Using Printer port for input signals

[buddhika]

Are there anyone who can help us with using LPT printer port for getting input signals to PC???
Or any trusted website for info?

1 HOw do we use 10-17 pins to send in a signal by the printer port ? ( how to apply the voltage and how much voltage)

2 Are we to use (redirect) ports own voltage for that??? or apply outer volt?

Thanks

 

[blahblah99]

Originally posted by: buddhika
Are there anyone who can help us with using LPT printer port for getting input signals to PC???
Or any trusted website for info?

1 HOw do we use 10-17 pins to send in a signal by the printer port ? ( how to apply the voltage and how much voltage)

2 Are we to use (redirect) ports own voltage for that??? or apply outer volt?

Thanks

Go here, under legacy ports.

 

[buddhika]

Thanks for your comment.

I have the info about which pin can send signal in and which out but the problem is how to apply a voltage. I want comment from a one who have practically done this.

Do i have to use a voltage from out side or switch the printer ports own voltage???

 

[harrkev]

You can feed a signal back into the PC from an outside source. The best bet is to use old 5V TTL stuff. 74 LS series stuff works great.

Note that the software to do this is NOT easy under Windows XP. The problem is that the hardware registters are considered to be under the care of the kernel. You need a special driver to directly access the hardware in XP or NT.

It is much easier under DOS, and the DOS-like Windows (3.1, 3.11, 95, 98, ME). Set a pointer to the I/O address and rock.

**EDIT** Be sure that you set up the port right. These things default to being driven. You have to set the data lines to be in inputs in software. If you don't do this, or if you plug in your calbe BEFORE turning on the software, you can blow some output transistors.
My recomendation is to use one of the dedicated output pins (such as the form-feed line) to the enable line of the output buffer of your circuit. Power on the computer and measure the voltage of that line, and use that level as the "disable" level. That way, your software can toggle that line and enable the buffers AFTER it has set the data lines to receive.

I hope that my explanation is clear.