added hexinverter higher gate fix to errata of 0.9

readme.md

@@ -16,3 +16,8 @@ The device runs on a single 9V battery and outputs it's signal on a 6.3mm audio
 There is a mistake with the output power switching in revision `0.9` – gladly this is easily fixed, by drilling away a pad and bridging a connection: 
 
 ![](images/0.9_fix_jack.png)
+
+The footprint of the hexinverter chip had the in- and outputs of the right side swapped. Fix: using some resistor legs like this:
+
+![](images/0.9_fix_40106.png)
+