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The PC's parallel port can be used to perform some very amusing hardware interfacing experiments. The port is very easy to use when you first understand some basic tricks. This document tries to show those tricks in easy to understand way. PC parallel port can be damaged quite easily if you make mistakes in the circuits you connect to it.
If the parallel port is integrated to the motherboard like in many new computers repairing damaged parallel port may be expensive in many cases it it is cheaper to replace the whole motherborard than repair that port.
If you manage to damage the parallel port on that card, replacing it is easy and inexpensive. The programming examples do not work with USB to parallel port adapters they use entirely different hardware, their drivers make them to look like normal parallel port to operating system "normal" applications.
Every reasonable care has been taken in producing this information. However, the author can accept no responsibility for any effect that this information has on your equipment or any results of the use of this information. It is the responsibly of the end user to determine fitness for use for any particular purpose.
The circuits and software shown here are for non commercial use without consent from the author. How to connect circuits to parallel port PC parallel port is 25 pin D-shaped female connector in the back of the computer. It is normally used for connecting computer to printer, but many other types of hardware for that port is available today.
Not all 25 are needed always. Usually you can easily do with only 8 output pins data lines and signal ground. I have presented those pins in the table below.
Those output pins are adequate for many purposes.
Those datapins are TTL level output pins. In real world the voltages can be something different from ideal when the circuit is loaded.
The output current capacity of the parallel port is limited to only few milliamperes. Here is a simple idea how you can connect load to a PC parallel port data pins.
The parallel port data pins are TTL outputs, that can both sink and source current. This is called a "totem pole output". At any given time one of these transistors is conducting and the other is not. Simple current sinking load connection: Trying to toke too much current for example shorting pins to ground can fry the parallel port.
I have not killed any parallel port yet in this method, but I have had in cases where too much load has made the parallel port IC very hot. This can be made with a circuit like this: This circuit gives you capability of of driving more current than the "sinking" approach.
You need to be careful with this circuit, because with this circuit you can easily fry the parallel port if you do things wrong.
I have used mostly "sinking" type circuits and this article is concentrated on using them. The only components needed are one LED and one ohm resistors. You simply connect the diode and resistor in series.
The resistors is needed to limit the current taken from parallel port to a value which light up acceptably normal LEDs and is still safe value not overloading the parallel port chip. In practical case the output current will be few milliampres for the LED, which will cause a typical LED to somewhat light up visibly, but not get the full brigtness.
Then you connect the circuit to the parallel port so that one end of the circuit goes to one data pin that one you with to use for controlling that LED and another one goes to any of the ground pins.
Be sure to fit the circuit so that the LED positive lead the longer one goes to the datapin. If you put the led in the wrong way, it will not light in any condition.Detailed Description.
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The Control Port (base address + 2) in intended as a write only port. When a printer is attached to the Parallel Port, four "controls" are used. The most common AutoCAD format is the "drawing" format, with a file extension ending monstermanfilm.com Few software applications can read this format, which is the default when saving files in AutoCAD.
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