Sensor Watch Simulator (#35)

* Put something on screen

* Use the 32bit watch_date_time repr to pass from JS

* Implement periodic callbacks

* Clear display on enabling

* Hook up watch_set_led_color() to SVG (green-only)

* Make debug output full-width

* Remove default Emscripten canvas

* Implement sleep and button clicks

* Fix time zone conversion bug in beats-time app

* Clean up warnings

* Fix pin levels

* Set time zone to browser value (if available)

* Add basic backup data saving

* Silence format specifier warnings in both targets

* Remove unnecessary, copied files

* Use RTC pointer to clear callbacks (if available)

* Use preprocessor define to avoid hardcoding MOVEMENT_NUM_FACES

* Change each face to const preprocessor definition

* Remove Intl.DateTimeFormat usage

* Update shell.html title, header

* Add touch start/end event handlers on SVG buttons

* Update shell.html

* Update folder structure (shared, simulator, hardware under watch-library)

* Tease out shared components from watch_slcd

* Clean up simulator watch_slcd.c inline JS calls

* Fix missing newlines at end of file

* Add simulator warnings (except format, unused-paremter)

* Implement remaining watch_rtc functions

* Fix button bug on mouse down then drag out

* Implement remaining watch_slcd functions

* Link keyboard events to buttons (for keys A, L, M)

* Rewrite event handling (mouse, touch, keyboard) in C

* Set explicit text UTF-8 charset in shell.html

* Address PR comments

* Remove unused directories from include paths

watch-library/hardware/hal/documentation/ext_irq.rst

@@ -0,0 +1,39 @@
+==============
+EXT IRQ driver
+==============
+
+The External Interrupt driver allows external pins to be
+configured as interrupt lines. Each interrupt line can be
+individually masked and can generate an interrupt on rising,
+falling or both edges, or on high or low levels. Some of
+external pin can also be configured to wake up the device
+from sleep modes where all clocks have been disabled.
+External pins can also generate an event.
+
+Features
+--------
+* Initialization and de-initialization
+* Enabling and disabling
+* Detect external pins interrupt
+
+Applications
+------------
+* Generate an interrupt on rising, falling or both edges,
+  or on high or low levels.
+
+Dependencies
+------------
+* GPIO hardware
+
+Concurrency
+-----------
+N/A
+
+Limitations
+-----------
+N/A
+
+Knows issues and workarounds
+----------------------------
+N/A
+