Update readme.

README.md

@@ -8,18 +8,25 @@ A firmware for the
 
 * 6KRO (6 simultaneous keys, not including modifiers)
 * Software debouncing
-* Multiple layers (limited only by memory)
-* Bind arbitrary Scheme functions to a key
+* Multiple layers, momentary and sticky (limited only by memory)
 * Combo keys (a single keystroke can send a modifier and a non-modifier)
+* Bind arbitrary Scheme functions to a key
+* ~255 lines of code
 
 ## Usage
 
+This currently requires Microscheme with the addition of
+`vector-copy!` which at the time of this writing is only available on
+[this branch](https://github.com/ryansuchocki/microscheme/pull/31).
+
 Replace `/dev/ttyACM0` with the path your OS assigns to the USB
 bootloader of the microcontroller:
 
     $ make upload USB=/dev/ttyACM0
 
-Currently only the "multidvorak" layout is supported.
+On Mac OS X sometimes the USB path is `/dev/cu.usbmodem1411` or similar.
+
+Currently only the "multidvorak" layout is included.
 
 ## Development
 
@@ -29,8 +36,17 @@ into Racket and simulates the GPIO functions with a test harness:
 
     $ make test
 
+## Known bugs
+
+If you hold the fn key, press a button (say Q) and then release fn
+without releasing Q, it will send a keycode for Q rather than simply
+leaving the previous fn+Q keycodes as held down.
+
 ## License
 
 Copyright © 2014-2019 Phil Hagelberg and contributors
 
 Released under the [GNU GPL version 3](https://www.gnu.org/licenses/gpl.html).
+
+Uses [PJRC USB Keyboard library](http://www.pjrc.com/teensy/usb_keyboard.html)
+which is Copyright © 2009 PJRC.COM, LLC and released under the MIT/X11 license.