really remove NOTES (didn't do that in previous commit)

NOTES

@@ -1,97 +0,0 @@
-design specs:
-- text readable at up to 50 m
-- automatic centering of image
-- non-aggressive design
-- suitable for dim ambient light, such as an illuminated street
-  at night
-- powered by off-the shelf batteries
-- content programmable via wireless interface
-- use medium-strength authentication for wireless communication
-
-opportunistic component selection:
-- reuse ben-wpan (IEEE 802.15.4) circuit, and ben+atben or
-  laptop+atusb for (remote) editing
-- use ATmega 48/88/168 series controller
-- use ADXL321 series acceleration sensor
-- use APTD1608SEC LEDs
-- use unregulated battery power
-
-visible field:
-- height: ~25 cm, with 16 pairs of LEDs, at 8 mm spacing
-- horizontal movement (arm waving) is about 120 cm
-- this yields up to 80 horizontal square "pixels"
-- text capacity
-  height width gap  character (per line)
-  16 px  10 px 2 px  6.8
-   7 px   5 px 2 px 11.7
-   7 px   5 px 1 px 13.5
-- text height
-  pixels cm
-   16    24
-    7    11.2
-
-physical structure:
-- mount LEDs on stick
-- batteries and main circuit in handle or extension (see below)
-- make stick strong enough to resist excessive bending/breaking
-  under wind load
-- make stick as weak as possible to avoid perception or use as
-  weapon
-
-stick length:
-- LEDs occupy (16*2-1)*8 mm plus component width, in total
-  roughly 249 mm
-- add 2 cm for termination at top
-- add extension for increased visibility
-
-extension:
-- assume small spectators are 10 cm smaller than nearby
-  obstacles (e.g., shoulders of tall people)
-- assume distance between spectators is 80 cm
-- to be visible at 50 m, the bottom edge must therefore be
-  50 m / 80 cm * (10 cm / 80 cm) * 10 cm = 78 cm
-  above eye level of small spectators
-- assume waver to be about 20 cm taller than small spectator
-- hand above head position yields distance of about 30 cm
-  above eye level
-- therefore, extension should be 78 cm - 50 cm = 28 cm
-
-handle design:
-- about 10-12 cm in length
-- include button for control functions. button can be located
-  on extension
-- acceleration sensor should be at a high position, possibly
-  on extension
-
-overall length:
-- 25 cm for LEDs
--  2 cm for termination (head)
-- 28 cm for extension
-- 12 cm for handle
-- 67 cm total length
-
-electrical, LEDs:
-- no multiplexing
-- max. 30 mA per LED pair (series)
-  -> max. 16 * 30 mA = 480 mA for LEDs
-- series resistor is 56 Ohm. Allow up to additional 10% voltage drop
-  in trace.
-  -> Rmax per LED pair is ~ 5 Ohm
-- assume 30 cm trace
-- variant A: switching transistors at LED
-  - average length is 15 cm
-  - Rmax is 5 Ohm / 16 = 300 mOhm
-  - http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/
-    yields for 500 mA at 2 oz/ft2:
-    - minimum width 2.3 mil / 0.06 mm
-    - 111 mOhm
-  => 8 mil traces are more than sufficient, even for power rails
-- variant B: switching transistors in handle
-  even less demanding
-
-authentication:
-- shared secret (128 bit, SHA1-hashed text with 128 bit salt)
-- salt (128 bit)
-- SHA1 from avrcryptolib
-- due to chip limitations, the secret key for firmware updates is sent
-  in the clear