Isolation board between parport and driver board

Hi I am trying to build an connection board between parport and driver board for an old robot.
I thought some optocouplers would be a good idea to isolate the two circuits.

Although I noticed that inputs of driver board have got pull up and pull down resistors .

After some research I found that this is an obsolete termination. Also there are some diodes which are confusing me!

I am wondering how may achieve the connection with the optocouplers
May I use this termination as a pull up resistor like this ?

Thank you in advance!

That termination is not obsolete; in fact is is a quite clever method to ensure that the status of the pins is possibly preserved when somebody pulls the cable. The designer probably thought that was necessary, otherwise he would have used pulldowns.
The diodes are there for extra ESD protection.

For the optocouplers you need another pullup from the collector to the 5V. If you want any speed, you need to make this a fairly low value, but not low enough to cause problems with a lower CTR value of the optocoupler. If the CTR is around 50%, you might want to try 2k2 or so.

I would also put a resistor and capacitor in parallel, and put that in series with the optocoupler LED. 680Ohm parallelled to 1nF or so will do; any lower resistor value and you are stressing the weak moden parallel port outputs. If the parallel port is an older one you might want to lower the resistor to 330 Ohms or so to gain some speed.

Thank you!

Indeed, the termination is not obsolete at all. You cannot trust Greek forums

The driver's input can read Low (L) when the signal is low?

Should i need to interpolate a NOT gate between the optocoupler and the driver's input pin?

I am little clumsy with the terminology. i hope, I am understandable

Best regards!

If the input of your robotics board is low (<0,8V), it will be registered as a low. If it is high (>2,0V) it wil be registered as a high. That said: the input configuration on this board indeed does not make sense; without input the input is pulled to Vdd/2=2,5V, which is registered as a 'high'. And using 10k resistors to terminate a transmission line or to balance delivered current by the parallel port output in order to equalize delays makes no sense either.

The optocoupler you chose is not the most ideal one if you need to drive it directly from a modern parallel port since it prefers 10mA+ of LED current. Something a modern LPT cannot provide (~4mA). I would add a buffer between the LPT and optocoupler LED. Simple NPN transistors, a 74244 buffer, whatever suits you.

In hindsight, a better conenection for the optocoupler transistor is collector->5V on robot board, emitter->input, pulldown resistor between input and GND. No need for inverters; if you have to swap polarity you can do so by configuring LinuxCNC.