For my embedded course at the University of Lucerne of Applied Sciences and Arts I needed more Bluetooth modules for the Zumo/Sumo robots. I run out of stock as the modules are getting popular and are used in many student projects. So I ordered a handful more from DX/DealExtreme of the same HC-06 type/part number I already ordered a while back. I expected that they will work as the modules I had ordered from DX half a year ago. Was that naïve? Probably. Because they did *not* work, and caused me to reverse engineer the modules and to apply a hardware fix to get them working….