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.
Tuesday 18 March 2008, 8:29 PM
The VAMS-0808 matrix switcher and determining its protocol - part 2
As I mentioned last month, I bid on and won an 8×8 AV matrix switcher on eBay. The switcher arrived the Monday following the Saturday that I won it (speediest delivery ever!), so I took it home and plugged it all in.
I rummaged around for a serial cable to connect the switcher to boron, the Ubuntu file server and found something that I thought would do the job. Sadly the switcher has a male connector, whereas for a standard serial cable it should be a male connection on each end. So, slightly disappointed, I went ahead and ordered a M-F serial extension from eBay, assuming that this would do the job. This attempt also failed - the matrix switcher would not respond to any of the commands that I thought it should, and nothing was being returned either. After a bit more research in the little documentation that I had I noticed that the switcher requires a cross-over cable AKA a null modem cable.
The next cable I ordered was a M-M cable, so I got an M-F converter at the same time. Success! I now have the ability to control the matrix switcher via the RS232 on boron.
The following weekend I set about writing a prototype of the software to communicate with the switcher. The switcher operates in such a way that state is important, since switching channels requires at least 2 commands and at any time someone can press a button on the front panel to issue any command.
When a button is pressed on the front, a message is sent via the serial port to indicate the action that has taken place. Similarly, when an instruction is sent to the unit over the serial connection a reply is received indicating whether that command succeeded or not. Sometimes the switcher doesn’t notice that it’s been sent an instruction, so to get around that I ended up sending the same message up to 3 times.
The resulting prototype works quite well. I may release the source code at some point.
There’s a video demonstrating the software and the switcher.
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!
Sunday 17 February 2008, 5:45 PM
Re-running cables
There are two main wiring routes that are part of my ongoing project to wire up our house for A/V and data distribution - one goes from the bottom of my wardrobe directly down to the room below, and the other goes across a short stretch of the landing and down into the pantry.
Until yesterday, the 4 x speaker and 6 x CAT5 cables going to the pantry were laid under the carpet, then pushed down through a hole in a floodboard and the corresponding hole in the pantry ceiling. The reason for this was simply that it was too much work at the time to run the cables properly, i.e. beneath the floorboards. At the time when I was running the cables, we weren’t living in the house so I only had relatively short visits in which to do the work.
I spent most of yesterday improving the situation by pulling up flooadboards, drilling holes in joists and reaching around in the dirt. All but 2 of the cables that were fed under the carpet are now out of sight under the floorboards of the landing. The remaining 2 cables are CAT5 feeds to bedroom 3, which take a slightly different route to the main runs and are already connected at both ends.
The floor boards were lifted using a reciprocal saw, which cut through the thick ~100-year-old planks like a knife through butter that’s just come out of the fridge. The holes in the joists were mostly drilled using a 32mm drill bit, the largest I had available.
There was one close call with an unexpected mains cable which had been routed through the joist only a few millimetres from the floorboard I was cutting into. Fortunately the outer insulation was barely grazed.
Before the cables were re-routed, they had to be pulled back up through the pantry ceiling. As the photo below shows, this resulted in a lot of spaghetti! Running each cable individually allowed me to untangle the mess and straighten the cables out.
The speaker cables were run first since they are larger and heavier, and so naturally like to sit at the bottom of the holes. The CAT5 runs were pulled in the order that they come through the bedroom/landing wall, so as to keep them as neat as possible.
Now that the cables have been run, I can continue with the wiring project by adding the endpoints - the RJ45 sockets and speakers. More on the progress of this soon.
Tuesday 15 January 2008, 9:47 PM
Resurrecting a dead amplifier - the continuation
At the end of last year I tested the prototype of the matrix audio switcher, in the process blowing up part of the amplifier that powers the speakers in the living room. After investigating the damage, I found a great site to buy the replacement parts from. They arrived before Christmas, but I didn’t get around to installing them until recently.
The new transistors are exactly the same as the dead ones, so it was just a matter of unsoldering the old ones and replacing them. The nice chunky pads (compared to all the SMD boards I’m used to handling as computer parts) were lovely to work with, and the work was done in a matter of minutes. Minutes + £6 of parts = one big saving over a new amplifier and a lot of waste electronics. If only all devices were this easy to fault-find and fix.
With a fire extinguisher at the ready and my adrenaline gland just waiting to explode, I switched on the repaired circuit and ….. near silence, just the sound of the fan - it worked! Now that both channels are actually wired to something rather than one of them shorting out, the sound coming out is pretty good. In a few months the whole system should be up and running.
Sunday 13 January 2008, 4:56 PM
What's next?
The Homebrew Challenge gave me a reason to progress my projects, but over Christmas things have slowed down. Winning the competition has given me some money from the sale of my old car, so it seems fitting that the money is put towards finishing the current projects. This is my plan for the projects over the next few months.
January 2008
Purchase Zone 2 amplifier, Zone 4 amplifier
Improve rack ventilation
February 2008
Purchase Zone 3 amplifier, DVI/USB KVM
March 2008
Purchase Matrix switcher
April 2008
4u blanking plate, 1u blanking plate
Write control software
The full list of things to do/purchase over the next 2 years is available on my other blog.
I have purchased the 2 amplifiers for this month from eBay, but haven’t got around to the ventilation improvements as yet.
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