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RS232 to GPIB converter using NAT9914
mirna
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10-18-2005 06:31 AM
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Hi,
I'm a student at the Faculty of Electrical Engineering and computing in Zagreb, Croatia.For my bachelor degree im designing a sort of converter.It would be an RS232 to GPIB converter.I'm using microcontroller from 8051 family and NAT9914 as interface to GPIB bus.
The NAT9914 handles the communication layer, but doesn't interpret too much of the data, so if I would like to make IEEE 488.2 compatibile device (which takes care of the required IEEE 488.2 commands ) I'd have to create a software construct for it.
I was wondering if anyone did that.If someone did, I would appreciate to contact me on my e-mail: mirna_1998@yahoo.com or mirna.bartulovic@fer.hr.
I know that there is an NI product named GPIB-232CV-A RS-232 to GPIB Converter, but the whole purpose pf my work is to learn to do it this way if it is possible.
Thanks!
Mirna
Collin M
NI Employee (retired)
10-18-2005 06:15 PM
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Mirna,
I need to clarify your question. You want to create a device with two ports. The first port is GPIB and the second port is RS232. You want to connect the GPIB port to a host computer and connect the RS232 port to an instrument. The device translates the GPIB protocol from the host to the RS232 protocol to the instrument. Is this correct?
If this is correct then the device you are designing doesn't need to do anything special with IEEE 488.2 commands. For example, if you send the IEEE 488.2 command "*IDN?", the response from the instrument to the host depends exclusively on the instrument. Ideally the device you are designing will appear transparent to the host and the instrument. The role of your device is just to translate between GPIB and RS232, not interpret the data.
I need to clarify your question. You want to create a device with two ports. The first port is GPIB and the second port is RS232. You want to connect the GPIB port to a host computer and connect the RS232 port to an instrument. The device translates the GPIB protocol from the host to the RS232 protocol to the instrument. Is this correct?
If this is correct then the device you are designing doesn't need to do anything special with IEEE 488.2 commands. For example, if you send the IEEE 488.2 command "*IDN?", the response from the instrument to the host depends exclusively on the instrument. Ideally the device you are designing will appear transparent to the host and the instrument. The role of your device is just to translate between GPIB and RS232, not interpret the data.
10-19-2005 05:24 AM
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Hi,
Actually, RS232 would be connected to host computer, and the GPIB port is connected to the instrument.The purpose of the whole device (convertor) would be to manage programmable source with microcontroller.
On National Instruments web-site, there is an document about it: http://zone.ni.com/devzone/conceptd.nsf/webmain/40D4BB8DCD8CEB35862568040069E228/$File/AN110.pdf
The thing is that that is an example of 488.1 compliant.With expanded parsing routine it would become 488.2 compliant.
So I was wandering if anyone tried to write software for it, and if someone did would it be a problem to send it to me.
Tnx
Mirna
Collin M
NI Employee (retired)
10-19-2005 09:10 AM
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Mirna, I understand the function of your device now. I still don't see
why you need to parse IEEE 488.2 commands in your device. It is
typically the responsibility of the instrument firmware to do that. For
example, if you send the command *IDN? from the host to the instrument,
the GPIB/232 translator should not alter that message in any way.
Anyone else please comment if I am not correct on this.
Anyone else please comment if I am not correct on this.
Dennis_Knutson
Knight of NI
10-19-2005 09:38 AM
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I agree that the command processing is always done by the instrument itself unless of course the existing instrument doesn't do any
processing (maybe it's register based) and it can't be modified. Placing the converter inside the instrument would then give the user the ability to read/write SCPI-like commands. If the converter is designed to be a general purpose converter for any GPIB instrument, he's taking the wrong approach.
10-21-2005 08:05 AM
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The converter I'm trying to designe is a general purpose converter for any GPIB instrument.
Dennis_Knutson
Knight of NI
10-21-2005 08:24 AM
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Then there should be no interpreting of the commands. Commands such as *IDN?, *RST, are interpreted by the instrument itself. Where these the commands you were thinking of?
