diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/library/pyb.Pin.rst | 59 | ||||
| -rw-r--r-- | docs/tutorial/debounce.rst | 37 | ||||
| -rw-r--r-- | docs/tutorial/index.rst | 1 |
3 files changed, 69 insertions, 28 deletions
diff --git a/docs/library/pyb.Pin.rst b/docs/library/pyb.Pin.rst index 576268172d..010996acf4 100644 --- a/docs/library/pyb.Pin.rst +++ b/docs/library/pyb.Pin.rst @@ -55,6 +55,9 @@ an ordinal pin number: You can set ``pyb.Pin.debug(True)`` to get some debug information about how a particular object gets mapped to a pin. +When a pin has the ``Pin.PULL_UP`` or ``Pin.PULL_DOWN`` pull-mode enabled, +that pin has an effective 40k Ohm resistor pulling it to 3V3 or GND +respectively (except pin Y5 which has 11k Ohm resistors). Constructors ------------ @@ -62,7 +65,7 @@ Constructors .. class:: pyb.Pin(id, ...) Create a new Pin object associated with the id. If additional arguments are given, - they are used to initialise the pin. See ``init``. + they are used to initialise the pin. See :meth:`pin.init`. Class methods @@ -88,24 +91,6 @@ Class methods Methods ------- -.. method:: pin.__str__() - - Return a string describing the pin object. - -.. method:: pin.af() - - Returns the currently configured alternate-function of the pin. The - integer returned will match one of the allowed constants for the af - argument to the init function. - -.. method:: pin.gpio() - - Returns the base address of the GPIO block associated with this pin. - -.. method:: pin.high() - - Set the pin to a high logic level. - .. method:: pin.init(mode, pull=Pin.PULL_NONE, af=-1) Initialise the pin: @@ -126,10 +111,37 @@ Methods Returns: ``None``. +.. method:: pin.high() + + Set the pin to a high logic level. + .. method:: pin.low() Set the pin to a low logic level. +.. method:: pin.value([value]) + + Get or set the digital logic level of the pin: + + - With no argument, return 0 or 1 depending on the logic level of the pin. + - With ``value`` given, set the logic level of the pin. ``value`` can be + anything that converts to a boolean. If it converts to ``True``, the pin + is set high, otherwise it is set low. + +.. method:: pin.__str__() + + Return a string describing the pin object. + +.. method:: pin.af() + + Returns the currently configured alternate-function of the pin. The + integer returned will match one of the allowed constants for the af + argument to the init function. + +.. method:: pin.gpio() + + Returns the base address of the GPIO block associated with this pin. + .. method:: pin.mode() Returns the currently configured mode of the pin. The integer returned @@ -158,15 +170,6 @@ Methods will match one of the allowed constants for the pull argument to the init function. -.. method:: pin.value([value]) - - Get or set the digital logic level of the pin: - - - With no argument, return 0 or 1 depending on the logic level of the pin. - - With ``value`` given, set the logic level of the pin. ``value`` can be - anything that converts to a boolean. If it converts to ``True``, the pin - is set high, otherwise it is set low. - Constants --------- 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 |