Parallel Port Interfacing, DevPascal Programming and Example Projects

Transcription

1 Parallel Port Interfacing, DevPascal Programming and Example Projects By: Depayne Athia Cooperative Education Class of 10

2 Parallel Port Interfacing What is a DB-25 Parallel Port? The DB-25 Parallel Port, in most basic terms, is the old 28-pin port standard for peripherals such as printers. It is like the USB port of the past. For our purposes, it will be used as a communication gateway between a device that we create, and a program that executes instructions. The programming part will be focused later on in this tutorial so don t worry. Figure 1 This is what the parallel port looks like

3 Okay, so how does this complicated concept work? Each little hole corresponds to a single connection the computer. For our purposes, we will only use Pins 2-9, 10-13, 15 and Now, when it comes to creating any devices, we need to have the following things; An input, an output and ground. An input is a value that is SENT TO the computer to be processed by your program. An output is a value that is SENT TO the device. A ground is used to complete the circuit that is connected to the outputs and inputs of the device. The following pins are used correspondingly: Output: 2-9 (referred to as D0-D7) Input: 10-13, 15 (referred to as I0-I5) Ground: 18-25

4 This is a sample device that can be interfaced with the parallel port

5 Pins and Soldering Wire Pinning: 1) Strip the wire end about 0.5cm using a wire stripper 2) Insert a pin on the end of the wire you just stripped. 3) Now take a nose-plier and squeeze the ends of the pin shut so it doesn t slide off. 4) Yank on the pin a little to make sure it doesn t come off. A loose connection will cause many problems later on. Pin Insertion: 1) Insert the pin halfway into the DB-25 2) On the other end of the DB-25 take a nose-plier and pull the pin out slowly until you hear a small click. Soldering: Soldering is the strengthening of a connection between two joints using an alloy called solder and melting it over the joint using a soldering gun. 1) Strip 1cm off the end of the wire. 2) Take a nose-plier, or use your fingers, and carefully and tightly wrap the wire end onto the component lead you wish to wire (for example, secure the wire around the lead of an LED. 3) Now carefully direct the tip of the soldering gun to the connection joint. Simultaneously touch the soldering wire to the soldering gun tip and the connection at the same time. 4) Once the solder-wire melts onto the connection, move away the soldering gun and let the connection cool. Careful not to heat it up too much or you will discharge and fry the whole mechanism and it will not work anymore.

6 Software The program you will be using to control the device you have created is called: Bloodshed Dev Pascal It is called a compiler and it sends instructions to your device. This is the link to download dev-pascal Install this program. When it opens click on a button called New Source File Now before you actually program anything, you will have to create a new folder. Now go back to Dev-Pascal and -> Ctrl + S to save the source file. Now save this file in new folder you just created. You need to create a new folder for every program you create. Now highlight unit until begin and delete it all until you have begin and end left. It should look like this: What you will also have to do is to copy-paste the port files that will be provided by your teacher and paste them into your folder! (Port.unit, port.pas, etc...)

7 Now to control something simple like what will be required for the LED project, all you will need is output. The code required to basically turn on and off an LED is as follows: uses port, crt; //this program needs port unit and crt library to work var //declaration of variables x: integer; //declaration of X variable as an integer; begin //begins the main program block x:=0; //initializes X to equal 0 repeat //loop procedure begin //begin compound statement writeport(888,1); //turns on D0 delay(500); //hold for 500ms (0.5 seconds) writeport(888,0); //turns off D0 delay(500); end; //end of compound statement until x=1; //it will never equal one, therefore this will go on forever end. //end of main program Now click on a button called Compile and Run. You can find this by clicking on Execute -> Compile and run. This will open a black window and will run the instructions you have programmed in your compiler. If you have error messages, read them and try to comprehend what they mean. Usually they tell you what the error is and what line it is located on. When you understand these basic principles, you will have enough skills to successfully manipulate many other devices such as traffic light systems, music box simulators and any other peripherals that require output.

8 In order for the computer to receive data, you will need commands that process input from sources such as push buttons. This will be covered in Grade 11.