How to make in/out Port vis work with COM interface under different windows versions?

[Garfield]

Hello!

I know that the accessHW is necessary for it, so I downlaoded the
this file from the homepage of NI, but there are always some problems
with it.

My program should get the the voltage impulse between
the pins DTR and RTS of a COM interface. After
I installed accessHW under winNT, the voltage between them changed
automatically from 0 mV to about 24 mV , and program
worked well . But this way does not work under Win98 and Win2000,
and this voltage is always 0 so that the device can not make any voltage
impulse.

Could someone give me a software solution for it? Thanks!


P.S:The version of the labview I use is 6.1.

Le

[Dennis_Knutson]

Instead of Inport/Outport, you can set or read these lines with a VISA property node. Select Properties>Modem Line Settings.

[Garfield]

"Dennis Knutson" wrote in message
news:50650000000500000057FE0000-1042324653000@exchange.ni.com...
> Instead of Inport/Outport, you can set or read these lines with a VISA
> property node. Select Properties>Modem Line Settings.

Thank for your answers.

But at first I need a voltage(about 24 mV) between DTR and RTS , it is
the power source of my device.

And there is no problem under WinNT. I don't know what exactly happend,
but there was a 24 mV voltage between them just aftere I installed accessHW,
it is independent of my program, and with close and unclose the switch of
cable
between DTR and RTS I got the voltage impulses that can be counted by my
program.( I measured the 24 mV voltage with multimeter, and if I don't
intalled
accessHW, the vo
ltage would be 0).

But there would be not any impulse at all ,if there is no voltage, this is
the
problem which I met under other windows systems.



Le

[Dennis_Knutson]

You shouldn't depend on a voltage difference between the tow pins unless you need something like 24 volts and not 24 millvolts. All of the signal lines are referenced to ground and the signal lines usually swing between -3 to -12 and +3 to +12 volts. If you truly saw a 24 millivolt difference between two signal leads, then all that means is that they are both at the same logic state. A difference of 24 millivolts is not much and has to do with the UART in your computer and not accessHW I believe though maybe what happened is that the difference is 24mv when both are logic "1" and less when logic "0" or vice versa. If your device requires power from the serial port, then what you'll have to do is control the signal lines in your program and I
would recomend VISA to do that instead of inport/outport. And check the voltage requirements of your device. If this is a device you designed, it should be designed for the lower voltages on new pc's and laptops. In other words, I would depend on 3 volt signals instead of 12. There are numerous references to either RS-232 or EIA-232 on the web. I think a review of the electrical specifications is needed.