[Valkyrie-MT] was frustrated by the inability to control TrueHD audio volume from his computer. That’s because digital audio passes through the cable to the receiver where the volume adjustments are done. This meant that his RF computer remote was no good because the receiver uses an IR remote. He set out to find a way to get around this and ended up working with the Consumer Electronics Control (CEC) protocol.
The CEC protocol is a 1-wire serial bus built into the HDMI standard. The solution he settled up required one solder connection on the motherboard as well as the internal USB translator module seen above. That translator box, called the RainShadow, is a PIC 18F87J50 controlled board that translates incoming commands from the USB connection and sends them out as CEC hex codes. A bit of code writing and [Valkyrie-MT] is in business. You can see in the video after the break that it’s not just controlling audio, he can now control the entire entertainment center including turning on the TV and setting it to the appropriate input.