DAB,
you're talking of using a laptop to drive the machine and leave your PC in the house, yes?
I do this with a few adjustments. As the good advice already here notes there's a few things to watch, but the compromise that is a laptop works fine for me and I take it back and forth as needed. I use a buffer between laptop and machine and think I need to optoisolate it too.
The laptop PP can be 5v or 3.3v high, most are 5v (ttl) though. Some drivers can use either, some require 5v, thats specific to your driver card.
More often the problem is not voltage but that parallel ports can source much less current (ma) than 'real' pc's, and not enough to drive the logic of the driver card. That occured with all three (IBM, Tosh, Dell) laptops or recent vintage I tried. If your card doesn't work with a laptop because of insufficient voltage or current source you can put in some kind of buffer between the two to accept the laptop's signal and provide sufficient power to switch the driver logic. the problem is as much to do with the driven device as the laptop, after all the laptop can drive a printer can't it?
Most recent LPT driven printers don't use all the signals/pins a LPT has, including some of those we use (2-9, 10-13 etc). That's driver specific. If you've tried cutting up a few cables you'll have found most printer cables have only 8 to 13 conductors. Some Laptops appear to have some the same setup under an OS too. This can usually be fixed by setting the port type in bios to another Port standard, SPP, bidirectional, EPP, ECP or whatever the bios supports.
Not that it matters with Mach2, TurboCNC uses a motherboard hardware timer to determine its step rates. This varies wildly with different sytems and especially laptops. I have a 166mhz laptop that's slower than a 486 desktop and a 300mhz laptop that I use that is 3 times faster than my P4 3ghz PC...
So, it's a fine idea to use a laptop because they're less prone to dirt etc, easy to walk out the shop with it and you can use it next to the PC or machine while setting up. They're not as robust as a real PC, don't drop it and if paranoid use a seperate power supply too. They can be a problem if the Voltage or Ma sourced isn't enough but you can buffer that. Try to get a Laptop that you can get into the bios and change the parallel port settings on.
Finally a goof on my part blew the parallel port on a laptop, this killed the laptop Motherboard too.. need to optoisolate the current one....  |