Add note about AND gate to README

diff --git a/README.rst b/README.rst
index bd54bd1869c8afde30b4fde1728009aa4a0caf51..91f5490f0289306e269e706e6fded1fda292f769 100644 (file)
--- a/README.rst
+++ b/README.rst
@@ -3,9 +3,12 @@ Remote Touch Lamp
 #################
 
 This somewhat sizable project is a re-implementation of
-``http://filimin.com/`` of sorts.  It speaks MQTT and uses a CAP1188 for
+http://filimin.com/ of sorts.  It speaks MQTT and uses a CAP1188 for
 local touch sensing.  Display is via a grid of so-called "NeoPixel" LEDs.
 
+Motivation, pictures, and additional discussion can be found at
+http://www.ietfng.org/nwf/ee/purple-lamp.html
+
 Hardware V1
 ###########
 
@@ -51,6 +54,22 @@ stack the RGB array atop the ESP8266 and hookup via the Doubler's female
 headers, or do away with the Doubler entirely and hook the male pins on the
 ESP8266, etc.
 
+Revision 1.1
+============
+
+An AND gate (actually, a 7408) was added to gate serial access to the
+WS2812.  On boot, the ESP8266 emits debugging information to its alternate
+serial console, which is also the ws2812 data source.  This results in some
+blindingly bright light when the machine boots or crashes.  The AND gate
+effectively prevents the chip from writing to the ws2812 matrix unless
+another GPIO is pulled high as well.
+
+The WS2812 LED array from AdaFruit allows for one of many pins to be
+selected for the WS2812 input line; as the ESP8266 does not use all of the
+possible I/O lines of the Feather design, a free signal (N/C to the ESP8266
+Feather Huzzah CPU board) was chosen instead and the AND gate's output
+routed back into the stack on this line.
+
 ESP IO
 ######
 
@@ -59,6 +78,8 @@ The various boards are interfaced as follows:
 +--------------+----------------------------------------------------------+
 | ESP GPIO Pin | Function                                                 |
 +--------------+----------------------------------------------------------+
+| 0            | WS2812 AND-gate input (see above)                        |
++--------------+----------------------------------------------------------+
 | 2            | WS2812 serial shift out (to LED array input)             |
 +--------------+----------------------------------------------------------+
 | 4            | I2C SDA pin (to CAP1188, optional expansion)             |