Modbus Vs. GPIB

I have created a number of drivers for GPIB devices (voltmeters, generators and whatnot) using labview and it has always been pretty simple - just a matter of finding the right table in the instrument's manual and saving the right device-specific code as a string and passing it through a VISA write.
Well, I now have to create a driver for a GS3-2025 Durapulse variable speed drive, but it communicates via Modbus, not GPIB, and I have been having some difficulties.
For starters, I have downloaded nimodbus.mnu and placed it in my user.lib folder, and have the modbus example vis (though they havent done me much good).
I have also tried reading the introduction to Modbus at http://www.ni.com/white-paper/7675/en
However, the introduction has been little help for the same reason the GPIB introductions gave me little help when I was learning to write a GPIB device driver - it is a complete generalized introduction to how the communications system works, even though much of the functions described are handled by the VISA vis automatically - rather than a 'what you need to know to make a driver' type of instruction.
So, specifics:
http://www.automationdirect.com/static/manuals/gs3m/ch5.pdf
The above link is to the manual for the GS3 series of variable speed drives.
I guess my first question is:
In the pdf manual for the GS3, there are 3 columns, Hexadecimal, Modbus decimal, and Octal, and I am not sure which column (if any) represents the actual commands I need to send the device.
Second question: the NI Modbus library vis - do they take the place of the VISA functions, or are they to work WITH the VISA functions?
3rd question: if you scroll past the tables in that GS3 programming manual, (page 5-23) there are some codes listed that don't match up with the tables in the beginning. All of the V20XX codes in that grey bubble dont seem to match anything in the tables, so I am not sure what they are.
The problem with being so new to Modbus - I am not exactly sure what are the right questions to ask, let alone the answers, so if you noticed a fundamental misunderstanding I seem to have about the way Modbus works, feel free to point it out. My main goal is to get a driver for this variable speed drive so I can write a program in LabVIEW to control it, and I am having problems figuring out which codes I need to actually program it, and the syntax to use in LabVIEW.

Thanks for being patient, I have been having some trouble understanding the ModBus language.
I compiled a graphic of the ModBus library .vis in labview, (attached) that shows and labels the inputs.
There is one .vi with "holding registers" that is an output only - this must be the 'read only' you were talking about, but I do not see an "input registers" control.
Maybe I should start a little more general to give you an idea of what it is I am trying to accomplish:
We have a variable speed drive that I want to be able to communicate to. The full manual is available here.
The drive comes with a controller with basic functions that I need to replicate - run/stop/reset, as well as up/down arrows that control the frequency when the parameter P4.00 is set to 1 (which is the default). When the parameter P4.00 is set to 5, the frequency can be controlled by the RS-485 input, which is the goal.
As I said before, the modbus decimal function for P4.00 is 41025, as shown in chapter 5 page 6, which should translate to 024 (as per your previous post, RavensFan).
I am not sure which modbus .vi (shown in attachment) and which inputs to use to set the parameter P4.00 to the value of 5.
Side note: I only brought up the individual GPIB bus inputs as an analogy, it may have been wrong, but it seemed to me like the 'coils' are the individual bit-by-bit inputs for ModBus, just like the individual 'pins' in the GPIB bus.
Attachments:
Modbus labVIEW vis.jpg ‏199 KB

Similar Messages

NI 488.2 software failing Troubleshooting Utility

I am unable to control my instruments using my known good software and a known good GPIB-USB-HS controller. I am using Teststand to call VB6 and VB.NET code which is working on other PCs. I am running Windows 7 and using NI 488.2 version 2.8.
NI MAX identifies the controller and my instruments. I am able to communicate with my instruments through NI MAX. However, the Troubleshooting Utility shows that the software is failing.
The "Help" button provides the following:
Unknown NI-488.2 Software Error
An unknown NI-488.2 software problem has occurred. Try the following to resolve the problem before calling National Instruments:
Restart your system.
Run the NI-488.2 Troubleshooting Utility again.
If you still have the problem, try the following:
Repair the NI-488.2 for Windows software.
Restart your system.
Run the NI-488.2 Troubleshooting Utility again.
Obviously, these steps did not solve the problem.
My software is unable to get a handle to the controller and my function calls do not populate anything in NI-SPY.
I tried installing the latest 488.2 version (3.1.1) which did not help. I tried uninstalling all NI software and then re-installing only the 488.2 software. That did not help either.
Any thoughts?
Solved!
Go to Solution.

I found the solution to this problem.
We are using an ICS Electronics modbus to GPIB converter to talk to a Watlow F4 thermal chamber controller. The ICS module comes with a utility and drivers. We don't need that software but our technician installed it anyway. Part of that install includes a file called "gpib-32.dll". The NI software also uses a file called "gpib-32.dll". Our NI software was failing because it was accessing this library and finding something completely unexpected. I replaced the .dll with one from a working install and that corrected the problem.
Interesting that neither the "Repair" nor "Uninstall/Re-Install" could correct this problem.
By the way, gpib-32.dll is not in C:\Windows\System32 on my Windows7 installs. It is in C:\Windows\SysWOW64\.
Steve

Utility MODBUS RTU Receive Message.vi Error

I am currently using the watlow F4 drivers that i got from NI. One of the private files: Utility MODBUS RTU Receive Message.vi is giving me errors everytime i run anything. I have narrowed it down to the property node giving me this specific error attached below. If i take this property node out, then it will time out on the visa read. I have tried to adjust time outs, and bit sizes as seen in other forums, and still wont help.
I using the ICS Electronics(model 4899A) GPIB to MODBUS interface.
Attachments:
Error.jpg ‏1245 KB
modbusrecieve.jpg ‏1559 KB

what was the outcome of your debugging?
this is my situation:
I am having a timeout error (-1073807339) see attachment . I have stuck 100msec delays before and after the read visa with no change. I am attempting to communicate with an F4 controller with a very simple vi (using NI WATLOW drivers). I am starting a profile, aborting a profile, current step, current temp. I started my project by validating hardware and I used Watview as a sanity check. The communication path is F4D (RS485) / RS485 to RS232 converter /RS232 to USB converter /PXI chassis.
During development the vi worked fine. After saving my project, I shutdown Labview, restarted labview, restarted my vi and then the MODBUS RTU RECIEVE message error (timeout). I did the usual check of comm port with MAX, revalidated hardware with Watview (verified the Watlow read the thermocouple), and still MODBUS RTU RECIEVE message error (timeout).
I have confirmed that there is a combination of opening my project, starting my vi, then starting the NI "CLOSE" vi, restarting my vi, which clears the timeout problem. If I were to close Labview and reopen my vi, problem reappears.
Attachments:
error.doc ‏202 KB

Preciso de um conversor de 4 a 20mA para GPIB. Voces fornecem

Gostaria de saber se vocês fornecem uma solução para medição de sinal de corrente padrão de instrumentação de campo (4 a 20mA) para protocolo IEEE 488 (GPIB). Um cartão de conversão ou algo deste tipo?

Acho que acidentalmente você colocou a sua pergunta no grupo de TestStand, que é um Software utilizado para automação de testes.
Basicamente a linha de produtos da National inclui entre outros produtos, instrumentos/placas para serem acoplados ao seu micro, chassis PXI ou fieldpoint bus.
Para leitura de correntes e tensões, a National Instruments oferece o Digital MultiMeter NI-4060 que é uma placa padrão PCI que quando acoplada ao seu micro pode efetuar leituras de corrente, tensão e resistência.
Na área de GPIB a National Instruments oferece placas GPIB e conversores de bus tipo GPIB-USB, GPIB-Ethernet, etc.
O catalogo online pode ser acessado a patir da página www.ni.com
Além disso, existe um grupo de discussão específico para instrume
ntos GPIB em exchange.ni.com. Em geral as perguntas são feitas em inglês, para que um maior número de usuários tenha acesso as perguntas e respostas.
Roberto Piacentini
Applications Engineer
National Instruments
www.ni.com/support

GPIB Ethernet/100 Performance

Does anyone have some real world peformance measurements on the transfer speeds of the NI GPIB-Ethernet/100 box. I am very disappointed in the performance of a block read which is approximately 6ms/byte transfer (tested from 20 bytes to 32kbytes block transfers). This is on a 100 Mb Ethernet. I can ping the box with 64 byte round trip transfers at ~0.7ms/packet.
I almost feel that the GPIB-Ethernet Box is not buffering my GPIB transfers.
Thanks

Actually ignore my question. My transfer speeds are ~6 microseconds/byte (not milliseconds!). This is still a little slower than I would like, but not totally unreasonable! Note the vertical axis in the included plot (pdf) is in ms, so the linear coefficient in the fit equation is 13 microseconds/(16 bit word).
Attachments:
GPIB_ENET_Plot.pdf ‏25 KB

Lookout modbus plus performance

I'm running 9 Schneider Electric PLCs Compact 265 connected to Lookout v5 PC via modbus plus. I have cyclic stalls of transport, each 50 secs or so, which last for 3 or even more seconds. I've tried all the settings there are on modbus object in Lookout, but with no success, only different graph shapes in performance monitor (you can have a look at graphs at the end of mail). Even single PLC on network (with others shut down) freezes the communication for more then second, which is unacceptable since I need to refresh my data at least each 350ms.
I've considered 3 things:
1. PLC underperforms
I've checked scan time in PLCs, they're all running smooth with scan time under 90ms. This time doesn't increase even during modbus peaks, I've reduced watchdog to 100ms and it never triggered. Looks to me like plc has more than enough time for modbus, so plc should not be the problem.
2. PC underperforms
Hardly a problem, PC running under 5% most of the time, never goes over 50% no matter what I do.
3. modbus underperforms
Statistics show no garbled or timed out frames on any plc, so wiring should be fine.
PLC uses 130 registers of memory (type 4 – holding register). With all registers back to back (no slack between registers), this should mean that all the memory can be transferred in 2 frames. This also means total data load per sec should be
9 plcs * 3 refreshes * 130 reg * 2 bytes = 7030 bytes.
Even with overhead included, this is so little compared to theoretical 120 kbytes modbus plus should be able to perform, so nothing else for me to do but scratch my head.
I've checked Lookout source for any loops which could initiate some read or write at 50sec cycle, but there's nothing even close anywhere in program.
Am I missing something? Can anyone tell me why modbus freezes my system?
Bye everyone,
Darko
SVETLOST TEATAR

Hello,
It’s been a while since I last checked the forum, but in the meanwhile I’ve resolve the problem.
The solution lies in modbus.ini and the way modbus object communicates with modbus secondary, an issue not properly covered by help and ni.com. Unless defined otherwise in modbus.ini, modbus object will refresh all of the configured memory points in your plc each 50 or so polls (I can’t remember which is the default value). This can be a problem if the number of memory points is large, because it congests modbus and creates performance stalls.
You can read more about this here: Lookout Driver Objects - Custom INI File Settings (http://zone.ni.com/devzone/conceptd.nsf/webmain/E54F75254BBE772786256CFC00700B5F).
Thanks everybody for joining in.
Bye,
Darko

Performance of Modbus using DSC Shared Variables

   I'm fairly new at using Modbus with LabVIEW. Out of the roughly dozen tools and API's that can be used, for one project I'm working on I decided to try using Shared Variables aliased to Modbus registers in the project, which is a DSC tool. It seemed like a clever way to go. I've used Shared Variables in the past, though, and am aware of some of the issues surrounding them, especially when the number of them begins to increase. I'll only have about 120 variables, so I don't think it will be too bad, but I'm beginning to be a bit concerned...
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    I'm guessing that:
1) All the caveates of shared variables apply. These really are shared variables, it's only that DSC taught the SV Engine how to go read them. Is that right?
   And I'm wondering:
2) Is there any performance improvement for reading an array of consecutive variables rather than reading each variable individually?
3) Are there any performance issues above what shared variables normally have, when using Modbus specifically? (E.g. how often can you read a few hundred Modbus points from the same device?)
Thanks,
    DaveT
David Thomson Original Code Consulting
www.originalcode.com
National Instruments Alliance Program Member
Certified LabVIEW Architect
There are 10 kinds of people: those who understand binary, and those who don't.
Solved!
Go to Solution.

Anna,
    Thanks so much for the reply. That helps a lot.
    I am still wondering about one thing, though. According to the documentation, the "A" prefix in a Modbus DSC address means that it will return an array of data, whereas something like the F prefix is for a single precision float. When I create a channel, I pick the F300001 option, and the address that is returned is a range: F300001 - F365534. The range would imply that a series of values will be returned, e.g. an array. I always just delete the range and enter a single address. Is that the intention? Does it return the range just so you know the range of allowed addresses?
   OK, I'm actually wondering two things. Is there a reason why the DSC addresses start with 1, e.g. F300001, instead of 0, like F300000? For the old Modbus API from LV7, one of the devices we have that uses that API has a register at 0. How would that be handled in DSC?
Thanks,
    Dave
David Thomson Original Code Consulting
www.originalcode.com
National Instruments Alliance Program Member
Certified LabVIEW Architect
There are 10 kinds of people: those who understand binary, and those who don't.

How to Plot number and string in one row (data logger counter via MODBUS) ?

hi all i made data log quantity using Digital Counter via modbus (RS-485) to monitoring quantity and reject that has and Name Operator, Machine and Part Number.
i have problem about plot the number & string in one row, as shown on the picture below :
how to move that string on one row ? i attach my vi.
Thanks~
Solved!
Go to Solution.
Attachments:
MODBUS LIB Counter.vi ‏39 KB

Hi rhiesnand,
right now you add 2 new rows to your array.
The solution is to concatenate both row parts to one bigger 1D array before adding that array as new row to your 2D array!
Like this:
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

How can i get the count vaule from GPIB?

I want to get the count waule from GPIB ,but I find that the vaule I get from GPIB now is the trace vaule ,
so I ask How can i get it.

The count of what? What kind of instrument are you using?

Getting wrong values from modbus slave

Hi,
I'm trying to get data out of a lumel na5 digital meter. The device is connected via its RS485, through a RS232->RS485 converter to the RS232 port of the PC.
I've donwloaded the NI modbug library, and was able after some work to communicate with the device.
The problem is that the data I get out of it is wrong. I monitored the request and response data that the VI send, and it looks ok but the data is not correct.
Anybody has some similar experience?
Thanks in advance,
Eyal.

Hi,
I do not have any experience with your device but, if you get data (even if it is wrong) from your device with a ModBus protocol you have your communication working !!
The wrong ModBus data is often caused by simply using the wrong register number(s). Start at 0 or 1, hexa and decimal mixup, invalid register numbers in the range, things like that.

I am using the MODBUS library and can't receive data, however I can send it just fine?

Hi,
I am using the Modbus Library to communicate with a VFD to control a fan. I am using the master write and read vi. I can write data to the VFD and get the fan to do what I want. The VFD is supposed to send a confirmation packet after I tell it to do something and I can also read its registers. When I debug the VI it shows the problem is the buffer always reads zero and the VI timesout. If I watch the lights of the USB to RS 485 adapter I am using to interface with the VFD, I see that the RX light flashs right after I send a message. So I should have something in the buffer. Does anyone have any suggestions?
Aaron
Solved!
Go to Solution.

Ok, heres what happened for anyone who has this problem. In the MB Serial Receive.vi The Bytes at Port property node was reading 0 even though there was something in the buffer. The program execution was then stuck in a loop till it timed out and never went on to read anything from the serial port buffer. I didn't spend too much time wondering why that VI didn't work and created my own. With an appropriate delay after writing to the serial port, I used the same Bytes at Port property node and was able to get the right number of bytes to then feed the read VISA vi the number of bytes to read. I got the right response message and everything seemed good. But of course NOT! I then experimented with writing different speeds to the VFD to get the fan to run at different speeds. I found a small range of speeds where I would get no response from the VFD, either by it functioning or sending me a response packet. After quite some time, I found there is an error in the LRC-8 code in the MODBUS NI library. It does not mandate the LRC be a two character value. So if your LRC turns out to be a single character value such as F (which should be 0F) you get an incomplete MODBUS message. This was easily fixed in the LRC8 vi by telling the 'number to hexidecimal string' vi to produce an output with a minimum width of two. Then everything worked great. Moral of the story is the MODBUS library is clunky.

Old visa open, error code 1073807343, using VISA with a GPIB device, and VISA resource names

Hi everyone,
I'm trying to get a SRS model SR720 LCR meter (manual on this page) working with LabView, connecting it to my PC with an Agilent 82357A GPIB/USB interface (manual on this page). I'm running MAX version 14.0, and NI-VISA version 14.0. I'm running LabView version 13.0f2, 32 bit.
I followed the directions on this page, and I'm pretty confident I can communicate with my LCR meter, because I can go to NI MAX->GPIB0::17::INSTR under "devices and interfaces", then go to the VISA test panel, go to the I/O tab, and I can enter a few commands from the SR720 manual, like changing the frequency, and I see the light on the LCR meter change to what I just told it to do. Here is a picture, just to illustrate it:
Also, if I do the *IDN? command, it returns "
9: Write Operation (*IDN?)
Return Count: 5 bytes
10: Read Operation
Return Count: 41 bytes
StanfordResearchSystems,SR720,08087,1.03\n
So, that's good too. I also made the alias of this device "MyLCRmeter", but that shouldn't matter for now.
Now I'm trying to get it to work in a more usable way. The SR7xx drivers that LabView found for me came with a couple sample programs, one called "Getting Started.vi". I tried to just simply see if it worked, changing the "instrument descriptor" field to "GPIB0::17::INSTR", since that's the one that seemed to be the right device in MAX. Here is a picture of the front panel of "Getting Started.vi":
Trying to run it like this gave me this error (code -1073807343):
Old VISA Open in SR715/720 Initialize.vi->SR715/720 Getting Started.vi
Doing a bit of searching on these forums, I found these few threads (1 2 3), which seem to tell me that, since this program was written, the way you open VISA has changed. In the 2nd of those links, one guy said:
You just have to replace the Old VISA Open function with the VISA Open that is on the Instrument I/O>VISA>VISA Advanced palette. When you do that, the wire to the string that was used for the resource name will be broken. Delete the string and make the actual VISA Resource Name visible on the front panel. Wire the VISA Resource Name control to the connector pane where the string control was (upper left connection).
So, I went into the sub-VI Initialize.vi, and did that. Here is a picture of what the front panel and block diagram of the sub-VI Initialize2.vi (I changed the name in case I screwed things up, but I'm pretty sure the new one is the one being called by Getting Started.vi) looked like before I changed anything (you can see the Old VISA Open):
and here it is after replacing that with the regular VISA Open, deleting the instrument descriptor string and replacing it with a VISA resource, and connecting that to the VISA Open:
However, as you can see in the image above, and it seems like someone else had this problem in the 2nd thread linked above, I don't see my device listed in the drop-down menu (even if I refresh), only "LPT1" (I don't even know what that is):
No, I wasnt able to select the visa resource from the pull down menu. somehow it seems disabled or something.
If I just enter the VISA resource name from MAX manually, GPIB0::17::INSTR, and save and try running that, I get the error(code -1073807346):
VISA Open in SR715/720 Initialize2.vi->SR715/720 Getting Started.vi
So I'm not sure where to go from there, or why it's not in the drop down menu to begin with. I'm sorry if I've missed something but I've searched about as far as I can go. If I had to guess, maybe one thing could be that in MAX, under Tools->NI-VISA->VISA Options->My System->Conflict manager, I have both Agilent VISA and NI VISA enabled; I know sometimes problems arise from conflicts between different software fighting over the same hardware. Is this okay, or do I need to change it?
Thank you and please let me know if there is any other code/screenshots I could provide that could help!

Hi, I did indeed enable NiVisaTulip.dll under MAX->Tools->NI-VISA->VISA Options->My system->Passports->List of passports. Sorry, I should have mentioned that explicitly.
By install as primary, do you just mean as it is here, where it is selected as the "Preferred VISA"?
Or somewhere else? I installed NI-VISA first I believe, and then the Agilent one, and during the installation of the Agilent one, I'm pretty sure I made it not the primary. Here's what I have in the Agilent (it's called Keysight now) Connection Expert software:
I also have this under the "Keysight 488 options" tab:
Should that be checked? I don't actually know the role of VISA vs 488 here...
What could I try?
Thank you!

Communication problem with Modbus object in Lookout 3.8

What means the error code 06 besides the following alarm message NO COMMUNICATION RESPONSE FROM MODBUS SECONDARY ? Lookout runtime-express version 3.8 build 7

Greetings,
The alarm message "No Communication response from modbus secondary" means that communication cannot be established between the modbus object and your external device. Verify that you have set up the serial port settings properly and that you have configured the modbus object. Verify that your external device is functioning properly and connected to the PC. If all of these things are ok, you may need to increase the receive gap of the serial port settings and the receive timeout of the modbus object. There is a tutorial on the web which outlines the troubleshooting steps for communication in Lookout.
http://zone.ni.com/devzone/conceptd.nsf/webmain/033CD84BAC7E1E7586256A3300756284?opendocument
I hope this information is helpful. Have a good day!
Patrick R.

Data-acquisition with NI 6036E DAQ card & GPIB using an external trigger

Hi all,
I hope somebody could give me some help with the following and answer some questions:
Simple system description:
Labview 6.1
PCI-GPIB card
6036E DAQ card
In my system, I am using an external analog trigger signal (A) for continuous data-acquisition. Characteristics of the analog trigger signal (A) are: ~40 Hz, signal height +1.48V, triggered by rising edge (the analog trigger signal (A) could be changed to a TTL signal). Each data-acquisition is done within ~1.0 ms after the rising edge of the trigger pulse. The timing of the data-acquisition and analyzing procedure is controlled by execution in a sequence structure placed in a loop.
Now, I connected a power meter to the system, to measure the laser power during the data-acquisition. The power meter has two options to provide the laser power data:
a) via analog signal output (voltage corresponds to laser power in watts)
b) via GPIB (direct output reading of laser power in watts).
Problem:
During a certain point in my data-acquisition sequence structure (defined by a frame), I want to use the next occuring analog trigger signal (A) to acquire 1 value from the power meter.
How do I do this in Labview programming for the following two situations?
a) If I connect the analog output from the power meter to an analog input channel of the 6036E DAQ card. The analog trigger (A) would be connected to a second analog input channel (In case the analog trigger signal (A) is changed to a TTL signal it would be connected to the PFI0/Trig input pin on the DAQ card).
b) If I use the GPIB connection of the power meter. The analog trigger (A) would be connected to a second analog input channel (In case the analog trigger signal (A) is changed to a TTL signal it would be connected to the PFI0/Trig input pin on the DAQ card).
An other possibility would be to trigger the power meter directly, so it outputs constantly power meter values at ~40 Hz. How could I than acquire 1 power meter value (at a certain time im my sequence structure) via analog input at DAQ card or GPIB?
Additional questions:
How do I configure the PFI0/Trig pin on the 6036E DAQ board individually as an INPUT?
How do I use an analog trigger signal (A) as counting signal for a loop, or as an activation signal for a sequence structure which includes GPIB commands?
It would be very nice if somebody could give me some help.
Kind regards,
beam

Hi beam,
I just want to verify that I understand your situation correctly:
An external trigger signal (A) is wired to one of your input channels (e.g. CH0) to trigger data acquisition of a second channel (e.g. CH1). Your power meter is connected to an analog input channel, which you would like to trigger with a certain rising edge at some of your sequence structure.
Problem:
During a certain point in my data-acquisition sequence structure (defined by a frame), I want to use the next occuring analog trigger signal (A) to acquire 1 value from the power meter.
How do I do this in Labview programming for the following two situations?
a) If I connect the analog output from the power meter to an analog input channel of the 6036E DAQ card. The analog trigger (A) would be connected to a second analog input channel (In case the analog trigger signal (A) is changed to a TTL signal it would be connected to the PFI0/Trig input pin on the DAQ card).
If a task has been configured to acquire signal from one analog channel, it's not possible to run a second analog input task or to add a second channel on the fly. You had mentioned that it's possible to read from the instrument through GPIB. Is it possible to perform a software trigger such that at a certain frame of your structure, when the trigger signal A reaches voltage "x", a GPIB command is written to your power meter to query a measurement reading?
Additional questions:
How do I configure the PFI0/Trig pin on the 6036E DAQ board individually as an INPUT?
You do not need to explicitly configure the PFI0 line as an input. If you want to use it as an input such that it acts as an analog trigger, simply wire the trigger signal to this pin. When configuring the trigger in your software, specify PFI0 as the trigger source.
How do I use an analog trigger signal (A) as counting signal for a loop, or as an activation signal for a sequence structure which includes GPIB commands?
You can try using the Limit VI to find out when the trigger signal reaches a certain level, and count how many times this level is reached. Similarly, you can use this as the condition to execute GPIB commands.
Hope this helps,
Lesley

Error when running software on computers w/o GPIB interface card

I'm writing some simple GPIB I/O software using the VISA libraries and I'm getting an error when I run the program on a computer that doesn't have a GPIB card. The error is "The application failed to initialize properly (0xc0000142). Click on OK..." The program runs and works fine on the machine that is hooked up to GPIB devices, but I would like to be able to use my laptop for development. I've installed version 2.3 of NI-488.2, so all the required dll libraries are there.
Thanks in advance,
Jeff

Unless you're using all IVI drivers, there is no built in simulation mode. As long as you make calls to VISA that expect a GPIB board, you'll get errors. Even if you had a gpib board, if you write your code correctly, you would also get errors when the board doesn't find an instrument to write to or read from. The only solution is for you to write your own simulation code. Encapsultate your write/read functions with case statements that skip the driver calls and return simulated data.

Modbus Vs. GPIB

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