Hacking the Toslink Optical?

[coofercat]

I'm tinkering with the optical output on squeezeboxes (I've got a Duet, and a Squeezebox 2). I've got a toslink cable and an optical receiver, which outputs TTL based on how much light is coming down the cable.

I've found that if the SB is on or off, the optical outputs a 1413Khz signal (I don't have an oscilloscope handy, but I assume this is a carrier wave). If I play some audio, then the frequency changes, presumably due to the data coming down the cable ;-)

My original purpose for all this was that I wanted to see if I could use the optical to detect if the SB was switched on or off (so I could subsequently control a relay to turn the amp on or off). I'm not sure there's anything detectable in the optical output between on and off, so I don't think this is going to be possible (so I'll look at other methods of doing the on/off detection).

I am left wondering why the optical stays on when the unit is "off". Further, I'm wondering if it's possible to manipulate the optical output in software in any way? I don't really want to mess with the ability to play audio through the optical (just in case I ever get an optical amp), but at this point, I'm just wondering what's possible.

Anyone got any ideas/info/thoughts/rumours/supposition/anything?

[Phil Leigh]

It's because there is no true "off" unless you disconnect the power. SBs are "always on, always connected" devices...

[TerrynPichardo]

Thank you Phil Leigh now that you explained everything is pretty clear!


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[coofercat]

This is a shame because I'd like to be able to control the amp via the toslink.

I have since got an actual optical amp, which does indeed turn off the output stages then the optical turns off. It does this for our LG television, but obviously not with the SB. Shame, but not the end of the world.

[slimpy]

"Turn off audio"* in player settings - audio is what you are looking for. Setting this to "disable outputs when off" should do the trick.

*When Squeezebox is turned off the digital-to-analog converter and digital outputs can be disabled. Disabling the outputs may cause an audible pop or noise in some receivers.

-s.

[Phil Leigh]

"Turn off audio"* in player settings - audio is what you are looking for. Setting this to "disable outputs when off" should do the trick.

*When Squeezebox is turned off the digital-to-analog converter and digital outputs can be disabled. Disabling the outputs may cause an audible pop or noise in some receivers.

-s.

This doesn't turn off the TOSLINK transmitter though. The LED's are always operational. It just means no signal is being encoded onto the TOSLINK connection. The amp may still see the (empty) signal and stay turned on...

[coofercat]

I'll try that "disable outputs" option - I hadn't noticed that in settings. I'll get an oscilloscope on the RX'd data line and see if I can see any difference when it's enabled or not. Even if a real amp won't switch on/off, perhaps a bit of custom electronics can do it instead ;-)

[Pascal Hibon]

There is a PowerSwitch II plugin with sends out a signal to the headphone jack of the Squeezebox. With that signal you can drive a SSR or a Relay (through a transistor) to switch your amp on and off. Maybe that is a solution for what you’re trying to accomplish?
http://www.gwendesign.com/slimserver...#powerswitchii

[coofercat]

I saw that a while back, but had completely forgotten about it.

I also realised that I made a mistake on my original post - I've got a couple of Receivers, and a Squeezebox 1 (not 2). It looks like the idea above won't work on the SB1, but I'm wondering if it may be time to upgrade ;-)

Either way, the "turn outputs off" option doesn't turn off the laser in the Toslink, but I've yet to get the oscilloscope on there and see if something else happens to it that I could detect.

Thanks again for all the ideas - it's all been very useful.

[Aanbeeld]

Hm, reading this post i'm wondering. When my squeezebox 1 is off the amp doesn't see a digital input anymore nd changes to analog input. So there must change something on the digital output.