NI4882 Device Write Issue. Have to double write or I get a timeout.

[johndcollins]

Hi,

I'm trying to interface with a HP 3497A Option 110.

This is my code:

            try
            {
                _dev = new Device(boardIndex, 9);
                _dev.Clear();
                _dev.Reset();
                _dev.Write(ReplaceCommonEscapeSequences("DR3"));
                _dev.Write(ReplaceCommonEscapeSequences("DL3"));
                string resp = InsertCommonEscapeSequences(_dev.ReadString());
                _dev.GoToLocal();
            }
            catch (NationalInstruments.NI4882.GpibException ex)
            {
            }

Highlighted in red is my issue. In order for me to read the response from the device, I have to call _dev.Write(ReplaceCommonEscapeSequences("DR3")) twice or I get a read timeout error.

If I call it only once, I get a timeout error, but calling it twice works.

Can anyone explain this?

This happens for other options as well.

Thanks!

[nyc_(is_out_of_here)]

Before going to all of the trouble of writing code, I would have verified communication first using NI-488.2 Interactive Control available through NI-MAX.

[johndcollins]

Thanks for your reply, but I'm not sure what that would do for me. I appreciate the effort though.

Communication works fine. I can read the values from the device, but I'm trying to understand if I'm missing something conceptionally in code since I have to make the above call twice in order to read the value.

Is there an additional command I have to send?

There is not many code example out there using .NET and communicating with older devices. These devices do not respond to *IDN? etc.

The device does show up in NI MAX as GPIB0::9::INSTR

The above code was supposed to be:

           try
            {
                _dev = new Device(boardIndex, 9);
                _dev.Clear();
                _dev.Reset();
                _dev.Write(ReplaceCommonEscapeSequences("DL3"));
                _dev.Write(ReplaceCommonEscapeSequences("DL3"));
                string resp = InsertCommonEscapeSequences(_dev.ReadString());
                _dev.GoToLocal();
            }
            catch (NationalInstruments.NI4882.GpibException ex)
            {
            }

Thanks.

[nyc_(is_out_of_here)]

---

@johndcollins wrote:

Thanks for your reply, but I'm not sure what that would do for me. I appreciate the effort though.

Communication works fine. I can read the values from the device, but I'm trying to understand if I'm missing something conceptionally in code since I have to make the above call twice in order to read the value.

Is there an additional command I have to send?

There is not many code example out there using .NET and communicating with older devices. These devices do not respond to *IDN? etc.

The device does show up in NI MAX as GPIB0::9::INSTR

The above code was supposed to be:

           try
            {
                _dev = new Device(boardIndex, 9);
                _dev.Clear();
                _dev.Reset();
                _dev.Write(ReplaceCommonEscapeSequences("DL3"));
                _dev.Write(ReplaceCommonEscapeSequences("DL3"));
                string resp = InsertCommonEscapeSequences(_dev.ReadString());
                _dev.GoToLocal();
            }
            catch (NationalInstruments.NI4882.GpibException ex)
            {
            }

Thanks.

---

No. Your communication does not work out fine, or you wouldn't have the problem you are having.

[johndcollins]

Ok, thank you for pointing that out.

Can you try and specifiy what I'm supposed to look for in NI MAX?

It looks like it finds the HP 3497A ok.

I have tried this on another setup with similar results.

[nyc_(is_out_of_here)]

As I wrote above  

I would have verified communication first using NI-488.2 Interactive Control available through NI-MAX.

[johndcollins]

Sorry, I guess I'm not getting what you mean with "I would verifiy communication first..."

I am communicating with the device. It's responding when I send commands. How do I verify communication.

I've run the NI-488.2 Communicator and it behaves the same way.

I have to send the DL3 command twice or the read will time out...Is that the verification you were looking for?

Here is the I/O Trace for the code above:

Here is the Trace if I don't send the second write command:

[nyc_(is_out_of_here)]

Are you sure that the command does not require a CR or a CRLF ?

Do you have access to the manual?

Perhaps you need to add a delay before a read.

[johndcollins]

Thanks for your help..

It was a special eos character that did it.

[KLP]

John,

        What was the special EOS character that you added? I am having the same issue. I have a system in the field that is working properly but the inhouse system is having the double write issue. I have tried adding every applicable character to the end of my write commands with no luck.