killswtch's Home Automation and Media Projects
This is the story of my attempts at integrating various technologies into a 3-bed semi, constructing as much of the hardware and electronics as possible myself.
Sunday 17 February 2008, 5:49 PM
The VAMS-0808 matrix switcher and determining its protocol
A significant part of the whole-house audio system is the matrix switch that allows any audio input to be listened to on any audio output. I’ve been looking for a suitable switch for several months now (by suitable I mean cheap enough, but still capable). My requirements are that it has 8 inputs, 4 outputs and RS232 support.
Once again, eBay has proven it’s worth and I’ve found something for a lot cheaper than my previous find. It has 8 inputs, 8 outputs, RS232 support and includes composite video switching too. S-video switching would have been nice, but that feature seems to double the price so I’m happy to go with the compromise of composite video.
Of course there’s always a hitch with these low-cost items made in the far-east, and it’s almost always that the websites are absolutely rubbish - crafted to work only in IE, badly structured, lacking any useful technical information and generally broken. Thankfully, Google has come to the rescue and I’ve managed to find the software that controls the VAMS-0808 (IE is required, and the installer doesn’t even open in Vista - works OK in XP though).
I’ve got a Virtual PC with XP installed, just to connect to work’s VPN which until recently didn’t have a Vista client. One of the handy features in Virtual PC is the ability to map COM ports to physical ports, named pipes or a text file. I set COM2 to redirect to a text file, and voila, I now know how the software talks to the switcher.
Communication protocol for the VAMS-0808 (not tested yet)
This is what I’ve figured out so far:
All commands start with a 0 (zero), and are committed with a Windows new-line (\r\n). Some actions require multiple commands in order, for example channel switching. An output channel selection command must precede an input channel selection command.
0CO1 - 0CO8: Select output channel 1-8
0ALL: Select all output channels
0CI1 - 0CI8: Set input channel 1-8 for currently selected output channel
0OFF: Disconnect all output channels (input channel 0)
0VCS: Subsequent commands switch only video
0ACS: Subsequent commands switch only audio
0AVS: Subsequent commands switch both audio and video
0LOO: Disable hardware lock
0LOI: Enable hardware lock
I have no idea if the switch actually returns any status codes since I haven’t got it yet, but hopefully it’ll be on it’s way to me soon!
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