Re: wonderboard

>
> From: "Harrison, Doug" <dharrison@...>

Marc;

> If I understand correctly, your vision of wonderboard included the ability
> to use it for a variety of applications outside of the original scope.

Keeping things simple open and based on a common starting point to allow
expandability and common software libraries that are open to new features and
uses is not a good goal?

I am not an electronics expert.
What I know is from playing around for the most part.

> This
> was to provide a bonehead simple means of interfacing the parallel port to
> step drivers, limit switches and four general outputs.

Perhaps my general description, and your admitted lack of understanding of
digital electronics stand in the way, Maybe you envision something more
when I say "Buffer" or "Latch" than a simple TTL Device.

This IS "Bonehead Simple".

Maybe the use of one of the extra outputs from the parallel port and a
specific example will help:

Use these pins from tha parallel port.
Pin Name.
1 strobe (Output)
2 data 0 (Input/Output)
3 data 1 (Input/Output)
4 data 2 (Input/Output)
5 data 3 (Input/Output)
6 data 4 (Input/Output)
7 data 5 (Input/Output)
8 data 6 (Input/Output)
9 data 7 (Input/Output)

12 Busy (INPUT)
16 Read-Write 1 Read 0 Write (Output)
17 Data-Address 1 Addr 0 Data (Output)



Now, DATA 0 - DATA 7 are the data bus.

DATA-ADDRESS will activate either the "Address Latch Chip" or One of the
Many "Xcvr Chips" connected to the devices, ie. Stepper or sense switches.
"0" is the devices, "1" is the "Address Latch Chip".

READ-WRITE is used only for the device access. "1" makes The "Xcvr Chips" send the
outside data to the "DATA BUS". "0" Makes them latch the data on the "DATA BUS"
into the outputs, stuff like the drivers for the Steppers.

The address works like this...
You set the "DATA-ADDRESS" bit to "1"
Write the address, say 3.
This will latch 3 into the "Address Latch Chip".
That Chip is connected to a "3 to 8 decoder".
Line 3 of that chip will come high and activate "Xcvr Chip #3"

Now Reading from or writing to the printer port will either
read from or write to the devices or switches connected to that
chip.

Not rocket science.

At a minimum you would need 3 chips.

Without adding an additional decoder you could run 8 "Xcvrs Chips"
or 64 bits of I/O.
All the "Xcvrs Chips" would be wired in parallel except for one
pin which would be connected to one of the 8 pins on the "3 to 8 decoder".
This make it dirt simple to design and build as well.

A Full 64 Bit Interface would take all of 10 TTL ICs, (The 16 pin
5 for a buck type).
Adding Opto-Isolators, Relays or LEDs would also be required for
many uses, but that depends entirely on the intended use.

I could have drawn it faster than it took to explain it, but not in ASCII.

Marc