Parallel PORT issue at boot.

Hello. I have a cnc machine and am trying to use LinuxCNC. But I have a problem with the parallel port.
When starting the pc, at startup the parallel port is in an unknown state. I measured the voltage. The voltage is 3.3 volts.
I tried 3 motherboards. Same problem. Someone has already solved this problem? How?

Thanks.
Regards.

3.3V is a valid output state (high) but in general you cannot depend on parallel
port states to be known and not change during PC startup.

If there is a safety issue caused by these unpredictable output states,
A charge pump (a type of watchdog circuit) can used to prevent
unintentional activation of hardware before Linuxcnc gains control
of the parallel port.

Some breakout boards incorporate this charge pump circuit in their design

Can you send me some link of example?
Something that you know and use.
Thanks.

For starters he sells stuff that that can do every thing a parallel port can, only better (and much much more). But Peter is to polite to push his wares like some salesmen.
I like his 5i25 board, it won't do anything until Linuxcnc starts.

There are a couple of ways to do this with regular parallel port stuff, you can buy a breakout board with a watch dog, charge pump built in, like CNC4PCs C11G, or you could use a more ordinary breakout board that requires an external power source (usually 5v) to power the optos, then just add an external physical enable switch that controls that power source (you must turn it on to enable the board you are the watch dog).

I think 5i25 is pci. But I have i pci express X1
upload.wikimedia.org/wikipedia/commons/0...I_und_PCIe_Slots.jpg
there is something compatible with linuxcnc ?

Or I can use CNC4PCs C11G because fit exactly my needs.
I have 4 axis and the spindle need one ON/OFF output and one 0/10v.
But CNC4PCs C11G is a breckout board and i arleady have a male parallel port connector.
Exists something equivalent that is not a breakout board?

Thanks.
regards

Mesa's 6i25 is the PCIe equivalent of the 5i25
store.mesanet.com/index.php?route=product/product&product_id=58

Maybe we need to know more about your setup to make a better recommendation.

What is the male parallel port connector on (hardware manufacturer and model)?

It's a retrofit from a edingcnc controller, i append the pinout.



I'd prefer to use a mesa board but i need to know something.
6i25 is opto-isolated? At startup the output is Hi-z?
I can use it instead of a photo coupler board to make safe the couplinc pc-machine?
Can be put a pin of mesa board in open collector mode?
And in 0-10 V mode?

A lot of question I know.
Thanks.

I am pretty sure that to get optical isolation and analog out, you would need to add one of the daughter cards for the 6i25.

Is this a machine you are building or retrofitting? If you are trying to connect existing hardware, more than likely it is already isolated. Tell us more about what your hooking up, so we can give you good advice, instead of just guessing.

All of your questions should be answered by reading the manuals for the hardware. (see mesanet.com)

I find my way.
I prefer to build a board by myself.
Thanks to all.