circuitpython/docs/library/pyb.ExtInt.rst

Ignoring revisions in .git-blame-ignore-revs. Click here to bypass and see the normal blame view.

115 lines
3.4 KiB
ReStructuredText
Raw Normal View History

.. currentmodule:: pyb
.. _pyb.ExtInt:
2014-10-31 18:21:37 -04:00
class ExtInt -- configure I/O pins to interrupt on external events
==================================================================
There are a total of 22 interrupt lines. 16 of these can come from GPIO pins
and the remaining 6 are from internal sources.
2016-07-31 19:52:00 -04:00
For lines 0 through 15, a given line can map to the corresponding line from an
arbitrary port. So line 0 can map to Px0 where x is A, B, C, ... and
line 1 can map to Px1 where x is A, B, C, ... ::
def callback(line):
print("line =", line)
Note: ExtInt will automatically configure the gpio line as an input. ::
extint = pyb.ExtInt(pin, pyb.ExtInt.IRQ_FALLING, pyb.Pin.PULL_UP, callback)
Now every time a falling edge is seen on the X1 pin, the callback will be
called. Caution: mechanical pushbuttons have "bounce" and pushing or
releasing a switch will often generate multiple edges.
See: http://www.eng.utah.edu/~cs5780/debouncing.pdf for a detailed
explanation, along with various techniques for debouncing.
Trying to register 2 callbacks onto the same pin will throw an exception.
If pin is passed as an integer, then it is assumed to map to one of the
2016-07-31 19:52:00 -04:00
internal interrupt sources, and must be in the range 16 through 22.
All other pin objects go through the pin mapper to come up with one of the
gpio pins. ::
extint = pyb.ExtInt(pin, mode, pull, callback)
Valid modes are pyb.ExtInt.IRQ_RISING, pyb.ExtInt.IRQ_FALLING,
pyb.ExtInt.IRQ_RISING_FALLING, pyb.ExtInt.EVT_RISING,
pyb.ExtInt.EVT_FALLING, and pyb.ExtInt.EVT_RISING_FALLING.
Only the IRQ_xxx modes have been tested. The EVT_xxx modes have
something to do with sleep mode and the WFE instruction.
Valid pull values are pyb.Pin.PULL_UP, pyb.Pin.PULL_DOWN, pyb.Pin.PULL_NONE.
There is also a C API, so that drivers which require EXTI interrupt lines
can also use this code. See extint.h for the available functions and
usrsw.h for an example of using this.
Constructors
------------
.. class:: ExtInt(pin, mode, pull, callback)
Create an ExtInt object:
- ``pin`` is the pin on which to enable the interrupt (can be a pin object or any valid pin name).
- ``mode`` can be one of:
- ``ExtInt.IRQ_RISING`` - trigger on a rising edge;
- ``ExtInt.IRQ_FALLING`` - trigger on a falling edge;
- ``ExtInt.IRQ_RISING_FALLING`` - trigger on a rising or falling edge.
- ``pull`` can be one of:
- ``pyb.Pin.PULL_NONE`` - no pull up or down resistors;
- ``pyb.Pin.PULL_UP`` - enable the pull-up resistor;
- ``pyb.Pin.PULL_DOWN`` - enable the pull-down resistor.
- ``callback`` is the function to call when the interrupt triggers. The
callback function must accept exactly 1 argument, which is the line that
triggered the interrupt.
Class methods
-------------
.. classmethod:: ExtInt.regs()
Dump the values of the EXTI registers.
Methods
-------
.. method:: ExtInt.disable()
Disable the interrupt associated with the ExtInt object.
This could be useful for debouncing.
.. method:: ExtInt.enable()
Enable a disabled interrupt.
.. method:: ExtInt.line()
Return the line number that the pin is mapped to.
.. method:: ExtInt.swint()
Trigger the callback from software.
Constants
---------
.. data:: ExtInt.IRQ_FALLING
interrupt on a falling edge
.. data:: ExtInt.IRQ_RISING
interrupt on a rising edge
.. data:: ExtInt.IRQ_RISING_FALLING
interrupt on a rising or falling edge