Re: Real Time Clock on Cassette Write/Sense lines

On 02/11/2012 06:02 PM, Jim Brain wrote:
>
> Full disclosure: Many products require a source of 5VDC from the
> machine, and the cassette port is an ideal location. Such pigtails
> requires a small PCB to create the passthrough portion. When I initially
> designed the cassette passthrough PCB, it bothered me that it was mainly
> a waste of PCB space. So, extended it just a tiny bit, mainly to make it
> easier to grab onto for removal, and added a DIP14 footprint matching a
> ATTINY24/44/84 uC, a simple voltage divider for the motor line, and some
> jumpers for READ/WRITE/SENSE. I didn't have any expectations for use,
> but it seemed better than leaving the PCB plain. Now, I need to make a
> new order, and thought I might add an RTC, because it's a simpler idea
> (no uC programming needed, just install an RTC and write some 6502
> code). It's a through-hole design, and parts can be sourced easily, so I
> thought it would make a neat DIY project. Anyway, that's why it's external.

If you want to use the motor line for I2C, but still be able to use the 
tape drive, why not set up a low pass filter on it so the motor line 
that the tape drive sees only gets activated if there is a true static 
signal on the line and not the I2C data or clock.

  Gerrit


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