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gtnicol



Joined: 27 Dec 2005
Posts: 334
Location: Rhode Island, USA
PostPosted: Thu Jan 20, 2011 8:52 pm    Post subject: Keyboards and mice Reply with quote
In the process of building the adapter/soundboard replacement I threw a logic analyzer on pins 3, 4, and 5 of the DB-19 connector, and got the following while playing a sound. That's encouraging because it seems like at least I can figure out what the bus speed etc. is and have some chance of figuring out the protocol for sending sounds to the soundbox. OTOH, for the life of me, I can't capture the keyboard and mouse data. I would have expected to see the data on these pins, because according to the documentation, everything else is a ground, power, or power button (and the way the wires in the cables are laid out implies that for each top-row pin, there is a paired ground).

FWIW. I'm looking for the bit pattern degs has written up in his analysis, but from talking to him, it seems he might have been sampling elsewhere... possibly directly from the chips.

[img]http://www.flickr.com/photos/15578792@N02/5374596670/in/set-72157625871471438/[/img]
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cubist



Joined: 20 Sep 2007
Posts: 209
Location: Cambridge, MA
PostPosted: Sun Jan 30, 2011 10:43 pm    Post subject: Re: Keyboards and mice Reply with quote
gtnicol wrote:
[img]http://www.flickr.com/photos/15578792@N02/5374596670/in/set-72157625871471438/[/img]


I can't see a damned thing in that image (when I make it work) and I have no idea what the pin-to-channel assignment was or your test setup. But pins 3, 4 and 5 should be it. Needs to be at least a 1.3 Mb/S path for audio. No idea if it clocks continuously. There's also very little isolation between those pins and the system chip. Be careful.
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gtnicol



Joined: 27 Dec 2005
Posts: 334
Location: Rhode Island, USA
PostPosted: Sun Jan 30, 2011 11:27 pm    Post subject: Reply with quote
The pin to channel assignments are:

Pin 3 - clock
Pin 4 - data out
Pin 5 - data in

Basically, I spliced a header into the DB-19 connector and connected probes to the pins there.

I haven't got much further on this... mostly due to lack of time. Basically, if I play a sound, I can see the data being sent to the soundbox (data out), with some data being sent back to the computer (data in, I'm assuming there's some protocol there), which is what you see in that image. The clock rate appears to be 5MHz.

As I noted, I still haven't been able to see the keyboard. I'm basically trying to reproduce degs results and haven't been able to do so. It might be a problem with the logic analyzer I have... the MSO-19 is a USB based logic analyzer and it's sample depth isn't that great.
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gtnicol



Joined: 27 Dec 2005
Posts: 334
Location: Rhode Island, USA
PostPosted: Mon Jan 02, 2012 6:05 pm    Post subject: Reply with quote
A bit of an update on my blog (hah!). I spent some time over New Year getting things set up, and it looks like degs was missing the clock information.

http://www.mind-to-mind.com/blog/blog.html

Once I get a PIC reading/writing NeXT data, I'll put together a complete specification.
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