Can I use labview to send logic hi/lo at Tx of serial?

[seree]

Can anyone suggest me how to use labview to send logic hi or low out at Tx so that I can perform hi/low voltage/current signal measurement? Any help is most appreciated.

[Doug (CapeFl)]

Use the "Write to Digital Line" vi - which sets a digital line to high or low based on how you code it. Its in the Functions > Data Acquisition > Digital I/O palette.
Good luck with it, Doug

[Rob Cole]

There is no way to directly hold the Tx line of the serial high or low. The closest that you can come is to send series of 0xFF's out of the serial port so that you have a set of pulses. If you configure the serial port using "Serial Port Init.vi" to 110 baud, then the pulses are the longest possible.

Of course, you could use some caps to smooth out the signal some, but that could seriously affect your current measurement (if I understand that you're trying to measure the current from the serial port).

Have fun trying it.

Rob

[jwf]

I do not know how you can manipulate trasmit or receive from LabVIEW, but I can tell you how to control some of the other lines on the RS232 port. First you open a VISA session the to COM port in question and then wire that to a property node. Then in the propserty node look under 'modem line settings' and you should see: DTR state and RTS state. You can write to these to control these lines.

[JeanPierre]

You can use "Send Serial Break.vi" that will assert the Tx line for some
input delay in ms.
The function is also available with VISA but you can't set the duration (it
will last 250-500 ms).
The VISA serial break function does not work in LV6 as shipped; you have to
contact NI to get a fixed VI.

Jean-Pierre Drolet
Scientech R&D

"seree" a écrit dans le message news:
506500000008000000A2280000-993342863000@exchange.ni.com...
> Can anyone suggest me how to use labview to send logic hi or low out
> at Tx so that I can perform hi/low voltage/current signal measurement?
> Any help is most appreciated.

[Faraclas]

I am also interested in holding the serial break line for an indeffenite amount of time.  I am using the given serial port so I will need a complete software solution.  It seems that the Serial Break vi is limmited to 500ms. Thanks.

[Wayne.C]

Look at Property: Serial Settings: Modem Line Settings:Break State

This should let you take manual control of break state and hold until property is unasserted.

[Faraclas]

That is correct.  Thanks a bunch.