Reading from Parallel Port using Inpout32.dll

Step 1: If you haven't gone through Tutorial #1 and your a novice.  I suggest that you should scroll up.

Step 2: Go to the 'Design Tab' and drag another button to the form window.

Step 3: Next, double click on it and then add the following code in the 'eventhandler' for Button2.

Dim Value2 As String          'String named Value2
Value2 = Inp(&H379S)        'Now Value2 has the values in 'signal port'
MessageBox.Show(Value2)  'A popup will indicate the current value written

Step 4: Run It!!! Press F5 or go to Debug/Start Debugging.

Step 5: Click on Button2 and watch for the popup window.  It should read 120 Decimal.

Explaination

What are Hex, Bin, Dec?

They are representations of numbers at differnt bases.

 

Hex = Hexidecimal Numbers (Base 16)

Bin = Binary Numbers (Base 2)

Dec = Decimal Numbers (Base 10)

 

We are most familar with base 10 since we count in decimal however computers are only familary with base 2; .ie 1's and 0's or 'on' and 'off.'  I'm not going to elaborate more than this.  To change between bases, simply use Microsoft Calculator that is already built in.  Just remember to change it from the 'Standard View' to the 'Scientific View.'  Write in the numbers and then simply click on what base you would like to see the number represent in.

Using the Status Port?

In Tutorial #1; we saw the MessageBox popup window showing a value of 255.  You might ask yourself, why is that.  First of all, DUH! We wrote 255 Decimal or FF Hex to it and ofcourse we can write anything else (0 - FF).

 

In Tutorial #2; we saw the MessageBox popup window showing a value of 120.  Again you might as yourself, why is that.  The answer is not as obvious.  You might think the value should be '0' since we wrote nothing to it & we didn't connect anything to our parallel port yet.  The answer is that Bit 7 (S7) of the signal port is inverted! (Ahhhhh) and S7 - S3 are always high enable.  (Yes!)

 

S7' = 1' = 0

S6 = 1

S5 = 1              

S4 = 1

S3 = 1

S2 = 0

S1 = 0

S0 = 0 

01111000bin = 120dec 

So you might ask yourself, how do we use the status port!!!

 

Just tie any of your status pins (any red pin) to ground (any green pins) and you should see a value change when you run my program again.

You see, on the status line; the pins are 'high' .ie 5V.  To enble them for reading purpose you'll have to ground your status pins. (OOOOOHHH!!!)

 

Examples:

 

Example 1: Nothing Connected to Status Pins

 

The result should be: 120

S7	S6	S5	S4	S3	S2	S1	S0
0	1	1	1	1	0	0	0

 

Example 2: Status Port (S7), pin 11 is grounded

 

The result should be: 248

S7	S6	S5	S4	S3	S2	S1	S0
1	1	1	1	1	0	0	0

Example 3: Status Port (S5), pin 12, is grounded

 

 

The result should be: 88

S7	S6	S5	S4	S3	S2	S1	S0
0	1	0	1	1	0	0	0

Comments & Sourcecode

There you go!  I know this was very long, but I hoped it helps.  If you need the code, I’ll be happy to share.  It’s in VB Express although. 

Download sourcecode

Email me at phebejtsov@yahoo.com for questions.

Regards