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Diffstat (limited to 'docs/tutorial')
| -rw-r--r-- | docs/tutorial/debounce.rst | 37 | ||||
| -rw-r--r-- | docs/tutorial/index.rst | 1 |
2 files changed, 38 insertions, 0 deletions
diff --git a/docs/tutorial/debounce.rst b/docs/tutorial/debounce.rst new file mode 100644 index 0000000000..f730e1d340 --- /dev/null +++ b/docs/tutorial/debounce.rst @@ -0,0 +1,37 @@ +Debouncing a pin input +====================== + +A pin used as input from a switch or other mechanical device can have a lot +of noise on it, rapidly changing from low to high when the switch is first +pressed or released. This noise can be eliminated using a capacitor (a +debouncing circuit). It can also be eliminated using a simple function that +makes sure the value on the pin is stable. + +The following function does just this. It gets the current value of the given +pin, and then waits for the value to change. The new pin value must be stable +for a continuous 20ms for it to register the change. You can adjust this time +(to say 50ms) if you still have noise. :: + + import pyb + + def wait_pin_change(pin): + # wait for pin to change value + # it needs to be stable for a continuous 20ms + cur_value = pin.value() + active = 0 + while active < 20: + if pin.value() != cur_value: + active += 1 + else: + active = 0 + pyb.delay(1) + + +Use it something like this:: + + import pyb + + pin_x1 = pyb.Pin('X1', pyb.Pin.IN, pyb.Pin.PULL_DOWN) + while True: + wait_pin_change(pin_x1) + pyb.LED(4).toggle() diff --git a/docs/tutorial/index.rst b/docs/tutorial/index.rst index ed1137e1be..c134d0deb7 100644 --- a/docs/tutorial/index.rst +++ b/docs/tutorial/index.rst @@ -43,4 +43,5 @@ Tips, tricks and useful things to know :maxdepth: 1 :numbered: + debounce.rst pass_through.rst |