Disc analyser status update -- it works!

Philip Pemberton classiccmp at philpem.me.uk
Sat Nov 21 18:53:13 CST 2009

Quick status update before I go to bed...

The analyser is now reading discs. All the buffer data seems valid, and 
the nifty "so simple I can't believe I didn't think of it first" 
counter-rollover algorithm proposed by Peter Coghlan seems to work 
really nicely too.

I've dumped track zero from a DOS 1.4MB floppy and (after a quick bit of 
histogram analysis) it looks like valid MFM data. I'm seeing a big spike 
at ~2us, a second, smaller, spike at ~3us, and a third, even smaller 
spike at ~4us. The last spike is only just noticeable on a linear graph 
scale -- probably due to the large number of 2us "hits" (39,000 in a 
90,000 sample acquisition). On a log scale it's a lot more visible.

I haven't tried decoding the data yet, but that's next on the list.

Writing isn't implemented yet (I need to do a partial-rewrite and 
redesign of the disc writer state machine) but I'm quite happy with how 
this has turned out thus far.

I'd post screenshots, but console apps don't tend to make very 
interesting screenshots...

(I'd also cross-post this to VCforum, but I'm too tired to remember my 

classiccmp at philpem.me.uk

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