Mach & PCI Parallel Port

[JeLC]

Will the Mach3 printer port driver test run the speed test on a third party PCI parallel port? I have one ordered to see if it will solve a 'step loss' problem I've got on my machine. Don't know, but seem to remember in one of the Mach3 tutorial videos that it will only test the built in port on the motherboard.

[ger21]

It should work with any parallel port, either built in or PCI.

[shae marks]

'step loss' problem

What is step loss problem..

Regards


shae marks

[mcphill]

Will NOT work with USB based Parallel Port replicators! These only work for printers.

[JeLC]

Originally Posted by shae marks What is step loss problem.. Regards shae marks

While I'm no expert, and hopefully someone will correct me if I'm wrong, losing steps happens when the computer cannot generate step pulses fast enough to keep the stepper motors accurate.

In other words, Mach3 sends an interrupt request to the CPU requesting processor time to generate a step pulse. The CPU must finish what it is doing (reading the keyboard, mouse, refreshing the screen, etc) and then responds back to Mach that it can now honor the request. Some systems, mine for example, take too long for the CPU to actually generate the pulse and deliver that pulse to the motor(s).

I'm running a 2.4Ghz system, so the speed of the processor doesn't necessarily mean that a computer is a good candidate for running a CNC system. Unfortunately, I seem to have one of those. I've been chasing this problem for about a month now and have just about run out of options.

[ger21]

Have you gone through the optimization list?

Is it a dual core processor?

[Torchhead]

Very few processes preempt the MACH pulse engine (which is the core reason MACH can get 100,000 PPS out of a PC). The keyboard and mouse access are not processes that would cause problems unless you were trying to run the PC as a controller and running Word or Outlook too and writing a novel!

. Typically it has to do with ring zero processes of which hig speed communications is one. If you have a process running in the background stealing cpu cycles it can cause pulse stream "stutters". If that process is trying to talk to an output port (i.e. ethernet or parallel port) then it will preempt MACH. One trick if you are running with an enabled NIC in Windows is to make sure the card is not set to "auto" on speed (usually in the Advanced setup section). It polls the hub to negotiate speeds and that eats cycles. If no hub is there it keeps trying. Either disable the NIC or if you need it then make sure the speeds are set to what you are using (10 or 100 MHZ).

Another source of timing issues is with on-board video. Sometimes turning off toolpath generation will help. Sometimes you have to switch to using a plug-in video card with it's own memory.

There are issues with dual core machines.

I find a used Pentium 4 (or AMD equiv) running XP with 512 RMA and a 2.4 GHZ processor in a desktop and on-board or PCI expansion parallel port lets us run at 60.000 PPS with no loss of position. I have been buying re-conditoned machines WITH XP pro (HP's and Compaqs) installed and 1G ram with 2.6 and 2.8 processors, keyboard and mouse for $179.00. They have parallel and serial ports and internal ethernet. So far the on-board video has not caused us problems but there are two PIC slots open if needed + an AGP slot.

"lost" steps are not always a pulse problem. We have stepper based systems with MACH that have never lost a step in over a year of production. We tune them conservatively and don't try to push their torque limits with over aggressive cutting.

TOM Caudle
www.CandCNC.com

[nenetwork]

Try the optimisation list, that fixes 90% of the problems.