Add BOOTSEL documentation (earlephilhower#1722)

earlephilhower · efp3-kioxia · web-flow · commit 39238a505d27 · 2023-09-21T08:34:39.000-07:00
Co-authored-by: Earle F. Philhower, III &lt;earle.philhower@kioxia.com&gt;
diff --git a/docs/bootsel.rst b/docs/bootsel.rst
@@ -0,0 +1,21 @@
+BOOTSEL Button
+==============
+
+The BOOTSEL button on the Pico is not connected to a standard GPIO, so
+it cannot be read using the usual ``digitalRead`` function.  It **can**,
+however, be read using a special (relatively slow) method.
+
+The ``BOOTSEL`` object implements a simple way of reading the BOOTSEL
+button.  Simply use the object ``BOOTSEL`` as a boolean (as a conditional
+in an ``if`` or ``while``, or assigning to a ``bool``):
+
+.. code:: cpp
+
+    // Print "BEEP" if the BOOTSEL button is pressed
+    if (BOOTSEL) {
+        Serial.println("BEEP!");
+        // Wait until BOOTSEL is released
+        while (BOOTSEL) {
+            delay(1);
+        }
+    }
diff --git a/docs/index.rst b/docs/index.rst
@@ -30,6 +30,7 @@ For the latest version, always check https://github.com/earlephilhower/arduino-p
 
    Analog I/O <analog>
    Digital I/O <digital>
+   BOOTSEL Button <bootsel>
    EEPROM <eeprom>
    I2S Audio <i2s>
    PWM Audio <pwm>
