Any clues on my LPT woes?

[Greolt]

Been running Mach3 on my laptop via a buffered, not optoisolated, BOB.

Quite successfull, no problems.

Now as per prevailing opinion I have hooked up a desktop with on board LPT. 1.67 ghz 368 mb

Same version of Mach, same xml, same printer cable. Ports and Pins still correct.

But it is just not getting any signal from my homing and limit switches.

Doesn't matter if active low or high. Motors run fine on jog so its not port assignment issue.

Any clues???

[nickwass]

I'm no expert and you're probably aware that some parallel ports are not bidirectional. Also, it may be that the port does support input but the BIOS settings are incorrect. My limited knowledge is based on "How to interface PC's" by RA Penfold, ISBN 0-85934-467-3.

N.

[Greolt]

Thankyou Nickwass.

I was ignorant of the different LPT modes so did some googling and learned a bit

Laptop was ECP and desktop that worked was ECP too.

Tried all the options given in Bios and still no different. NORMAL, EPP, ECP- DMA3, EPP+ECP

Looks as if I have a sus mother board.

Bring on the ncPOD I say !!!!!!!

[NC Cams]

Assuming the LPT port is not DOA, did you investigate the signal voltage output levels?

Some LPT's work on low power (about 3.5vdc HIGH) and others are the more conventional digital signal (5vdc HIGH). A lo power output MAY drive a conventional device but not always.

This problem that you're encountering is another reason why laptops are not the preferred item to use with Mach - they don't always work and no two that do not work respond to the same fixes.

[fyffe555]

you might want to check the lpt port address is the same also, or that it matches what mach3 is talking to. its a long long shot but.

[Halfnutz]

Also check your logic levels to the drives and inputs. For every active high on that LPT the +5 voltage drops a percentage At some point the +5V ends actually too low to trigger an input to the controller and eractic or no behavior begins, for no apparent reason.

I have had a bunch of issues like that and now I allways use a breakout board with seperate power supply or like today, I added two inputs and had to pull them up with +5V and a 1K resistor. It just wouldn't work without them.

[pminmo]

A couple of things that could be an issue. Just because one machine worked in ecp mode, doen't mean the other one will. There are 7 ecp modes. If you use the machines parallel port for nothing else, set it to SPP in the bios settings. WinXP will use the bios settings. The other as per the above replies is does the breakout board have pull up resistors to 5V? If not you will probably have to add them.

[Greolt]

Originally Posted by NC Cams This problem that you're encountering is another reason why laptops are not the preferred item to use with Mach .....................

The laptop works. The desktop is the problem.

[Greolt]

Hey I really appreciate all you blokes (Australian for Guys) taking the time to respond to my post.

I got a PCI parrallel card and gave it a try. It is PPP type. Worked fine. Read all my switches. Ran the motors sweet.

Funny thing now is I must unplug the Parrallel cable from the machine or the computer hangs mid boot up.

If unplugged it boots fine. If plugged in it hangs.

[ger21]

maybe a hardawe conflict. You might try disabling the onboard port in the bios and see if it helps.

[Greolt]

Gerry tried what you said. No go.

Tried another IRQ. No go.

I'm sure this glitch with the PCI card could be tracked down with enough persistance but I'm not that desparate.

I have come to the conclusion with the cranky on board LPT that the mother board is sus.

I only tried this desktop because of so many posts saying don't use a laptop. Thought I'd give it a whirl.

However I'm going to stay with the laptop for now because it works despite others experience.

Having said that I'm going to be an early adopter when the ncPOD comes on board. Looks to be the future for blokes like me.

Anyway thanks again all for your tips.