Instrument Control (GPIB, Serial, VISA, IVI)

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Basic Serial I/O problems (begineer)

Good afternoon all.

 

I am currently attempting my first Labview Project. We have a pneumatic pressure controller that is to be automated using Labview.

I am currently trying to get some basic comms going with it, but unsuccessfuly.

 

I'm using the eval version of Labview 8.6 (with Augusts Device Drivers).

 

The controller has both GPIB and RS232 comms options, for basic proof of concept I will be using the RS232 link.

 

I have tried using most available ways for communicating from VISA via MAX, VISA via the Basic Serial Read/Write example and my own (poor) attempts at using a new VI with VISA calls.

I can succesfully write data to my controller ( I can switch it between local and remote modes with M<CR> and R0<CR> for local and R1<CR> for remote. The front panel of the controller responds accordingly). But for the life of me cannot get any data out of it.

 

The controller is a GE Druck 520 Pneumatic Pressure Controller. (No LV drivers)

 

The only success I have had with getting data out of it is by setting the controllers mode incorrectly. I have been through the setup options more times than I care to admit at this point.

I can confirm that the basic parameters (Baud Rate, Parity, Stop bits etc) are correct for COM1 and controller, to the point where all write commands are working.

The only way I can any info out of it is by setting the controller mode incorrectly.

 

One of the many setup options is Output Mode. There are 3 options -

 

Direct - Used for one to one applications( Sounds like the correct one to me)

Addressed - For applications where more than 1 controller is connected to the loop. (I am only using this 1 device on COM1).

Printer - Used to continuosly output data to a printer (selectable frequency of output)

 

In direct mode I can write but not receive.

In Addresses mode I have had some very strange and inconsistent results, mostly useless.

In Printer mode I get more data out than I can shake a stick at. But its completely uncontolled.

 

I am using a point to point RS232 cable (Pins 2 to 2, 3 to 3, 5 to 5 with 7 + 8 linked and 4 + 6 + 9 linked) as recommended in the user manual for software controlled handshaking.

I have tried pretty much all combinations in the controller RS232 setup menu. But to be honest at this point I'm fumbling in the dark. I'm fairly sure my cable is good as I have seen bidirectional data)

 

I have trawled the NI website fairly extensively but found nothing to help so far. But I know what a big website it is (used to work for NI).

 

If any of you kind gentlemen can help in any way it would be much  hugely appreciated.

 

Sincerley,

 

Matt.

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Dont worry chaps,

 

It's now playing the game.

 

Looks like a combination of ignorance (90%), Serial port errors (5%) and controller setup (5%).

 

A very relieved,

 

Matt.

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