Tue Sep 20 13:59:06 2011 +0000
- Revision:
- 0:996a0fc1fdea
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| 4180_1 | 0:996a0fc1fdea | 1 | #include "mbed.h" |
| 4180_1 | 0:996a0fc1fdea | 2 | |
| 4180_1 | 0:996a0fc1fdea | 3 | DigitalOut myled(LED1); |
| 4180_1 | 0:996a0fc1fdea | 4 | DigitalOut myled2(LED2); |
| 4180_1 | 0:996a0fc1fdea | 5 | DigitalOut myled3(LED3); |
| 4180_1 | 0:996a0fc1fdea | 6 | DigitalOut myled4(LED4); |
| 4180_1 | 0:996a0fc1fdea | 7 | |
| 4180_1 | 0:996a0fc1fdea | 8 | DigitalIn pb(p8); |
| 4180_1 | 0:996a0fc1fdea | 9 | // SPST Pushbutton count demo using internal PullUp function |
| 4180_1 | 0:996a0fc1fdea | 10 | // no external PullUp resistor needed |
| 4180_1 | 0:996a0fc1fdea | 11 | // Pushbutton from P8 to GND. |
| 4180_1 | 0:996a0fc1fdea | 12 | // Demonstrates need for debounce - will sometimes count more than once per button hit |
| 4180_1 | 0:996a0fc1fdea | 13 | // This occurs on all switches due to mechanical contact bounce |
| 4180_1 | 0:996a0fc1fdea | 14 | int main() |
| 4180_1 | 0:996a0fc1fdea | 15 | { |
| 4180_1 | 0:996a0fc1fdea | 16 | int count=0; |
| 4180_1 | 0:996a0fc1fdea | 17 | int old_pb=1; |
| 4180_1 | 0:996a0fc1fdea | 18 | int new_pb; |
| 4180_1 | 0:996a0fc1fdea | 19 | // Use internal pullup for pushbutton |
| 4180_1 | 0:996a0fc1fdea | 20 | pb.mode(PullUp); |
| 4180_1 | 0:996a0fc1fdea | 21 | // Delay for initial pullup to take effect |
| 4180_1 | 0:996a0fc1fdea | 22 | wait(.001); |
| 4180_1 | 0:996a0fc1fdea | 23 | while(1) { |
| 4180_1 | 0:996a0fc1fdea | 24 | new_pb = pb; |
| 4180_1 | 0:996a0fc1fdea | 25 | if ((new_pb==0) && (old_pb==1)) count++; |
| 4180_1 | 0:996a0fc1fdea | 26 | myled4 = count & 0x01; |
| 4180_1 | 0:996a0fc1fdea | 27 | myled3 = (count & 0x02)>>1; |
| 4180_1 | 0:996a0fc1fdea | 28 | myled2 = (count & 0x04)>>2; |
| 4180_1 | 0:996a0fc1fdea | 29 | myled = (count & 0x08)>>3; |
| 4180_1 | 0:996a0fc1fdea | 30 | old_pb = new_pb; |
| 4180_1 | 0:996a0fc1fdea | 31 | } |
| 4180_1 | 0:996a0fc1fdea | 32 | } |