GPIB on PXI RT general questions

[Blokk]

Hello!

First of all, I am a real beginner in the "world of LV Real-Time". I am in the beginning of a new project where one part of the system consists of a PXI system with RT OS including a GPIB interface. This interface will be connected to several Keithley picoamp meters (model 6485 & 6487). The RT code must read data from the Keithley devices, and also perform some commands on the devices (like zero them, turn on/off high voltage, etc.). The other part of the PXI RT application will have a TCP/IP connection to a Siemens S7 system, and send data there plus recieve incoming commands to be executed on the Keithleys. Anyway, interfacing the Siemens via TCP/IP is another nice challenge, and might be a topic of another future post. Right now I just wanna deal with the GPIB part...

I would like to ask people familiar with PXI RT (and possibly with GPIB on these platforms) for best practice & advices:

1. I have got the official driver from Textronix for LabVIEW ( http://www.tek.com/specialty-instruments/6485-software/models-6485-6487-and-6514-ivi-visa-based-driv... ), but the driver operates via a DLL. I think this is not a good idea (is it even possible?) to use a DLL on a RT OS, and adds more complexity (we will have many PXI systems later). Therefore we should implement our own driver using basic VISA functions, am I right?
2. I would like to have a robust RT system, so it should automatically detect all connected Keithley devices, and check also model type (only the model 6487 has voltage supply option). I guess if VISA Runtime is installed on the RT OS, then I can also use the "VISA Find Resource.vi" to get a list of the available GPIB devices? I will also need to program a feature to handle scenario when a Keithley module is turned off or removed from the chain, so the RT OS should not crash, but this should not be a problem...

Any advice and suggestions are welcomed,

thanks!

[crossrulz · Accepted solution]

1.  DLLs are compibled for Windows.  So that will not work on the RT OS, whether it is Pharlap, VxWorks, or RT Linux.  You will need to make your own driver using VISA calls.

2.  Since you have to handle different Keithley instruments, I highly recommend going with an OOP approach.  Most of the similar instruments should have the same commands, so I doubt you will have a deep hierarchy.

My advice right now is to do all of your driver creation and testing on a Windows machine.  All of the code your develop should work just find when you take it to an RT system.  It is the command structure that matters more than anything.