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Implemented polling code to check button press and change speed of button flashing.
Fork of digitalInPolling_sample by
main.cpp@3:17c6a539bd7c, 2018-02-01 (annotated)
- Committer:
- natgovor
- Date:
- Thu Feb 01 12:24:02 2018 +0000
- Revision:
- 3:17c6a539bd7c
- Parent:
- 2:cd1fe8c29793
Implemented polling code to check button press and change the speed of button flashing.
Who changed what in which revision?
User | Revision | Line number | New contents of line |
---|---|---|---|
WilliamMarshQMUL | 0:a66a8cb0012c | 1 | #include "mbed.h" |
WilliamMarshQMUL | 0:a66a8cb0012c | 2 | |
WilliamMarshQMUL | 0:a66a8cb0012c | 3 | // Labs 2: Example program for polling an input |
WilliamMarshQMUL | 0:a66a8cb0012c | 4 | // -------------------------------------------- |
WilliamMarshQMUL | 0:a66a8cb0012c | 5 | // The program uses a thread to poll a digital input |
WilliamMarshQMUL | 0:a66a8cb0012c | 6 | // - The thread monitors the position of the button |
WilliamMarshQMUL | 0:a66a8cb0012c | 7 | // - When the button transitions up and down, a press event is signaled |
WilliamMarshQMUL | 0:a66a8cb0012c | 8 | // - Button bounce is guarded against |
WilliamMarshQMUL | 2:cd1fe8c29793 | 9 | // A second thread (the default one) checks for the press event and toggles the LED |
WilliamMarshQMUL | 0:a66a8cb0012c | 10 | |
WilliamMarshQMUL | 2:cd1fe8c29793 | 11 | DigitalIn b1(PTD0, PullUp); |
WilliamMarshQMUL | 2:cd1fe8c29793 | 12 | DigitalOut led(LED1); |
WilliamMarshQMUL | 0:a66a8cb0012c | 13 | |
WilliamMarshQMUL | 0:a66a8cb0012c | 14 | Thread pollT ; // thread to poll |
WilliamMarshQMUL | 0:a66a8cb0012c | 15 | volatile int pressEvent = 0 ; // Variabe set by the polling thread |
WilliamMarshQMUL | 0:a66a8cb0012c | 16 | |
WilliamMarshQMUL | 0:a66a8cb0012c | 17 | enum buttonPos { up, down, bounce }; // Button positions |
WilliamMarshQMUL | 0:a66a8cb0012c | 18 | void polling() { |
WilliamMarshQMUL | 0:a66a8cb0012c | 19 | buttonPos pos = up ; |
WilliamMarshQMUL | 0:a66a8cb0012c | 20 | int bcounter = 0 ; |
WilliamMarshQMUL | 0:a66a8cb0012c | 21 | while (true) { |
WilliamMarshQMUL | 0:a66a8cb0012c | 22 | switch (pos) { |
WilliamMarshQMUL | 0:a66a8cb0012c | 23 | case up : |
WilliamMarshQMUL | 2:cd1fe8c29793 | 24 | if (!b1.read()) { // now down |
WilliamMarshQMUL | 0:a66a8cb0012c | 25 | pressEvent = 1 ; // transition occurred |
WilliamMarshQMUL | 0:a66a8cb0012c | 26 | pos = down ; |
WilliamMarshQMUL | 0:a66a8cb0012c | 27 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 28 | break ; |
WilliamMarshQMUL | 0:a66a8cb0012c | 29 | case down : |
WilliamMarshQMUL | 2:cd1fe8c29793 | 30 | if (b1 == 1) { // no longer down |
WilliamMarshQMUL | 0:a66a8cb0012c | 31 | bcounter = 3 ; // wait four cycles |
WilliamMarshQMUL | 0:a66a8cb0012c | 32 | pos = bounce ; |
WilliamMarshQMUL | 0:a66a8cb0012c | 33 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 34 | break ; |
WilliamMarshQMUL | 0:a66a8cb0012c | 35 | case bounce : |
WilliamMarshQMUL | 2:cd1fe8c29793 | 36 | if (b1 == 0) { // down again - button has bounced |
WilliamMarshQMUL | 0:a66a8cb0012c | 37 | pos = down ; // no event |
WilliamMarshQMUL | 0:a66a8cb0012c | 38 | } else if (bcounter == 0) { |
WilliamMarshQMUL | 0:a66a8cb0012c | 39 | pos = up ; // delay passed - reset to up |
WilliamMarshQMUL | 0:a66a8cb0012c | 40 | } else { |
WilliamMarshQMUL | 0:a66a8cb0012c | 41 | bcounter-- ; // continue waiting |
WilliamMarshQMUL | 0:a66a8cb0012c | 42 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 43 | break ; |
WilliamMarshQMUL | 0:a66a8cb0012c | 44 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 45 | Thread::wait(30); |
WilliamMarshQMUL | 0:a66a8cb0012c | 46 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 47 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 48 | |
WilliamMarshQMUL | 2:cd1fe8c29793 | 49 | /* ---- Main function (default thread) ---- |
WilliamMarshQMUL | 2:cd1fe8c29793 | 50 | Note that if this thread completes, nothing else works |
WilliamMarshQMUL | 2:cd1fe8c29793 | 51 | */ |
natgovor | 3:17c6a539bd7c | 52 | enum states { flashing, timeToCheck }; // flsh thread states |
WilliamMarshQMUL | 2:cd1fe8c29793 | 53 | int main() { |
natgovor | 3:17c6a539bd7c | 54 | int speed = 200; |
natgovor | 3:17c6a539bd7c | 55 | states state = flashing; |
natgovor | 3:17c6a539bd7c | 56 | int cycleCounter = 0; |
natgovor | 3:17c6a539bd7c | 57 | led = 0; // LED is on by default |
natgovor | 3:17c6a539bd7c | 58 | |
WilliamMarshQMUL | 2:cd1fe8c29793 | 59 | pollT.start(callback(polling)); |
WilliamMarshQMUL | 2:cd1fe8c29793 | 60 | |
WilliamMarshQMUL | 0:a66a8cb0012c | 61 | while(true) { |
natgovor | 3:17c6a539bd7c | 62 | Thread::wait(100); |
natgovor | 3:17c6a539bd7c | 63 | cycleCounter++; |
natgovor | 3:17c6a539bd7c | 64 | |
natgovor | 3:17c6a539bd7c | 65 | if (cycleCounter == 1) { |
natgovor | 3:17c6a539bd7c | 66 | state = timeToCheck; |
WilliamMarshQMUL | 0:a66a8cb0012c | 67 | } |
natgovor | 3:17c6a539bd7c | 68 | |
natgovor | 3:17c6a539bd7c | 69 | switch (state) { |
natgovor | 3:17c6a539bd7c | 70 | case flashing: |
natgovor | 3:17c6a539bd7c | 71 | if (cycleCounter == speed / 100) { |
natgovor | 3:17c6a539bd7c | 72 | led = !led; |
natgovor | 3:17c6a539bd7c | 73 | cycleCounter = 0; |
natgovor | 3:17c6a539bd7c | 74 | } |
natgovor | 3:17c6a539bd7c | 75 | break; |
natgovor | 3:17c6a539bd7c | 76 | case timeToCheck: |
natgovor | 3:17c6a539bd7c | 77 | if (pressEvent) { |
natgovor | 3:17c6a539bd7c | 78 | cycleCounter = 0; |
natgovor | 3:17c6a539bd7c | 79 | pressEvent = 0 ; // clear the event variable |
natgovor | 3:17c6a539bd7c | 80 | if (speed < 1000) { |
natgovor | 3:17c6a539bd7c | 81 | speed = speed + 200; |
natgovor | 3:17c6a539bd7c | 82 | } else { |
natgovor | 3:17c6a539bd7c | 83 | speed = 200; |
natgovor | 3:17c6a539bd7c | 84 | } |
natgovor | 3:17c6a539bd7c | 85 | } |
natgovor | 3:17c6a539bd7c | 86 | state = flashing; |
natgovor | 3:17c6a539bd7c | 87 | break; |
natgovor | 3:17c6a539bd7c | 88 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 89 | } |
WilliamMarshQMUL | 0:a66a8cb0012c | 90 | } |