Add some notes

HPGLWrap.py

@@ -4,6 +4,12 @@ import os
 import re
 import sys
 
+# Based off of notes from
+# https://github.com/fellesverkstedet/gcc-laserpro-driver
+# and http://www.wiki.cl.cam.ac.uk/rowiki/CompArch/HardwareLab/LaserCutter
+# and src/core/path_gcc.c from
+# https://github.com/fellesverkstedet/fabmodules
+
 def write_pen_values(values, char):
     return "!v64" + char + "".join(["{:04d}".format(value) for value in values])
 
@@ -32,7 +38,7 @@ def pre_content(filename, power, speed, rate, pen_settings):
 
     # Select first (and only) pen (commented out in original source)
     # outString += "!v1D"
-    # outString += "!m2A" # might cause autofocus?
+    # outString += "!m2A" # triggers autofocus
 
     # Use same value for all 16 pens
     # doesn't seem to affect vector settings
@@ -52,6 +58,7 @@ def set_vector_pens(content, pen_settings):
             power=pen_settings['power'][num],
             speed=pen_settings['speed'][num],
             penNum=num+1) for num in range(0, 16)])
+    # TODO: find out why slow movement in PU (pen up) until first PD (pen down)
     content = re.sub(
         "FS\d{1,4};VS\d{1,4};SP1;",
         settings + "SP1;",