Marko Mäkelä wrote:
> 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
>
>        Message was sent through the cbm-hackers mailing list
> From - Sun
>   
My apologies for the delay, but I'm jsut now getting to this.  Here's my 
thoughts:

http://www.jbrain.com/vicug/gallery/c2npower

A simple 'carrier' board that I can immediately use as a power tap, but 
has through-hole parts, so it can be stuffed by anyone and used for 
various projects.

Now that I've put the schematic up, I realize I probably need to feed 
MOTOR into the uC (via a voltage divider) so the uC would know when the 
system is asking for data.

Any thoughts?

I am trying to balance my immediate need (power tap) with the fact that 
PCBs cost pretty much the same, regardless of whether there are holes 
drilled or not.  I did not put Xtal or caps on the design, assuming that 
one could trim the built-in oscillator for satisfactory operation, but I 
could be persuaded to add them if folks think it would provide a lot of 
benefit?

Jim

-- 
Jim Brain, Brain Innovations                                      (X)
brain@jbrain.com 
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times! 
Home: http://www.jbrain.com


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