Haozun Sun / Mbed OS digitalInPolling_hzsun

polling

main.cpp@5:6ea498e4d496, 2020-02-12 (annotated)

Committer:
hzsun
Date:
Wed Feb 12 19:42:16 2020 +0000
Revision:
5:6ea498e4d496
Parent:
4:82f7ccb294d3 
polling

Who changed what in which revision?

UserRevisionLine numberNew contents of line
WilliamMarshQMUL 0:a66a8cb0012c 1 #include "mbed.h"
WilliamMarshQMUL 0:a66a8cb0012c 2
hzsun 5:6ea498e4d496 3 // Labs 2: polling
WilliamMarshQMUL 0:a66a8cb0012c 4 // --------------------------------------------
WilliamMarshQMUL 0:a66a8cb0012c 5
hzsun 5:6ea498e4d496 6 DigitalIn b1(PTD0, PullUp); // initialize the button
hzsun 5:6ea498e4d496 7 DigitalOut led(LED1); // initialize the led
WilliamMarshQMUL 0:a66a8cb0012c 8
hzsun 5:6ea498e4d496 9 Thread pollT ; // thread to poll
hzsun 5:6ea498e4d496 10 volatile int pressEvent = 0 ; // Variabe set by the polling thread
hzsun 5:6ea498e4d496 11
WilliamMarshQMUL 0:a66a8cb0012c 12
hzsun 5:6ea498e4d496 13 enum buttonPos { up, down, bounce }; // Button positions
hzsun 5:6ea498e4d496 14 void polling() {
hzsun 5:6ea498e4d496 15 buttonPos pos = up ; //initialize the button position
hzsun 5:6ea498e4d496 16 int bcounter = 0 ; //initialize the counter
WilliamMarshQMUL 0:a66a8cb0012c 17 while (true) {
hzsun 5:6ea498e4d496 18 ThisThread::sleep_for(30) ; // poll every 30ms
WilliamMarshQMUL 0:a66a8cb0012c 19 switch (pos) {
WilliamMarshQMUL 0:a66a8cb0012c 20 case up :
hzsun 5:6ea498e4d496 21 if (!b1.read()) { // now down
hzsun 5:6ea498e4d496 22 pressEvent = 1 ; // transition occurred
hzsun 5:6ea498e4d496 23 pos = down ; // change to down position
WilliamMarshQMUL 0:a66a8cb0012c 24 }
WilliamMarshQMUL 0:a66a8cb0012c 25 break ;
WilliamMarshQMUL 0:a66a8cb0012c 26 case down :
hzsun 5:6ea498e4d496 27 if (b1 == 1) { // no longer down
hzsun 5:6ea498e4d496 28 bcounter = 3 ; // wait four cycles
hzsun 5:6ea498e4d496 29 pos = bounce ; //change to bounce position
WilliamMarshQMUL 0:a66a8cb0012c 30 }
WilliamMarshQMUL 0:a66a8cb0012c 31 break ;
WilliamMarshQMUL 0:a66a8cb0012c 32 case bounce :
hzsun 5:6ea498e4d496 33 if (b1 == 0) { // down again - button has bounced
hzsun 5:6ea498e4d496 34 pos = down ; // no event
WilliamMarshQMUL 0:a66a8cb0012c 35 } else if (bcounter == 0) {
hzsun 5:6ea498e4d496 36 pos = up ; // delay passed - reset to up
WilliamMarshQMUL 0:a66a8cb0012c 37 } else {
hzsun 5:6ea498e4d496 38 bcounter-- ; // continue waiting
WilliamMarshQMUL 0:a66a8cb0012c 39 }
WilliamMarshQMUL 0:a66a8cb0012c 40 break ;
WilliamMarshQMUL 0:a66a8cb0012c 41 }
WilliamMarshQMUL 0:a66a8cb0012c 42 }
WilliamMarshQMUL 0:a66a8cb0012c 43 }
WilliamMarshQMUL 0:a66a8cb0012c 44
hzsun 5:6ea498e4d496 45 /* ---- Main function (----
WilliamMarshQMUL 2:cd1fe8c29793 46 */
WilliamMarshQMUL 2:cd1fe8c29793 47 int main() {
hzsun 5:6ea498e4d496 48 led = 0 ; // Initially off
WilliamMarshQMUL 2:cd1fe8c29793 49 pollT.start(callback(polling));
hzsun 5:6ea498e4d496 50 int i=0; //create a counter for controling the speed of LED
hzsun 5:6ea498e4d496 51 int flashspeed[]={200, 400, 600, 800, 1000}; //input the value for chaging the speed of LED
WilliamMarshQMUL 0:a66a8cb0012c 52 while(true) {
WilliamMarshQMUL 0:a66a8cb0012c 53 if (pressEvent) {
hzsun 5:6ea498e4d496 54 pressEvent = 0 ; // clear the event variable
hzsun 5:6ea498e4d496 55 i++ ; // counter add one
hzsun 5:6ea498e4d496 56 if (i>4){ // when counter is bigger than four change back to zero
hzsun 5:6ea498e4d496 57 i=0;
hzsun 5:6ea498e4d496 58 }
WilliamMarshQMUL 0:a66a8cb0012c 59 }
hzsun 5:6ea498e4d496 60 led =!led; // led blinks
hzsun 5:6ea498e4d496 61 ThisThread::sleep_for(flashspeed[i]) ; // delay for 200ms 400ms 600ms 800ms 1s then come back to 200ms
WilliamMarshQMUL 0:a66a8cb0012c 62 }
WilliamMarshQMUL 0:a66a8cb0012c 63 }