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Catering to the parallel port.....

I started this thread in the basics newsgroup but the issue is really
one of risk management at the design stage. Given that the data lines
of today's PC parallel port seldom ever uses open collector ouputs
(with no internal pull-up resistor) anymore, wouldn't it be a prudent
risk to not include pull-up resistors on the data lines in a device
that will interface with the PP?
 
F

Frank Buss

Jan 1, 1970
0
I started this thread in the basics newsgroup but the issue is really
one of risk management at the design stage. Given that the data lines
of today's PC parallel port seldom ever uses open collector ouputs
(with no internal pull-up resistor) anymore, wouldn't it be a prudent
risk to not include pull-up resistors on the data lines in a device
that will interface with the PP?

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.
 
but it will be a risk for your product

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.
 
A

Adrian C

Jan 1, 1970
0
I started this thread in the basics newsgroup but the issue is really
one of risk management at the design stage. Given that the data lines
of today's PC parallel port seldom ever uses open collector ouputs
(with no internal pull-up resistor) anymore, wouldn't it be a prudent
risk to not include pull-up resistors on the data lines in a device
that will interface with the PP?

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.
<http://www.beyondlogic.org/spp/parallel.htm>
 
F

Frank Buss

Jan 1, 1970
0
Not for a CNC product. The PP port is very much alive and well there.
Most CNC software only supports the PP.

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

http://www.majosoft.com/engraving/html/usb_cnc_on_winxp.html

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.
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.

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.
 
R

Rich Grise

Jan 1, 1970
0
I started this thread in the basics newsgroup but the issue is really one
of risk management at the design stage. Given that the data lines of
today's PC parallel port seldom ever uses open collector ouputs (with no
internal pull-up resistor) anymore, wouldn't it be a prudent risk to not
include pull-up resistors on the data lines in a device that will
interface with the PP?

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
 
If there is non-zero risk, then include them.

Not agreeing that one should always design for zero risk but what
value would you use, bearing in mind that it will be in parallel with
any pull-ups already on the PP and would be the only pull-ups in the
case of OC outputs?
 
Leaving logic input pins in an undefined state is never good.

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

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.
 
J

James Arthur

Jan 1, 1970
0
I started this thread in the basics newsgroup but the issue is really
one of risk management at the design stage. Given that the data lines
of today's PC parallel port seldom ever uses open collector ouputs
(with no internal pull-up resistor) anymore, wouldn't it be a prudent
risk to not include pull-up resistors on the data lines in a device
that will interface with the PP?

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
 
J

Jasen Betts

Jan 1, 1970
0
Your assumption, not the case. Ditto for the rest. You simply do not
know enough about the device to make the assumptions you did.

He can know only what you have told him, why are you blaming him
for your faults?
 
'Managing risk' to me means 'taking steps to reduce it'.

Do you always fly with a parachute in your hand luggage? Do you wear
goggles when driving in a convertible with the roof down? Do you
always wear gloves? Are high rise buildings and bridges designed to
withstand the highest richter scale reading in earthquake prone
regions?
 
J

James Arthur

Jan 1, 1970
0
(un-top posted)

Do you always fly with a parachute in your hand luggage? Do you wear
goggles when driving in a convertible with the roof down? Do you
always wear gloves? Are high rise buildings and bridges designed to
withstand the highest richter scale reading in earthquake prone
regions?

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

Best,
James Arthur
 
Do you always drone on like a deranged donkey?

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

You've guessed one aspect of risk management. Other aspects still
elude you. Should I enlighten you?...Nah!...You got enough clues
already....Stay in the dark.
 
B

Ben Bradley

Jan 1, 1970
0
Not agreeing that one should always design for zero risk but what
value would you use, bearing in mind that it will be in parallel with
any pull-ups already on the PP and would be the only pull-ups in the
case of OC outputs?

After reading your other responses in this thread, I'd strongly
recommend using a resistance value no higher than 2.2 ohms, or no
lower than 22 megohms.
 
J

James Arthur

Jan 1, 1970
0
You've guessed one aspect of risk management. Other aspects still
elude you. Should I enlighten you?...Nah!...You got enough clues
already....Stay in the dark.


You write poorly, beg us for help, and abuse those who try.
You're wrong[1], you're rude, and you top-post. You've
gotten several good suggestions and you've cast them aside.

Enlighten me? What could you possibly offer me?

Go ask your basic question in .basics, if they'll have you.

James Arthur
~~~~~~~
[1] http://en.wikipedia.org/wiki/Risk_management
"The objective of risk management is to reduce different
risks..."
 
R

Robert Latest

Jan 1, 1970
0
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.

Here's someone who's keen on learning just how a community works.

Since you know the different specs of the different types of ports that
your device might be connected to, just use a resistance value that
works with all of them. If that can't be done because some
configurations are mutually exclusive, you will have to specify which
type of port your gadget is compatible with.

What's so hard about that?

robert
 
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