ETHPIC Node 5 is the audio control node, which provides control of power and input selection for my audio system (I was going to write Hi Fi here but any audiophile would cringe at the quality of reproduction, so we'll just say audio!). Under the control of the Polly server, this node switches mains power to the rest of the audio gear. It provides a choice of one of four audio sources and also allows all four to be off, for when I am listening to one of the less often used sources. A watchdog system is also provided, whereby the system is shut down after a period of silence. Being part of the Polly system provides other functions, such as switching off the system when I leave the house. Following an occasion when I didn't hear someone at the door due to having the music on loud, Polly also turns off the audio system when someone rings the doorbell!
As with all the nodes in the Polly system, the logic controlling all the above functions is performed in the server. The actual functions of this node are:
- Switch audio signals and mains power as instructed by the server.
- Report sound or silence to the server.
- Report switch presses to the server.
- Illuminate the switches (steady or flashing) as instructed by the server.
Here's a collection of pictures of what is the most complicated ETHPIC node so far completed under construction:
This is a small interface board sold by Modtronix, which plugs onto the SBC65 allowing me to add my own circuitry.
Audio control board under construction. Buffer amplifiers top and far right, and four reed relays bottom left.