Simple EPP IO board

Hello...

As my machine happily run under EMC and parport driver now I'm runing out of pins.
Currently I have 3x3 pins to control 3 steppers (custom design with strange 3 wire interface) based on linisteper. Work perfect in halfstep/full torq with my 3V 3A steppers. It has power save function too (after 1 sec no moving the current is halved). Next I have spindle output relay with chargepump and chargepump enable all signal. Few limit and home switches and there are no free pins left. .. and as I use laptop there is no way to add another lpt. And of course all things is opticaly isolated from pc.

So as I want to extend this to one more motors (like to have two bipod for foam cutter) I'm in stage of designing board. For now I'm planed.

4 relays 10A/240V AC (all 4 operates as chargepump so false triger is not likely)
20 Digital outputs can be extended (up to 72 is possible but that's owerkill for software stepgen)
16 Digital input's can be extended (up to 80 but that's too is overkill for software stepgen)
EPP interface side opticaly isolated from other components. (20 cheap optocoupler's needed instead at least 32 if output side is isolated)
Material cost should be under 25Euro.

Software interface very simple and fast. As I study driver the IO is done in one place and all bits is output at one sub.
So my plan is to
EPP WRITE ADDRES as byte 0 (relays
EPP WRITE DATA as byte 1 (1'st 8 lines)
EPP WRITE DATA as byte 2 (2'nd 8 lines)
EPP WRITE DATA as byte 2 (3'rd 8 lines)
.. .. .. up to 9 writes (total 10 bytes)

and for read similar
EPP READ ADDRES (read 1'st 8 lines)
EPP READ DATA (read 2'nd 8 lines)
EPP READ DATA (read 3'rd 8 lines)
... ... up to 10 bytes possible

Very simple and low overhead.

The board has only digital logic. No PLD's No CPU's Just Optocouplers 74HC4017, 74HC00, 74HC14,74HC573 and few discrete components.

Someone interested?

Slavko.

p.s.
I don't want to sell. When done all design will be posted on forum for free.

Schematics - pre - alpha

I'm updated wishlist...

The board has 24 outputs (4 has relay's connected)
and also 24 inputs. It's came out pretty big 140mm x 185mm.
It's drawn as doublesided but all thing in top layer can be replaced by wires.

So now is the time to make that gizmo...

The board is drilled.....

The board is etched

Population of board before shoping.... .. that I have laying around

BigJohnT wrote:

Cool. How did you etch the board?

John

Just google for toner transfer method for making PCB.

I simple therm....
I print image with laser printer onto "special" paper (.. onto stuff I found in my mailbox as advertisments)
I laminate that with modified office laminator onto cooper clad.
.. soak in hot watter few minutes
.. pell off paper
.. etch.. (I use 1/3 H2O, 1/3 HCL, 1/3 H2O2) in smallest possible quantity. (just to cover PCB while etching)

.... as usual 1'st board has few mistakes. So here is new schematic and board layout. Now the Board is tested. It's works as should be. Now need the time/knowledge to write driver.
For now I just rumbled in emc sources and get very confused... C is realy not my language