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diff --git a/source/external-interrupts.rst b/source/external-interrupts.rst deleted file mode 100644 index 209d5af..0000000 --- a/source/external-interrupts.rst +++ /dev/null @@ -1,68 +0,0 @@ -.. highlight:: cpp - -.. _external-interrupts: - -External Interrupts -=================== - -External interrupts can be used to make a voltage change on a -:ref:`pin <gpio>` (the pin going from :ref:`LOW <lang-constants-low>` -to :ref:`HIGH <lang-constants-high>`, or vice-versa) to cause a -function to be called. This can be used to avoid checking for changes -on a pin "manually" by waiting in a loop until the pin changes. - -.. _contents: Contents - :local: - -Overview --------- - -External interrupts are often used to detect when events happen -outside of the Maple. Example events include when a sensor has data -ready to be read, or when a button has been pushed. When such an -event happens, an interrupt is raised, and the Maple stops whatever it -was doing (it is "interrupted"), and reacts to the event by calling a -function (called an *interrupt handler*) which you specify using -:ref:`lang-attachinterrupt`. - -.. _external-interrupts-exti-line: - -Any pin can be used for external interrupts, but there are some -restrictions. At most 16 different external interrupts can be used at -one time. Further, you can't just pick any 16 pins to use. This is -because every pin on the Maple connects to what is called an *EXTI -line*, and only one pin per EXTI line can be used for external -interrupts at a time [#fextisports]_. - -The EXTI Line Pin Map for your board lists which pins connect to which -EXTI lines: - -* :ref:`Maple <maple-exti-map>` -* :ref:`Maple RET6 Edition <maple-ret6-exti-map>` -* :ref:`Maple Mini <maple-mini-exti-map>` -* :ref:`Maple Native Beta <maple-native-b-exti-map>` - -Function Reference ------------------- - -- :ref:`attachInterrupt() <lang-attachinterrupt>` -- :ref:`detachInterrupt() <lang-detachinterrupt>` -- :ref:`libmaple-exti` - -Recommended Reading -------------------- - -* ST manual `RM0008 - <http://www.st.com/web/en/resource/technical/document/reference_manual/CD00171190.pdf>`_ - (PDF), Chapter 9, "General-purpose and alternate-function I/Os", and - Chapter 10, "Interrupts and Events". - -.. rubric:: Footnotes - -.. [#fextisports] The underlying reason for this restriction is that - the external interrupt lines on the STM32 are shared between - :ref:`GPIO ports <gpio-ports>`. There can be only one external - interrupt on each GPIO bit, out of all of the ports. That is, if - PA4 has an external interrupt on it, then PB4 can't have one, too. - Since the GPIO bit numbers only go from 0 to 15, there can only be - 16 external interrupts at a time. |