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.
DebouncedIn.cpp@0:672241227e0d, 2009-11-27 (annotated)
- Committer:
- chris
- Date:
- Fri Nov 27 16:05:32 2009 +0000
- Revision:
- 0:672241227e0d
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| chris | 0:672241227e0d | 1 | #include "DebouncedIn.h" |
| chris | 0:672241227e0d | 2 | #include "mbed.h" |
| chris | 0:672241227e0d | 3 | |
| chris | 0:672241227e0d | 4 | /* |
| chris | 0:672241227e0d | 5 | * Constructor |
| chris | 0:672241227e0d | 6 | */ |
| chris | 0:672241227e0d | 7 | DebouncedIn::DebouncedIn(PinName in) |
| chris | 0:672241227e0d | 8 | : _in(in) { |
| chris | 0:672241227e0d | 9 | |
| chris | 0:672241227e0d | 10 | // reset all the flags and counters |
| chris | 0:672241227e0d | 11 | _samples = 0; |
| chris | 0:672241227e0d | 12 | _output = 0; |
| chris | 0:672241227e0d | 13 | _output_last = 0; |
| chris | 0:672241227e0d | 14 | _rising_flag = 0; |
| chris | 0:672241227e0d | 15 | _falling_flag = 0; |
| chris | 0:672241227e0d | 16 | _state_counter = 0; |
| chris | 0:672241227e0d | 17 | |
| chris | 0:672241227e0d | 18 | // Attach ticker |
| chris | 0:672241227e0d | 19 | _ticker.attach(this, &DebouncedIn::_sample, 0.005); |
| chris | 0:672241227e0d | 20 | } |
| chris | 0:672241227e0d | 21 | |
| chris | 0:672241227e0d | 22 | void DebouncedIn::_sample() { |
| chris | 0:672241227e0d | 23 | |
| chris | 0:672241227e0d | 24 | // take a sample |
| chris | 0:672241227e0d | 25 | _samples = _samples >> 1; // shift left |
| chris | 0:672241227e0d | 26 | |
| chris | 0:672241227e0d | 27 | if (_in) { |
| chris | 0:672241227e0d | 28 | _samples |= 0x80; |
| chris | 0:672241227e0d | 29 | } |
| chris | 0:672241227e0d | 30 | |
| chris | 0:672241227e0d | 31 | // examine the sample window, look for steady state |
| chris | 0:672241227e0d | 32 | if (_samples == 0x00) { |
| chris | 0:672241227e0d | 33 | _output = 0; |
| chris | 0:672241227e0d | 34 | } |
| chris | 0:672241227e0d | 35 | else if (_samples == 0xFF) { |
| chris | 0:672241227e0d | 36 | _output = 1; |
| chris | 0:672241227e0d | 37 | } |
| chris | 0:672241227e0d | 38 | |
| chris | 0:672241227e0d | 39 | |
| chris | 0:672241227e0d | 40 | // Rising edge detection |
| chris | 0:672241227e0d | 41 | if ((_output == 1) && (_output_last == 0)) { |
| chris | 0:672241227e0d | 42 | _rising_flag++; |
| chris | 0:672241227e0d | 43 | _state_counter = 0; |
| chris | 0:672241227e0d | 44 | } |
| chris | 0:672241227e0d | 45 | |
| chris | 0:672241227e0d | 46 | // Falling edge detection |
| chris | 0:672241227e0d | 47 | else if ((_output == 0) && (_output_last == 1)) { |
| chris | 0:672241227e0d | 48 | _falling_flag++; |
| chris | 0:672241227e0d | 49 | _state_counter = 0; |
| chris | 0:672241227e0d | 50 | } |
| chris | 0:672241227e0d | 51 | |
| chris | 0:672241227e0d | 52 | // steady state |
| chris | 0:672241227e0d | 53 | else { |
| chris | 0:672241227e0d | 54 | _state_counter++; |
| chris | 0:672241227e0d | 55 | } |
| chris | 0:672241227e0d | 56 | |
| chris | 0:672241227e0d | 57 | // update the output |
| chris | 0:672241227e0d | 58 | _output_last = _output; |
| chris | 0:672241227e0d | 59 | |
| chris | 0:672241227e0d | 60 | } |
| chris | 0:672241227e0d | 61 | |
| chris | 0:672241227e0d | 62 | |
| chris | 0:672241227e0d | 63 | |
| chris | 0:672241227e0d | 64 | // return number of rising edges |
| chris | 0:672241227e0d | 65 | int DebouncedIn::rising(void) { |
| chris | 0:672241227e0d | 66 | int return_value = _rising_flag; |
| chris | 0:672241227e0d | 67 | _rising_flag = 0; |
| chris | 0:672241227e0d | 68 | return(return_value); |
| chris | 0:672241227e0d | 69 | } |
| chris | 0:672241227e0d | 70 | |
| chris | 0:672241227e0d | 71 | // return number of falling edges |
| chris | 0:672241227e0d | 72 | int DebouncedIn::falling(void) { |
| chris | 0:672241227e0d | 73 | int return_value = _falling_flag; |
| chris | 0:672241227e0d | 74 | _falling_flag = 0; |
| chris | 0:672241227e0d | 75 | return(return_value); |
| chris | 0:672241227e0d | 76 | } |
| chris | 0:672241227e0d | 77 | |
| chris | 0:672241227e0d | 78 | // return number of ticsk we've bene steady for |
| chris | 0:672241227e0d | 79 | int DebouncedIn::steady(void) { |
| chris | 0:672241227e0d | 80 | return(_state_counter); |
| chris | 0:672241227e0d | 81 | } |
| chris | 0:672241227e0d | 82 | |
| chris | 0:672241227e0d | 83 | // return the debounced status |
| chris | 0:672241227e0d | 84 | int DebouncedIn::read(void) { |
| chris | 0:672241227e0d | 85 | return(_output); |
| chris | 0:672241227e0d | 86 | } |
| chris | 0:672241227e0d | 87 | |
| chris | 0:672241227e0d | 88 | // shorthand for read() |
| chris | 0:672241227e0d | 89 | DebouncedIn::operator int() { |
| chris | 0:672241227e0d | 90 | return read(); |
| chris | 0:672241227e0d | 91 | } |
| chris | 0:672241227e0d | 92 | |
| chris | 0:672241227e0d | 93 |