How to send a signal from PC to a circuit board?

How about using the parallel port? At least 8 easy to use data lines. Real easy if you are using Win98 or less or DOS. Win2K and XP are a little tougher.

Jim

I am using Win XP. How hard would that be?

You will need one of the VXD's that allow you to access the parallel port hardware. XP blocks applications from doing that.

See:

Among others. I'm sure others here know of more drivers.

Jim

It adds an extra layer of complexity. After Win98, the user is not allowed direct access to hardware, including I/O ports.

Someone here previously mentioned two ring 0 device drivers called GiveIO and UserPort; I bookmarked the following site to d/l them, but have not used either, since I use some old PC's and win9x for I/O stuff.

Maybe you should find an old PII/PIII machine and someone's old win9x CD as a test machine; it could save your main machine if you short something...

HTH

*Easy* ? I wouldn't call it easy myself.

Graham

I used a parallel port to drive an lcd for an old school project. You need to look-up what address the port is located at, how you can get the port to automatically latch the data and a way to get access to the I/O pins directly. For the last part I use a c compiler called djgpp that makes a dos executable that can have direct access to the I/O pins. I think I used simple in(address) and out(data, address) commands to communicat but you'll have to look those up to be sure. Note that these functions are in a special library.

---Matthew Hicks

Still won't work under XP without using a VXD.

Google inpout

The easiest way to do this is to scrounge an old PC with DOS, and use QBASIC to address the 8 data bits of the printer I/O port. Make sure the printer port is configured in BIOS as SPP. No extra hardware required if your decoder accepts TTL signals. Your most time consuming activity will be making the connector for the DB25 plug.

Cheers Chris

If you run userport (google for userport.zip) you can get user level hardware access on XP machines. Once you have user level accrss, you probably can do the rest of your programming using notepad. I've got a couple of pages below with some simple parallel port I/O setups.

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It very much depends on the specific LCD panel you want to work with.

If you have a specific panel in mind, you can search on the model number for a datasheet.

If not, HD44780-based character displays are popular (and cheap):

USB driven LCD project:

HTH

Whoever supplied the LCD should have technical documentation.

And please learn to trim and bottom post.

Good Luck! Rich

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LCD should have technical documentation.

The LCD is going to be fabricated by myself. It will have 16 rows and

16 columns driven by two 4-to-16 decoders. The parallel port will be used to send two 4-bit signals to control the decoders.

Basically, I need a way to turn on/off the 8 output pins of the parallel port in WinXP. A good webpage I found is

This shows a relay controlling circuit that can protect your parallel port from voltage spikes. Anybody knows a way to do this without using a relay coil.

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[snip]

If you're interfacing with another 5v circuit, just use a protective resistor (say, 300 ohms) to the parport pin.

Don't forget to connect the parport ground to the circuit ground!

+5v | ___ |\\ o-|___|--| >O- o R |/ | | === === GND GND (created by AACircuit v1.28 beta 10/06/04

For other DC circuits, the simplest safe way is with a transistor switch. Resistor R is connected to the parport pin, and GND is common to both the parport ground and supply voltage ground. When the parport pin goes high, the load is switched on.

The advantage is that +V can be something other than 5v, i.e. 12v.

+V | o Load o | ___ |/ 0---|___|--| R |> 0 | | | === === GND GND (created by AACircuit v1.28 beta 10/06/04