[mmech]

i have bought the http://70.85.87.12/stepper/sp3HT.htm stepper motor package from stepperworld.com and would like to run the controller from my laptop. the problem is my laptop does not have the required 25 pin parallel port. can i use a usb to paralled port adapter to run the controller

http://newsite.pagecomputers.com/sto...uct%5Fid=15616

http://www.usbgear.com/USBG-4-DOC-1....+adapter&hl=en

[DareBee]

I cannot directly answer this question but when I upgraded my laptop and lost my serial port, I used a similar device to be able to DNC my machining centre. Had no trouble at all, just had to install a driver and assign a COM port number.

[DieGuy]

Using a usb to parallel adapter won't work. THe PC parallel port must be directly addressable by the CPU. For a printer this is not critical, but for CNC control the timings coming out of the parallel port is directly needed by the CNC controller. THe usb to parallel conversion is generally buffered and timing is not a consideration.

THe new Gecko rabbit based external CPU may be a solution to this problem though and the performance sounds like it will be lots better than the parallel port step generation.

[ger21]

THe new Gecko rabbit based external CPU may be a solution to this problem though and the performance sounds like it will be lots better than the parallel port step generation.

But it will be ~$500-$800 dollars with Mach4. It may be less, but I believe these are the numbers I've seen estimated.

[DieGuy]

But it will be ~$500-$800 dollars with Mach4. It may be less, but I believe these are the numbers I've seen estimated.

no such thing as a free lunch! The performance enhancement may be worth it and Art has said that owners of MAch 2/3 will get a steep discount, I have heard numbers like $300 for exisitng license holders but that is certainly speculation until hard prices are set. It may well be worth it to get a higher frequency step train. I keep hearing frequencies like 200Khz vs normal Mach 2/3 frequencies of 25Khz.

[ger21]

I think it's 4 Mhz x 6 axis. As for the steep discount, I think it will be the $149 you paid for Mach3.

[DieGuy]

Well of course 4Mhz for a stepper system would be a huge improvement over the 25Khz parallel port systems but are those frequencies practical. Probably not unless your microstepping ratio goes up a like amount.

[ger21]

It let's you use much higher resolution encoders with servos. Now most guys use 250cpr encoders due to the parallel port limitations.

[mmech]

i hoping someone will come along and say "yes". is anybody else sure it will not work. for convenience sake running the stepperworld controller of my laptop would be the best.

[ger21]

It won't work.

[abasir]

USB-to-parallel will not work. I've bought one, tried it, hacked it everyway I could with no success. If you still want to use the laptop, get the PCMCIA-based parallel port such as at http://www.transdigital.net/

[smarbaga]

usb2 specs are up to 2 megabit data transfer.
a usb to printer port adapter will not work because there is no handshaking between the printer and computer, (ack, etc.).
a dedicated usb breakout box will work, the handshaking signals must be re_directed or assigned to the correponding breakout i/o pins (strobe, ack, etc..)
a usb to zip drive adapter may work, (if there is such a thing) u would want to try one , with the agreement for a refund if it doesn't function as u wish.
a controller minimumlly need only a step and direction line. ( minimum per axis)

[mmech]

the adapter from usb gear says that it is appropriate for printers. isn't a printer just a cnc machine?


http://usbgear.com/computer_cable_de...atid=626%2C106

[abasir]

Yes in a way.
Consider the parallel port as your telephone. Just because you and I each have a phone, that doesn't mean we can communicate... certain standard must be agreed upon (like what language to converse in). CNC machine & printer expect certain way communication to be carried out, and unfortunately, the current standard does not match.

[mmech]

i still have not given up on this (for better or for worse). here is a product i have found that says it is a true parralel port. i don't believe it plugs into a usb port. http://www.transdigital.net/info.htm



the website says

"The Trans PC Card - Universal Parallel Port PCMCIA card.
The card we offer here is a real parallel port, mapped to the standard port I/O addresses. It is driven by Microsft drivers of Windows, so there is no need for additional installation/drivers software. The card shows up in the Device Manger as a parallel port LPT1, LPT2 or LPT3. Therefore it is compatible with all parallel devices which can be driven by the fixed parallel ports of desktop PCs. The card may be used in DOS with provided card enabler or with Linux operating systems. "

[ger21]

A PCMCIA card should work. It works basically the same way a PCI parallel port card does. It's the usb to parallel ones that won't.

[Mariss Freimanis]

It's hopeless to even try. Here's why:

Step pulses have to be timed to sub-microsecond accuracy.

Don't believe it? Try this: 20,000 pulses per second have 50 microseconds of time between pulses (1/20,000 = 0.00005 seconds). 19,999 step pulses per second have 50.0025 microseconds between the pulses. The difference is 2.5 nano-seconds (2.5 billionths of a second). Small time-scales indeed.

USB can have 1,000 microseconds of latency (delay), sometimes much less, sometimes much more. How is this exquisitely sensitive step pulse timing going to be preserved then? Answer: It can't.

Neither you nor your printer much cares if data is delayed anywhere from 1 uS to 1,000 uS. Your step motor drives will care a lot though and they will not run.

Mariss

[eman5oh]

No on the usb port, usb is not a real time interface this is the main reson it will not work. USB processes can be interuppted by other os processes.

[mmech]

i sent this email to the people that make the previously posted card.

"i have a dell inspiron 1000 laptop that i would like to use to run a stepper
motor controller that i bought here http://70.85.87.12/stepper/sp3HT.htm .
my laptop does not come with the 25 pin paralled port that the stepper motor
driver requires. i have been told by a few people that a usb to paralled
port adapter will not work for this application because the timings coming
out of the parallel port are directly needed by the stepper controller. a
usb to parallel conversion is generally buffered and timing is not a
consideration. is this the case with the product you advertise on your
website or will it work for my application?"

and got this response

"Will it work ?
Of course why not.
Our card after installation is fully functional parallel port.

Jerry"

[smarbaga]

with a printer there is no timming it is called handshaking as well as control lines , paper out, printer on line, strobe and others.
it has beena long time since i dabbled into the 8255 chip and printer controle signals, like 1985, oops my age.
if i look at a printer port break out box, i see no timming pulses and i see no timming pulses required for most motor drives as well , just step and direction, i don't know where the timming would come from.
the control lines from the standard printer port used for cnc control are usually used for things like home switchs, drive enable ( inputs to the computer), motor speed, motor on, coolanr , vacuum ( outputs from the computer,
the 8 printer data lines are usually used for step and direction, 1 line per signal times 3 axes = 6 data lines, 8 for 4 axes, the data lines are output only, unless one sets up there printer port to the enhances mode then the data lines can be inputs, this is done in the conputers setup program, at startup.
my question to a usb to parallel port adapter vender would be :
1. will it work with a zip drive ( these are bi-directional )
2. can i return it it if won't work with my drive
3. does it have a vertual port driver included
if you can redirect the printer port via a vertual port driver one might be able to use the data line for step and direction.
and if the cnc software will allow you to use a vertual port driver.
i am still building a cnc so i can't talk about the cnc software to much .
i have written my own controle software in the 80's in 'c' and assembler but the cpu's out today probably have so many features it would take 2 lifetimes to learn half of them.
maybe buy one locally if the answers to the above questions are all yes, and try it..... what have u got to loose ....
i have a usb bi-directional breakout box but i have not tried it with the cnc software that is out there as i an just getting back into microcontroller programming and it is sucking all my spare time
good luck