interfacing a PC

[uranium05r]

hi everyone,

im new here... well i need your help guys. i have this graduation project to finish, i was planning to build an external input device,(like a numpad) that accepts a user password then sends it to the computer, then returns a logic 1 or 0 output to it... Any idea guys what kind of interfacing system i will use!?

thanks!

 

[skulenov]

Hi uranium

You could use simple microcontroller and a RS232 level converter to communicate with PC trough a serial port. you will also need some kind of program on a PC to 'talk' with microcontroller...
you could also just connect keypad to parallel port and read from it trough a PC program...

 

[uranium05r]

thanks skulenov for the reply,

well i asked our higher years, they said that parallel port is more sufficient. have any idea about it... i designed a 12 inputs(from the keypad itself) to the PC and 2 outputs from the PC to the keypad(for the LED on the keypad)...

then another problem was, i think i need to use a multiplexer cause there will me more than 1 keypad placed on different areas and has 1 common PC... Get the idea?...

well me myself is comfused, and didn't know where to start..hehe thanks!

 

[skulenov]

ok, so use a multiplexer... you can wire it in such way that it routes power only to one keypad at a time, one that is first used... you could place a LED on every keypad that would indicate that it is active(has power)...

 

[uranium05r]

thanks, we have the same idea...

may i ask, its my first time to interface a printer port, is there any specific address for the input and output, like the interfacing in the PCI slots?

Would it not bother you if i ask how does this printer port really works?
Any sample circuits, so that it can help me analyze it easier?

thanks skulenov for helping me out...

 

[skulenov]

yes, there are addresses for serial and parallel ports but i dont know them. go and search in google for the terms and also search for the pictures of interfacing printer port... it's really not black magic but it was some years ago that i was doing something with that so i really don't recall it anymore... sorry.
at the time, i was using C for making control programs for printer port...

 

[skulenov]

i think you can get address if you go to device manager, open lpt port go to resources tab and look at the numbers for I/O settings... in this way, i think you can get I/O address of any component in your computer... correct me if i'm wrong!

 

[uranium05r]

what about...

Hey skulenov,

what about using an external keypad like those of a keyboard... it uses USB. Any idea how to use the device, when there are two of them connected and needs only one to function at a time? The same concept like what we discussed earlier?... would it be possible?

Thanks...

 

[sgt-fig]

hi:
sgt fig here. if you want to, you can learn some visal basic and create a windows based program tht doeas this for you. there is a book that will teach you Visual Basic very quick and comes with an limited compiler (compiler-inshort= changes the text to machine language so that your computer can understand it). Although the book is old it is still functionable with windows all the way to XP, and although the Visual Basic tought is Visual Basic 4, it works. here is the info: VISUAL BASIC 4 IN 12 EASY LESSONS, second edition by Greg Perry or you may try newer versions of VB.
Good luck
SGT FIG

 

[bacterozoid]

If you're using the parallel port, you'll need to be sure to unlock it first - I know at least running Windows XP (and anything up from there), there are mechanisms in place that will prevent you from using the parallel port like you wish. Fortunately, there are programs that can fix that for you. Look at using a program called "UserPort". You should be able to get it from here:

EAS: Designs and Ideas

It may also tell you the addresses you want...

You will need to write a small program in Windows to accept and process your input. If you work on a really low level (like assembly), you will certainly need to know the address of the parallel port. I'm not sure how all that works if you're writing in in VB or C, though.