Easy path: two tone detectors, going to a
microcontroller who store the
data read from the tape and send it in RS232 way. A very simple AVR
microcontroller can do that ;o)
Argh!. I grew up learning to design solutions to problems, rather than
throw microcontrollers at them in the hope they'd go away.
For the standard 1200/2400Hz cassette tones, there's a very simple
circuit using a pair of monostables (one-shots) -- IIRC a single 74LS123
chip will do -- that does the decodning from the tones to a bitstream.
BTW, if you've got tone detectors (presumably one tuned to the '1' tone,
the other to the '0' tone), why do you need a miocrocontroller to turn
the output into a bitstrea?. A few logic gates is a lot simpler.
-tony