Serial communication problem - Modbus ASCII

[StefanieWernet]

Hey,

I try to communicate with a temperature control via VISA. I have problems to understand the received message. The answer to my input string (:070310000001) was :0783096D. I thought 83 stands for the "Function Code" and 09 for the "Exception Code", but I can not find what exactly is the meaning of this.

The process value should normally be something about 21°C (room temperature).

Thanks for help!

[RavensFan]

There are modbus libraries available to use so that you don't have to code your own.

MODBUS Library for LabVIEW

[drjdpowell]

Also this one, which is newer.

[StefanieWernet]

Thanks for your fast answer!

I want to use the VISA ressources in Labview. Is it possible to combine them?

[RavensFan]

Yes.  Those Modbus libraries use the VISA resources.

[StefanieWernet]

I tried the example: MB_Master Simple Serial. I made all approaches, but there still comes a error message: 1073807339.

Shouldn´t it work with this example?

I am a total beginner with Labview and Modbus, so I am happy about every help!

[crossrulz]

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@StefanieWernet wrote:

I tried the example: MB_Master Simple Serial. I made all approaches, but there still comes a error message: 1073807339.

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-1073807339 is a timeout error.  Perhaps your instrument is not setup to talk over the serial bus?

[StefanieWernet]

The instrument communicated via a different program with me, so in my opinion there should be no problem.

I have the correct VISA Ressource and Slave ID. Where else can be the problem?

[RavensFan]

Don't know.  Post some code so we can see what you did.

Perhaps your serial settings are wrong.  Maybe your slave address is wrong even though you think it is correct.

[StefanieWernet]

Going back to my starting problem with the modbus code:

I think it is a Modbus exception code with 09. In all the lists of exceptions codes (e.g.: http://www.simplymodbus.ca/exceptions.htm), there is always 01 till 08 and then 0A (10), but no 09.

Can someone explain this to me?