18 Nov
2009
18 Nov
'09
8:27 p.m.
On Wed, 18 Nov 2009, Cameron Kaiser wrote:
The Tutor doesn't save tape as FSK or KCS;
it's actually just pulses, i.e.,
-||-|--|-||-|--|--
It reminds me more of the Commodore Datasette than the Texas Instruments
machines the Tutor was descended from, actually.
The trick with decoding it wasn't per se figuring out the frequencies, it
was figuring out what pulse pattern meant which bit, and then shuffling the
bits around until I got some sort of framing that made sense. But that's
what makes the playback problem mystifying because this should be very
simple to generate and play back. I don't see what a filter would do to help
here necessarily unless I'm misunderstanding the alleged purpose.
Look at the waveform. In addition to the outgoing waveform that you are
recording accurately, look at the incoming waveform produced by the POS
recorder. Could the Tomy be expecting (and relying) on certain
degradations of the signal? Howzbout a pulse extender circuit or
software?