Re: [CAD_CAM_EDM_DRO] Re: Compters without printer port

Stephen Wille Padnos wrote:

>>> I had that same problem with XP(I also had it when I tried Win2K) that the PC would not boot up if the parallel ports were plugged in to the breakout boards.
>>>
>>> I was beginning to think I was crazy, as I reported it on the Mach forum, and nobody seemed to have ever heard or seen anything like it before.

>> with such a problem, the reason may be that the BOB (or equivalent) is drawing far too much current from the individual pins. The boot up check is seeing this and for safety reasons its stopping the boot.
>> I know its a fiddle, but you need to measure the current drawn when a pin is activated, not that easy.
>> The printer port guarantees only a max of 2.6 ma as a source or 24 ma as a sink (7400 specs). That means that on a BOB with Opto isolation for example that the input resistors need to be around 2K Ohms minimum. More is OK.... I have seen preofessional BOBs with only 370 Ohms...470 Ohms is typical and completely wrong....
>> Join DIY-CNC-Interfacing if you wish and read more about this. Also the printer port specs are there to read too....
>> If you draw too much current, you could even damage the Printer Port (which is buried in a BIG chip that has many functions other than Printing), or even the mainboard itself. Be carefull.....

> The most likely explanation to me is that the BOB looks like some sort
> of EPP or ECP device, but when the driver can't get it to reset or
> initialize, it disables the port. This might make sense when the
> expected use of a parallel port is to communicate with things like
> printers and scanners. It may also be an issue if the thing connected
> to the interrupt input is in the "wrong" state while Windows is booting.

Certainly in my own case, the BOB is specifically deigned to draw almost no
current. Some breakout boards that hang opto isolators directly on the parallel
port will not work with ITX and other 'set top' style motherboards, so I've gone
for a low current buffer as the very first stage.

The fact that W2k boots fine and XP doesn't point to an initialization problem
with windows rather than any hardware problem. ANd as I say - leave the cable
out - start XP - plug in. Then no problem either.

--
Lester Caine - G8HFL
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