Serial port communication problems

[Giant_Spiders]

Hello.  I am trying to control a MKS Instruments 651C Pressure Controller via RS-232.  Right now, I am just trying to establish basic communication with the device over the serial port.  I can connect to the device with windows hyperterminal using the following settings:

Bits per second: 9600

Data bits: 8

Parity: None

Stop bits: 1

Flow control: None

Once I connect, I go to File-->Properties, Settings tab,and click on ASCII Settings button.  I must check the following boxes (not checked by default) for any communication to occur:

Send line ends with line feeds

Echo typed characters locally

Append line feeds to incoming line ends

Force incoming data to 7-bit ASCII

Once I have all that set, I can communicate with my device via hyperterminal.  What I would like to do now is to use LabVIEW to control the device, so I need to be able to send/receive data over the RS-232 connection via LabVIEW.  I have been using the Basic Serial Write and Read vi, but I am not getting any response from my device.  Looking at the block diagram for the basic read/write, I saw that  Enable Termination Char was hardwired to false, so I changed it to a control and set it to true.  I also changed Termination Char to a control and set it to 0xD for CR.  I still cannot get a response from the device.

I'm guessing that I am still not setting everything for the serial port setup correctly.  Can anyone give me some suggestions on what else to modify to match my hyperterminal settings?  Thanks!

[aeastet]

A line feed is 0xA not 0xD. I do not think you can use a CR you have to use a line feed. That would be the first thing I see.

[Redstrat]

Please attach your code.  I would be guessing at this point without seeing the block diagram.

[Giant_Spiders]

I have tried both 0xD and 0xA and neither seems to work.  According to the manual for my device, all messages must us a carriage reurn-line feed as the end-of-line delimiter, which is why I used 0xD.

[Giant_Spiders]

Here is the code.  It is literally the Basic Serial Write and Read vi with the two changes I mentioned above.

[aeastet]

I have an easy question is it set up to the correct com port?

[Giant_Spiders]

I believe it is.  I can communicate via COM1 through hyperterminal.  I am using NI-VISA, so I select COM1 in my vi as well.  I also have a separate USB serial port that is COM4.  When I switch the cabling and connect to COM4 through hyperterminal it works.  Selecting COM4 in my vi does not.

[Mark_Yedinak]

Have you tried running NI-Spy to see what is actually happening on the serial port? This may help you narrow down what is happening. I also wonder if you are having an issue since you are using 8-bit ASCII when you open the port but in hyperterminal you are telling it to use 7-bit ASCII to read the data.

[aeastet]

I found this LLB from MKS. I realize that it is not the same model but maybe you can see what is going on with what they did.

[Giant_Spiders]

Mark,

I realize this 7-bit ASCII thing may be the problem, but that is the only way hyperterminal will communicate with the device.  How can I get LabVIEW to do this?