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TTL signal via RS 232 RTS

Hi,

I'm new to LabView. I went through some of the basic tutorials so far, but my knowledge is very basic. My project mainly consists of combining linear actuators with a second unit. I've got a vi for the actuators. For the second unit I have to send a gate signal (TTL 0V...5V, various signal length, 1 ms....5s). To accomplish this I'm using a RS232 to TTL converter. I'm using the RS232  RTS pin. The "troubleshoot serial line monitor.vi" let's me switch the TTL ouput manually between 0V and 5V, so the hardware works fine.

My Question:
1. When the RS232 input is low, the TTL output is high (5V). This is how the converter works. So I need to switch the  RTS (RS 232) input to high as an initialization step in my program, since I need the TTL output on low most of the time, accept for the gate signal. Whats the most elegant way to do this?

2. How do I trigger the  RTS (RS232) (send the gate signal). Set the  RTS to low for various signal length (1 ms....5s). Timing is here very important and I might want to go below 1ms, so I don"t want to use a simple wait command.

Thanks....

Thorsten

Message Edited by ThorstenFischer on 02-09-2007 11:20 AM

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Controlling the RTS is pretty simple. You can do it with a VISA property node. Select Properties>Serial Settings>Modem Line Settings>Line RTS State. Change to property to write. Valid inputs for the property are Asserted, Unasserted, and Unknown. The input is an enum and you simply have to right click on the property and select Create>Constant.

The big problem you are going to have is timing. If you are working on windows, timing is not even close to being deterministic and getting accurate and repeatable pulses is not possible with software timing. You should look at using something hardware timed. Some of the NI DAQ boards have a counter output that you can use.

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