add lookup table for DAC mapping

git-svn-id: https://bucket.mit.edu/svn/nilm/zoom@8026 ddd99763-3ecb-0310-9145-efcb8ce7c51f

firmware/Makefile

@@ -0,0 +1,7 @@
+all: lookup.inc
+
+lookup.inc: gen-dac-lookup.pl
+	perl gen-dac-lookup.pl > lookup.inc
+
+show: lookup.inc
+	echo 'plot "lookup.inc" with lines' | gnuplot -persist

firmware/gen-dac-lookup.pl

@@ -0,0 +1,13 @@
+#!/usr/bin/perl
+
+srand(1337);
+
+# constant bits, the rest are filled with random data
+$bits = $ARGV[0] || 10;
+
+$rem = 16 - $bits;
+for ($i = 0; $i < 2**$bits; $i++)
+{
+    $out = $i * 2**$rem + int(rand(2**$rem));
+    print $out . ",\n";
+}