1 files changed, 32 insertions, 87 deletions
diff --git a/source/external-interrupts.rst b/source/external-interrupts.rst
index b2cbbb1..ac065a4 100644
--- a/source/external-interrupts.rst
+++ b/source/external-interrupts.rst
@@ -6,73 +6,42 @@ External Interrupts
 ===================
 
 External interrupts can be used to trigger routines to run in response
-to changes in voltage on a pin. Each GPIO pin on the Maple can be used
-to detect transitions such as when the voltage goes from low to high,
-or from high to low. This technique can be used to avoid unnecessary
-polling of the state of a pin.
+to changes in voltage on a pin.  Each :ref:`GPIO pin <gpio>` can be
+used to detect transitions, such as when the voltage goes from
+:ref:`LOW <lang-constants-low>` to :ref:`HIGH <lang-constants-high>`,
+or from ``HIGH`` to ``LOW``. 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 microcontroller. These can be used to tell the Maple
-when events happen, such as 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 can react to it with a preset
-*interrupt handler*.
-
-Every GPIO pin on the Maple can be used as an external interrupt,
-subject to certain constraints; there can be a maximum of 16 different
-external interrupts set up at a time on the Maple. This is because the
-external interrupt lines on the STM32 are multiplexed between GPIO
-ports. In effect, this means that every pin on the Maple maps to a
-certain EXTI line, and within that EXTI line, only one of the pins
-that maps to it can be used as an external interrupt at a time.
-
-The following table shows which pins can be used on which lines.
-
-.. list-table::
-   :widths: 1 1
-   :header-rows: 1
-
-   * - EXTI Line
-     - Maple pins
-   * - EXTI0
-     - 2, 15, 27
-   * - EXTI1
-     - 3, 16, 28
-   * - EXTI2
-     - 1, 17, 25
-   * - EXTI3
-     - 0, 18
-   * - EXTI4
-     - 10, 19
-   * - EXTI5
-     - 4, 13, 20
-   * - EXTI6
-     - 5, 12, 35
-   * - EXTI7
-     - 9, 11, 36
-   * - EXTI8
-     - 6, 14, 37
-   * - EXTI9
-     - 7, 25, 28
-   * - EXTI10
-     - 8, 26, 29
-   * - EXTI11
-     - 30
-   * - EXTI12
-     - 31
-   * - EXTI13
-     - 21, 32
-   * - EXTI14
-     - 22, 33
-   * - EXTI15
-     - 23, 34
+outside of the microcontroller. These can be used to tell Maple when
+events happen, such as 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 can react to it with a preset
+*interrupt handler*, which is a function that gets called whenever the
+event occurs.
+
+.. _external-interrupts-exti-line:
+
+Every GPIO pin can generate an external interrupt, subject to certain
+constraints.  There can be a maximum of 16 different external
+interrupts set up at a time.  This is because the external interrupt
+lines on the STM32 are shared between GPIO ports. In effect, this
+means that every pin on the Maple connects to what is called an *EXTI
+line*, and within an EXTI line, only one of the pins that connects to
+it can be used to detect external interrupts at a time.
+
+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>`
 
 .. note::
 
@@ -80,40 +49,16 @@ The following table shows which pins can be used on which lines.
    desired pin to an input mode (e.g ``INPUT`` or ``INPUT_FLOATING``,
    ``INPUT_PULLUP``, ``INPUT_PULLDOWN``).
 
-
 Function Reference
 ------------------
 
 - :ref:`attachInterrupt() <lang-attachinterrupt>`
 - :ref:`detachInterrupt() <lang-detachinterrupt>`
 
-Code example
-------------
-
-Blink the LED on every transition::
-
-    int pin = 13;
-    volatile int state = LOW;
-
-    void setup() {
-      pinMode(pin, OUTPUT);
-      pinMode(0, INPUT_FLOATING);
-      attachInterrupt(0, blink, CHANGE);
-    }
-
-    void loop() {
-      digitalWrite(pin, state);
-    }
-
-    void blink() {
-      state = !state;
-    }
-
-
 Recommended Reading
 -------------------
 
-* STMicro documentation for STM32F103RB microcontroller:
-
-      * `Datasheet <http://www.st.com/stonline/products/literature/ds/13587.pdf>`_ (pdf)
-      * `Reference Manual <http://www.st.com/stonline/products/literature/rm/13902.pdf>`_ (pdf)
+* ST manual `RM0008
+  <http://www.st.com/stonline/products/literature/rm/13902.pdf>`_
+  (PDF), Chapter 9, "General-purpose and alternate-function I/Os", and
+  Chapter 10, "Interrupts and Events".