>> Have anyone designed a one pin interface?

>Ever heard of an ICE?

Can«t afford 100 ICE units spread around the customers...
And they don«t fit into the box.
And dont run on that little battery.
And the costomers then would have to learn a lot more to be able to edit
simple parameters.

What I want is more like a attachable keyboard and display, where the most
user interface processing is done in that unit, so the code in target is
small and don«t use much execution time. And driven by as little pinning
and cheap connector and other hardware (any?) as possible, since it would
be nice to leave this option also in production. Nice for in-field testing,
parameter change, loggs read from EPROM, if the target is a C84.

If it works good I plan to use it as normal display for one project too!

Multitasking
It is possible to let it not interfere with the running processes, since it
can be hooked onto a moderately fast timer interrupt.

Protocol
I have some suggestions, (or a lot rather) in a bunch of handwritten pieces
of paper. Roughly, the target is the master, so it decides the speed, and
don«t have to keep listening or synchronizing.
Word sync = long time low out
Start of one bit exchange= rise signal.
One unit later change output to desired output.
The slave samples it two time units after start.
The master change to input three time units after start
The slave outputs it«s bit between four and eight time units after start,
else always tri-state.
The master latches it six time units after start.
Twelve time units after start the master change to output again;
outputtinh high if between bits; low if between words.

The slave selects the speed automatically by measuring synk and selecting
timing multiplier from a table of allowed sets.

How about that?

/Morgan
Morgan Olsson, MORGANS REGLERTEKNIK, Sweden, ph: +46 (0)414 70741; fax 70331
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