linuxcnc for new setup without a breakout board

[helpmeout]

My Question is this has any one not used a breakout board, but connected the output lines from the parallel port pins no.2,3, 4,5,6,7,or 8,9 for step and direction.I understand the breakout board is used for isolation for protection ofr the parallel port.

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[A_Camera]

My Question is this has any one not used a breakout board, but connected the output lines from the parallel port pins no.2,3, 4,5,6,7,or 8,9 for step and direction.I understand the breakout board is used for isolation for protection ofr the parallel port.

Using a BoB makes the connections easier, so it is not just about isolation and protection, but sure, if you want to eliminate the BoB it isn't a big issue, as long as you know which wire is which. Though, I really don't understand any good reason to skip the BoB. It's a $5 saving unless you plan on buying a very expensive luxury one, so what's the point?

[rodw]

Years ago before we used parallel ports for CNC, I made my own version of a breakout board to control a window display that won me some nice crystal. I didn't know what I had made was a breakout board as Mach3 did not exist back then but with a optoisolator chip, a few resistors and some relays, it was pretty trivial to make. I had 8 outputs each with 2 amps at 12 volts. But today, a BoB would have been so much easier. Don't scrimp on the isolation.

[helpmeout]

The reason im considering this is Im giong to connect the A4988 drivers to some Nema 17 steppers using the parallel ports pins with linuxcnc, if my lap top wont drive the step and direction pins at the correct level thinking of using pull-up resistors tied to the usb for my 5-volts. I suppose i could use some opto-isolators,and that should help.

[A_Camera]

The reason im considering this is Im giong to connect the A4988 drivers to some Nema 17 steppers using the parallel ports pins with linuxcnc, if my lap top wont drive the step and direction pins at the correct level thinking of using pull-up resistors tied to the usb for my 5-volts. I suppose i could use some opto-isolators,and that should help.

I still find no reason to skip the BoB. Perhaps you have space issues, but other than that, I can't think of any good motives. Remember that a BoB is not just an isolator, it also shapes the signals and converts to the right level using Schmitt-triggers, like the 74HC14. It is a much better solution than pull ups or other "self fabricated" solutions which may and may not work reliably.

[rodw]

X2, a good BoB will handle either 3.3v or 5.0 v depending on the PC and do the opto isolation for you. It will achieve what your home grown circuit will achieve and more for little cost. There is no reason to try a DIY approach.