Revision 0:e2ba40ab11e8, committed 2016-05-24

Comitter:

janhavi

Date:

Tue May 24 08:56:29 2016 +0000

Commit message:

Simple debouncing library use example

Changed in this revision

diff -r 000000000000 -r e2ba40ab11e8 DebouncedIn.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DebouncedIn.cpp	Tue May 24 08:56:29 2016 +0000
@@ -0,0 +1,93 @@
+#include "DebouncedIn.h"
+#include "mbed.h"
+
+/*
+ * Constructor
+ */
+DebouncedIn::DebouncedIn(PinName in) 
+    : _in(in) {    
+        
+    // reset all the flags and counters    
+    _samples = 0;
+    _output = 0;
+    _output_last = 0;
+    _rising_flag = 0;
+    _falling_flag = 0;
+    _state_counter = 0;
+    
+    // Attach ticker
+    _ticker.attach(this, &DebouncedIn::_sample, 0.005);     
+}
+  
+void DebouncedIn::_sample() {
+
+    // take a sample
+    _samples = _samples >> 1; // shift left
+      
+    if (_in) {
+        _samples |= 0x80;
+    }  
+      
+    // examine the sample window, look for steady state
+    if (_samples == 0x00) {
+        _output = 0;
+    } 
+    else if (_samples == 0xFF) {
+        _output = 1;
+    }
+
+
+    // Rising edge detection
+    if ((_output == 1) && (_output_last == 0)) {
+        _rising_flag++;
+        _state_counter = 0;
+    }
+
+    // Falling edge detection
+    else if ((_output == 0) && (_output_last == 1)) {
+        _falling_flag++;
+        _state_counter = 0;
+    }
+    
+    // steady state
+    else {
+        _state_counter++;
+    }
+    
+   // update the output
+    _output_last = _output;
+    
+}
+
+
+
+// return number of rising edges
+int DebouncedIn::rising(void) {
+    int return_value = _rising_flag; 
+    _rising_flag = 0;
+    return(return_value);
+}
+
+// return number of falling edges
+int DebouncedIn::falling(void) {
+    int return_value = _falling_flag; 
+    _falling_flag = 0;
+    return(return_value);
+}
+
+// return number of ticsk we've bene steady for
+int DebouncedIn::steady(void) {
+return(_state_counter);
+}
+
+// return the debounced status
+int DebouncedIn::read(void) {
+    return(_output);
+}
+
+// shorthand for read()
+DebouncedIn::operator int() {
+    return read();
+}
+
+

diff -r 000000000000 -r e2ba40ab11e8 DebouncedIn.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DebouncedIn.h	Tue May 24 08:56:29 2016 +0000
@@ -0,0 +1,31 @@
+#include "mbed.h"
+
+    class DebouncedIn {
+        public:      
+             DebouncedIn(PinName in);
+
+             int read (void);
+             operator int();
+              
+             int rising(void);
+             int falling(void);
+             int steady(void);
+              
+        private :    
+               // objects
+               DigitalIn _in;    
+               Ticker _ticker;
+
+               // function to take a sample, and update flags
+               void _sample(void);
+
+               // counters and flags
+               int _samples;
+               int _output;
+               int _output_last;
+               int _rising_flag;
+               int _falling_flag;
+               int _state_counter;
+
+    };
+    
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