Parallel port VIs apparently not opening the port

[verdurin]

I used the two NI-provided examples, having checked I was using the correct port address and even using different BIOS settings for the parallel port, but in no case did there seem to be any activity on the port, as checked by PortMon.

[K C]

Hi,

I don't know which examples you use, so I can't comment on that.

See attached VI It writes data to port 0x378 (standard parallel port) Data is inverted every cycle.

This should toggle all the data bits.

I don't if a software tool like portmon will see this. You have to check the data bits on the connector.

What can go wrong:

Your PC port address for the parallel port is different. Not likely, but you must be sure.

You are using an old version (before 7) of LabVIEW and/or an old version of the Write port function in combination with XP or NT (assuming you are using Windows)

Let me know what this VI does on your machine.

[verdurin]

KC,

It was the "Parallel Port Read and Write Loop" and "Parallel Port Additional Data Register Inputs" examples.  I'm using LabView 8.2, on Windows.

That VI you kindly sent does seem to work.  While PortMon doesn't see any activity, ther other monitor I'm using (a Java program called Parallel Port Viewer) clearly shows activity on the data pins.

Do you know whether simply setting them like that should create a TTL signal, which is what I need to trigger the shutter I'm using?
Multimeter readings indicate around 4.8V when the data bit is set.

Thanks again,
Adam

[K C]

Hi Adam,

Because of the levels and the long interface lines you should use a buffer IC to get the signals at the right level and to protect the circuits that you want to connect with the parallel port.

You can use a 74LS241 or something like that. It also depends on the levels you need.

[verdurin]

KC,

Just to let you know that I've got this working now.  Part of the problem before was a dodgy cable.  We've made a new one and now triggering the shutter via the parallel port works.

Thanks a lot for your help.

Adam

[K C]

Hi Adam,

Nice to see it's working.