True Parallel Port Interface for Bit-banging?

Would that make sense and/or be feasible? Are there better/easier solutions?

Alternatively, does anybody knows if the Parallel Port available thru Laptop docking stations (Dell, HP, Thinkpad, etc.) are True Parallel Ports (ISA compatible)?

Quoted 2 lines

Would that make sense and/or be feasible? Are there better/easier solutions?

Binary patching the DOS application? Port accesses should be easy to find.

Getting a laptop with parallel port via auction site?

Would the ExpressCard Parallel Port appear always at the same address? While this could work, it wouldn't be generic. I would have to do the operation for N apps.

The virtualisation idea is not good then?

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The virtualisation idea is not good then?

It is not that. I think good old DOSEMU could do that. Bit-Banging ports can be timing critical, though, and in this department virtualization solutions often fail.

Or is the "timing issue" you talk about more related to unpredictable latencies due to the way the SW virtualisation works?

What about emulation? Do you think emulation would be more predictable?

Quoted 6 lines · Wolfram Sang

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The virtualisation idea is not good then?

It is not that. I think good old DOSEMU could do that. Bit-Banging ports can be timing critical, though, and in this department virtualization solutions often fail.

Thanks.
I understand your point, but I'm guessing that the big-banging routine (or the protocol to be used) should be time-independent in order to run on different real HW PCs, right? Otherwise a 386DX and a 486DX2 could behave differently, right?

Or is the "timing issue" you talk about more related to unpredictable latencies due to the way the SW virtualisation works?

What about emulation? Do you think emulation would be more predictable?

I have tried dosemu, dosbox and as far I remember also VirtualBox with an old, DOS car service app.
Wasn't able to make it communicate until I booted true DOS. That machine had old-style ISA serial ports so it was possible.

I don't have experience with bit-banging parallel port but I do have some with bit-banging PC serial ports (which should be very similar) and can confirm that old DOS software can be *very* fragile with regard to timing.
I have tried dosemu, dosbox and as far I remember also VirtualBox with an old, DOS car service app.
Wasn't able to make it communicate until I booted true DOS. That machine had old-style ISA serial ports so it was possible.

You also have asked previously whether laptop port would work. On my current HP Elitebook ports of both types are wired to Super IO, and using PC standard IO port and interrupt numbers.

I also remember that at least on ThinkPads and HP Compaqs that I had contact with (these were laptops from 10+ years ago) both serial and parallel ports were wired to Super IO chip (including ones available only via port replicator).
So they were also at PC standard resources.

However, other issue is that sometimes such ports are inactive by default (don't respond) until enabled by PnP.

This is also a problem with PCMCIA cards - they are disabled by default.

I have Argosy 2xRS232 PCMCIA card and remember it came with DOS driver which could enable them on I/O port close to standard one - this was one of their major selling points.
So your ExpressCard would probably need similar software.

Quoted 10 lines · Maciej S. Szmigiero

I don't have experience with bit-banging parallel port but I do have some with bit-banging PC serial ports (which should be very similar) and can confirm that old DOS software can be *very* fragile with regard to timing.
I have tried dosemu, dosbox and as far I remember also VirtualBox with an old, DOS car service app.
Wasn't able to make it communicate until I booted true DOS. That machine had old-style ISA serial ports so it was possible.

Thanks for sharing your experience.
I think it should be related to the latencies Wolfram discussed.

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You also have asked previously whether laptop port would work. On my current HP Elitebook ports of both types are wired to Super IO, and using PC standard IO port and interrupt numbers.

Would you mind sharing the laptop's model?

There are a bunch of
Elitebooks and maybe not all have the ports wired.
Does your laptop has the Parallel Port on the docking or on the laptop itself?

Quoted 6 lines

I also remember that at least on ThinkPads and HP Compaqs that I had contact with (these were laptops from 10+ years ago) both serial and parallel ports were wired to Super IO chip (including ones available only via port replicator).
So they were also at PC standard resources.

Yes, it appears that Thinkad T42 could work:

https://forum.linuxcnc.org/forum/49-basic-configuration/15999-thinkpad-t42-parallel-port-not-working

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However, other issue is that sometimes such ports are inactive by default (don't respond) until enabled by PnP.

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This is also a problem with PCMCIA cards - they are disabled by default.

Do you know the command to enable them thru PnP? Shouldn't loading the kernel module be enough? Or is it the other way around and enabling thru PnP triggers the kernel module load process?

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I have Argosy 2xRS232 PCMCIA card and remember it came with DOS driver which could enable them on I/O port close to standard one - this was one of their major selling points.
So your ExpressCard would probably need similar software.

Thanks for the pointer.

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Would you mind sharing the laptop's model?

This is Elitebook model 8570p.

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There are a bunch of
Elitebooks and maybe not all have the ports wired.
Does your laptop has the Parallel Port on the docking or on the laptop itself?

Only a serial port socket is built-it, parallel port socket is available only via a port replicator.

According to description of this replicator it is compatible with a lot of different Elitebooks and Probooks:
http://h30094.www3.hp.com/product.aspx?sku=10432928&mfg_part=A7E34AA&pagemode=ca

I wasn't able find any note in this replicator description that port availability depends on connected laptop model.
You can try to search for particular laptop model schematics, even if it is available only for sale sometimes there is a preview page with block diagram which clearly show where the parallel port is connected (this is true for my laptop model for example).

However, whether the port is on standard I/O address and interrupt line requires some more digging.

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Do you know the command to enable them thru PnP? Shouldn't loading the kernel module be enough? Or is it the other way around and enabling thru PnP triggers the kernel module load process?

If you want to use them under Linux then everything should be taken care of by kernel's PnP support.
It can be problem if you want to use them under pure DOS.

Quoted 3 lines · Maciej S. Szmigiero

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Would you mind sharing the laptop's model?

This is Elitebook model 8570p.

That seems like a fairly recent laptop:

http://www.notebookcheck.net/Review-HP-EliteBook-8570p-B6Q03EA-ABD-Notebook.82291.0.html

and it has a true parallel port?

Thanks a lot for the pointer!

Alternatively, does anybody knows if the Parallel Port available thru Laptop docking stations (Dell, HP, Thinkpad, etc.) are True Parallel Ports (ISA compatible)?

Quoted 3 lines · Sebastian Frias

Alternatively, does anybody knows if the Parallel Port available thru Laptop docking stations (Dell, HP, Thinkpad, etc.) are True Parallel Ports (ISA compatible)?

Some laptops such as the ThinkPad T42 had parallel ports, without the need of a docking station. I know because my dad still has one. But well these are 2004 machines, may be hard to find these days.