On Fri, Apr 03, 2009 at 06:23:22PM -0500, Jim Brain wrote:
> Along those lines, is there a document that describes the tape interface  
> from an electrical perspective.  My AVR ASM is quite rusty, so the  
> C2N232 code is not making much sense to me.

The read, write and sense can be mapped to GPIO.  The C2N232 makes use of
the input capture and output compare timer features, but that is not
strictly necessary.  It would be good to map CASS WRITE to a pin that can
generate an interrupt.

The motor voltage is not TTL but something between 6 and 9 volts.  In the
C2N232, this voltage is halved by a resistor divider (4k7+4k7 if memory
serves).

If possible, it could be good to use distinct I/O lines for sense, read and
write on the pass-through port.  (Just connect these lines in the AVR
firmware, e.g., by using the Pin Change Interrupt.)  If this is not
possible or feasible, you should be able to connect the pass-through port
in parallel.  I'm not sure of CASS READ, though.  You'd better check the
schematic diagram of a tape drive.

	Marko

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