Revision 1:e84a51c98d75, committed 2017-10-23

Comitter:

noutram

Date:

Mon Oct 23 09:47:16 2017 +0000

Parent:

0:397b84c74d17

Child:

2:4cf6f5cba257

Commit message:

Tidy up and reduce latency

Changed in this revision

--- a/SWPoll.hpp	Mon Oct 23 09:37:46 2017 +0000
+++ b/SWPoll.hpp	Mon Oct 23 09:47:16 2017 +0000
@@ -3,23 +3,27 @@
 class SWPoll {
 private:
     enum State {LOW, LOW_DEBOUNCE, HIGH, HIGH_DEBOUNCE};
-    State state;
-    DigitalIn& sw;
-    DigitalOut& led;
-    Timer t;    
+    State state;        // Internal state
+    DigitalIn& sw;      // These are references (aliases) and MUST be initialised
+    DigitalOut& led;    // ""
+    Timer t;            // Each instance has it's own timer, so this is is finite
     
 public:
+    //Constructor - MUST be given two parameters (for the switch and led) BY REFERENCE
     SWPoll(DigitalIn& gpioIn, DigitalOut& gpioOut) : sw(gpioIn), led(gpioOut) {
         state = LOW;
         t.reset();
         led = 0;
     }    
+    //Destructor - should the instance go out of scope, this is called
     ~SWPoll() {
         //Shut down
         t.stop();
         t.reset();
         led = 0;   
     }
+    //The public API - poll the switches
+    //Bascially, a mealy machine - uses a timer to manage switch bounce
     void poll() {
         switch (state) 
         {
@@ -42,8 +46,9 @@
         
         case HIGH:
             if (sw == 0) {
+                led = !led; //Toggle output on state transition  
                 state = HIGH_DEBOUNCE;
-                t.reset();
+                t.reset(); //(purely defensive)
                 t.start();
             }
             break;
@@ -52,7 +57,6 @@
                 state = LOW;
                 t.stop();
                 t.reset();  
-                led = !led; //Toggle output on state transition  
             }
             break;            
          default:

--- a/main.cpp	Mon Oct 23 09:37:46 2017 +0000
+++ b/main.cpp	Mon Oct 23 09:47:16 2017 +0000
@@ -22,7 +22,7 @@
 SWPoll switch1(sw1, red_led);
 SWPoll switch2(sw2, green_led);
 
-
+//LOOK AT SWPoll.hpp for the definition of the SWPoll class
 
 int main() {
     
@@ -45,38 +45,3 @@
 }
 
 
-//Thread 1  - polling sw1 and controlling the red LED
-void task1()
-{
-    //Loop forever
-    while(1) {
-        //Spin on sw1
-        while (sw1 == RELEASED) {};
-        //Allow short delay for switch bounce
-        Thread::wait(200);
-        //Spin again on sw1
-        while (sw1 == PRESSED) {};    
-        //Toggle LED
-        red_led = !red_led;
-        //Again, wait for switch bounce
-        Thread::wait(200);
-    }    
-}
-
-//Thread 2  - polling sw2 and controlling the green LED
-void task2()
-{
-    //Loop forever
-    while(1) {
-        //Spin on sw2
-        while (sw2 == RELEASED) {};
-        //Allow short delay for switch bounce
-        Thread::wait(200);
-        //Spin again on sw2
-        while (sw2 == PRESSED) {};    
-        //Toggle LED
-        green_led = !green_led;
-        //Again, wait for switch bounce
-        Thread::wait(200);
-    }    
-}