Sarang Kharche / Mbed OS digitalInPolling_sample

Solution to Polling Exercise

Fork of digitalInPolling_sample by William Marsh

main.cpp@3:914be74674bb, 2018-02-01 (annotated)

Committer:
Sarang
Date:
Thu Feb 01 17:19:35 2018 +0000
Revision:
3:914be74674bb
Parent:
2:cd1fe8c29793 
Final;

Who changed what in which revision?

UserRevisionLine numberNew 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
Sarang 3:914be74674bb 17 volatile int timez = 200 ;
Sarang 3:914be74674bb 18
WilliamMarshQMUL 0:a66a8cb0012c 19 enum buttonPos { up, down, bounce }; // Button positions
WilliamMarshQMUL 0:a66a8cb0012c 20 void polling() {
WilliamMarshQMUL 0:a66a8cb0012c 21 buttonPos pos = up ;
WilliamMarshQMUL 0:a66a8cb0012c 22 int bcounter = 0 ;
WilliamMarshQMUL 0:a66a8cb0012c 23 while (true) {
WilliamMarshQMUL 0:a66a8cb0012c 24 switch (pos) {
WilliamMarshQMUL 0:a66a8cb0012c 25 case up :
WilliamMarshQMUL 2:cd1fe8c29793 26 if (!b1.read()) { // now down
WilliamMarshQMUL 0:a66a8cb0012c 27 pressEvent = 1 ; // transition occurred
WilliamMarshQMUL 0:a66a8cb0012c 28 pos = down ;
WilliamMarshQMUL 0:a66a8cb0012c 29 }
WilliamMarshQMUL 0:a66a8cb0012c 30 break ;
WilliamMarshQMUL 0:a66a8cb0012c 31 case down :
WilliamMarshQMUL 2:cd1fe8c29793 32 if (b1 == 1) { // no longer down
WilliamMarshQMUL 0:a66a8cb0012c 33 bcounter = 3 ; // wait four cycles
WilliamMarshQMUL 0:a66a8cb0012c 34 pos = bounce ;
WilliamMarshQMUL 0:a66a8cb0012c 35 }
WilliamMarshQMUL 0:a66a8cb0012c 36 break ;
WilliamMarshQMUL 0:a66a8cb0012c 37 case bounce :
WilliamMarshQMUL 2:cd1fe8c29793 38 if (b1 == 0) { // down again - button has bounced
WilliamMarshQMUL 0:a66a8cb0012c 39 pos = down ; // no event
WilliamMarshQMUL 0:a66a8cb0012c 40 } else if (bcounter == 0) {
WilliamMarshQMUL 0:a66a8cb0012c 41 pos = up ; // delay passed - reset to up
WilliamMarshQMUL 0:a66a8cb0012c 42 } else {
WilliamMarshQMUL 0:a66a8cb0012c 43 bcounter-- ; // continue waiting
WilliamMarshQMUL 0:a66a8cb0012c 44 }
WilliamMarshQMUL 0:a66a8cb0012c 45 break ;
WilliamMarshQMUL 0:a66a8cb0012c 46 }
WilliamMarshQMUL 0:a66a8cb0012c 47 Thread::wait(30);
WilliamMarshQMUL 0:a66a8cb0012c 48 }
WilliamMarshQMUL 0:a66a8cb0012c 49 }
WilliamMarshQMUL 0:a66a8cb0012c 50
WilliamMarshQMUL 2:cd1fe8c29793 51 /* ---- Main function (default thread) ----
WilliamMarshQMUL 2:cd1fe8c29793 52 Note that if this thread completes, nothing else works
WilliamMarshQMUL 2:cd1fe8c29793 53 */
WilliamMarshQMUL 2:cd1fe8c29793 54 int main() {
WilliamMarshQMUL 2:cd1fe8c29793 55 led = 1 ; // Initially off
WilliamMarshQMUL 2:cd1fe8c29793 56 pollT.start(callback(polling));
WilliamMarshQMUL 2:cd1fe8c29793 57
WilliamMarshQMUL 0:a66a8cb0012c 58 while(true) {
Sarang 3:914be74674bb 59 led = !led ;
WilliamMarshQMUL 0:a66a8cb0012c 60 if (pressEvent) {
WilliamMarshQMUL 0:a66a8cb0012c 61 pressEvent = 0 ; // clear the event variable
Sarang 3:914be74674bb 62
Sarang 3:914be74674bb 63 if (timez<1000)
Sarang 3:914be74674bb 64 {
Sarang 3:914be74674bb 65 timez+=200;
Sarang 3:914be74674bb 66 }
Sarang 3:914be74674bb 67
Sarang 3:914be74674bb 68 else
Sarang 3:914be74674bb 69 {
Sarang 3:914be74674bb 70 timez=200;
Sarang 3:914be74674bb 71 }
WilliamMarshQMUL 0:a66a8cb0012c 72 }
Sarang 3:914be74674bb 73
Sarang 3:914be74674bb 74 Thread::wait(timez);
Sarang 3:914be74674bb 75
WilliamMarshQMUL 0:a66a8cb0012c 76 }
Sarang 3:914be74674bb 77 }
Sarang 3:914be74674bb 78