Parallel Port and VB part II

Apr 22, 2005 3 Replies
Z

First, I would like to thank everyone who helped me with my initial post. Using your suggestions, I decided to use a third party dll (inpout32.dll) to access the parallel port using VB6.



My next question is...if I'm only interested in using the eight data pins of the parallel port, what do I do with the status and control pins? Do I tie them to Vcc or Ground? Can I leave them floating?



This website

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states that the port must be set to bidirectional mode before the data pins can be read into a VB application. At the bottom of the page it states "To enable Biirectional data transfer just set the "Bidirectional" bit (bit 5) in control register. This is done by writing 32 to control register." Writing 32 to the control register is done with VB code. I'm worried that any external hookup to the control pins would conflict with the VB code.



Thanks again for your help. Steve


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R

Then, don't connect anything to it on the outside. Leaving them open should be fine, unless you want to use them for handshaking.

Good Luck! Rich

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M

float 'em.

This is a problem with bidirectional parallel port. I always use series resistors with value high enough to limit the fault current to a safe value. Often there's a conflict between desired output drive current and protection. And we haven't even talked about static protection. You always want to use a plug-in parallel port card. Remember that on a motherboard, the parallel port circuitry is in a chip with a LOT of other stuff. Smoking the port can render your motherboard DEAD!! Ask me how I know ;-( mike

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T

Steve,

I use Inpout32.dll with Visual Basic myself. I use the 5 status bits for input and the 8 Data Bits for output. I would not expect any problem from setting C5 high:

Out base_address +2, 32

And I would leave the unused pins floating for sake of simplicity. If you leave them alone they would have value 1 and if you connect them to ground they will have value 0, which is irrelevant since you are not using them.

I have limited experience beyond that. So far I have written a small VB program to test the paralle port test circuit on

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and another to drive an A/D interface via parallel port.

Good luck

Luca

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