Chris Styles
This class carries out software debouncing of Digitial in, and provides some method to look at details such as how many debounced rising and falling there have been, and how long the input has been in its current stable state.
Revision 0:672241227e0d, committed 2009-11-27
- Comitter:
- chris
- Date:
- Fri Nov 27 16:05:32 2009 +0000
- Commit message:
Changed in this revision
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/DebouncedIn.cpp Fri Nov 27 16:05:32 2009 +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();
+}
+
+
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/DebouncedIn.h Fri Nov 27 16:05:32 2009 +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;
+
+ };
+
\ No newline at end of file
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Fri Nov 27 16:05:32 2009 +0000
@@ -0,0 +1,16 @@
+#include "mbed.h"
+#include "DebouncedIn.h"
+
+
+DigitalOut led(LED1);
+DebouncedIn button(p21);
+
+int main() {
+
+ while(1) {
+ if (button.rising()) {
+ led = !led;
+ }
+ }
+
+}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed.bld Fri Nov 27 16:05:32 2009 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/mbed_official/code/mbed/builds/20a79241b4a0