Re: Parallel port and Visual Basic?

Zucker wrote: 
I am in the process of building a circuit that will monitor the start and
finish times for pine box derby cars. I would like to be able to catch these
events by feeding signals, through the parallel port, to a Visual Basic
program. I was thinking of using the eight data pins from the parallel port
to monitor eight lanes.

The electronics are good to go. My problem is with Visual Basic.

Does anyone know how to access and capture bit patterns from the parallel
port using Visual Basic?

Steve

PS...I have asked this same question in several programming newsgroups, but
I have not recieved any responses.



You have several problems.
The operating system may prohibit you from accessing the parallel port.
You may need a driver to enable this.
Visual Basic prohibits you access to the parallel port.
You may need a dll/driver/ocx etc to gain access.
You need some way to time the event.

Variable program latencies.

All these layers of software mean that you can't get an accurate or even
repeatable time measurement.  The newer the OS, the greater the uncertainty.

Suggestion 1:
Do the sense/calculate in a microcontroller and send the answer to VB via RS232 port.

Suggestion 2:
Ditch VB. Run pure DOS. Use the hardware timer in the 8253 emulation...it's the timer that normally runs the beeper.
Program it in something compiled and determinate like assembler or C.
This should give you guraranteed sub-second repeatability.

mike

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