Catering to the parallel port.....

I don't know, but it will be a risk for your product, if you want to sell it, if you don't use something like USB or ethernet, because new computers don't have a parallel port anymore.

Not for a CNC product. The PP port is very much alive and well there. Most CNC software only supports the PP.

A PCI bus PP card goes for less than $10.00 bucks. Also, there are still computers with PP headers on the motherboard. No, a USB to parallel converter will not work for CNC.

If you don't have absolute control over the interfacing hardware that a customer might use, then going down this route could arise to a support issue one day. How many resistors or problems in board layout is this causing? Or is it a worry with regard to power consumption?

If you are intent in doing this, perhaps you might either cater for an added dil socket in which a resistor pack might be installed (if found necessary) - or have some software detection of an open collector input line so that the user can be informed of incompatible hardware.

I'd just add the pullup's and save it being a future issue.

BTW the following website seems to be a good parallel interfacing reference.

At least Google shows some results for CNC and USB, e.g. this one:

If you are using Windows, you don't have realtime anyway, so it should be no problem to control a CNC machine with USB, if the firmware on the microcontroller side handles the realtime requirements.

Maybe this is true, because of the overhead for translating the parallel port commands to USB and again to a physical parallel port, but a microcontroller with USB support should work.

Leaving logic input pins in an undefined state is never good. Your device might be powered up without being connected to anything, and then what? Also you need to include some sort of protection network on the logic inputs anyway, so it's easy to add pull-up functionality anyway. AoE has a section on logic interfacing.

robert

There's no point. If there is non-zero risk, then include them. It's cheaper than a field failure. ;-)

Do PCs still have parallel ports?

Good Luck! Rich

Not agree>

Your assumption, not the case. Ditto for the rest. You simply do not know enough about the device to make the assumptions you did.

All irrelevant. The device I'm designing is not a CNC controller. I actually know much more about the CNC field than you do. You're not helping at all.

Hence the term "risk management".

So you asked a question that didn't really need answering...

Whatever...

;-)

Depends on what your goal is, which isn't clear.

'Managing risk' to me means 'taking steps to reduce it'.

You seem to be considering a 'calculated risk', designing in a way that'll work, mostly, but not always.

I'd just add high-valued pull-ups to the layout. 22k isn't going to clash with anything.

You don't have to populate them if you really don't want to, and you can solder some in if you didn't, and find they're needed.

All options are then available, for minimal cost.

That's 'managing risk' to me.

Cheers, James Arthur

Then sense it and use the output to enable onboard, diode isolated pull ups. If the port already has pull up resistors, take the termination control line low, and the reverse biased diodes will disable the termination and isolate each I/O pin. If it isn't terminated, take the termination control line high, to turn it on.

If you already know so much why are you here asking questions you don't want answered?

He can know only what you have told him, why are you blaming him for your faults?

Do you always fly with a parachute >

Do you always drone on like a deranged donkey?

No, but when I decide to take a risk I acknowledge it, and I don't use the wrong phrase.

Best, James Arthur

Looking for attention? Ignored you twice already in this thread...Don't feel too bad...Honestly, I have no time for clueless twits like you. Maybe another time.