Diff: main.cpp

Revision:

0:f1c27b98a650

Child:

1:1ce199c334c2

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon Mar 09 18:23:33 2020 +0000
@@ -0,0 +1,69 @@
+#include "mbed.h"
+
+// Sample answer for lab 2
+// -----------------------
+//   Poll button
+//   Vary period of flashing LED
+
+DigitalIn button(PTD0, PullUp);
+DigitalOut led(LED_RED);
+
+Thread pollT ; // thread to poll
+Thread flashT ; // thread to flash light
+volatile int event = 0 ;
+
+enum switchPos { up, down, bounce };
+void polling() {
+    switchPos pos = up ;
+    int bcounter = 0 ;
+    while (true) {
+        switch (pos) {
+            case up :
+                if (button == 1) {
+                    event = 1 ;  // transition occurred
+                    pos = down ;
+                }
+                break ;
+            case down : 
+                if (button == 0) {
+                    bcounter = 3 ; // wait four cycles
+                    pos = bounce ;
+                }
+                break ;
+            case bounce :
+                if (button == 1) { // button has bounced
+                    pos = down ;     // no event
+                } else if (bcounter == 0) {
+                    pos = up ;
+                } else {
+                    bcounter-- ;
+                }
+                break ;
+        }
+        ThisThread::sleep_for(100) ; // delay for 100ms 
+    }
+}
+
+// Main thread
+//   Start polling thread
+//   Flash light with a period that varies with each button press 
+int main()
+{
+    pollT.start(&polling) ; // start the polling thread running 
+    int delay = 1 ; // range 1, 2, 3, 4, 5
+    int counter = 0 ; // counter for cycles since last flash
+    while(true) {
+        counter++ ; // increment the counter
+        if (event) {
+            delay = (delay % 5) + 1 ;
+            event = 0 ; // clear the event
+        }
+        if (counter >= 2 * delay) { // 2, 4, 6, 8, 10
+            led = !led ;
+            counter = 0 ;
+        }
+        ThisThread::sleep_for(100) ; // delay for 100ms 
+    }
+
+
+}
\ No newline at end of file