diff --git a/firmware/Makefile b/firmware/Makefile
new file mode 100644
index 0000000..9cc38ce
--- /dev/null
+++ b/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
diff --git a/firmware/gen-dac-lookup.pl b/firmware/gen-dac-lookup.pl
new file mode 100755
index 0000000..0a4cc17
--- /dev/null
+++ b/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";
+}
diff --git a/firmware/lookup.inc b/firmware/lookup.inc
new file mode 100644
index 0000000..49f7130
--- /dev/null
+++ b/firmware/lookup.inc
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