06-20-2013 10:56 AM
Just curious, what brand/model of serial/USB adapter are you using?
06-20-2013 12:40 PM
It's a very old adapter, one that had the model # worn off! I just picked a new one up and it allowed me to turn the echo off. Thanks again for the help!
12-08-2014 07:36 AM
Hello, I am new on MODBUS and I am trying to read a temperature value from a slave with the same VI as you.
I just know that :
My slave adress is 202
The temperature is on the registre 0x200E
I use a converter USB/RS485 on port COM12
If I run the VI I have a timeout and nothing is written on "buffer de lecture". Can someone help me ?
12-08-2014 07:47 AM
What is the datatype of your constants that you are building into an array? They should be U8. Because I see a conversion dot on your Byte Array to String function, I'm suspecting you do not have an array of U8's, you probably have a U32. In which case every byte you send is getting converted to 00 00 00 xx where "xx" is the U8 value you are trying to send.
12-08-2014 08:00 AM
You are right, I was in U32. I convert it on U8 but the problem is the same
12-08-2014 08:18 AM
Are you sure about your checksum values? When I build your command string and use the LabVIEW modbus library, it tells me the checksum should be BE73 not 65F8. It looks like you just copied the checksum values from message 13 rather than calculating them yourself.
I highly recommend that you use the NI MODBUS Library for LabVIEW
12-08-2014 08:52 AM
Exactly, I just copied the checksum from message 13. If I put BE73 on checksum it works ! Can you explain me how do you obtain the cheksum value with the LabView modbus library ?
Thank you very much for your help and sorry for my bad english
12-08-2014 09:09 AM
The modbus library has all the subVI's built-in to build the commands for you, including the calculation of the checksum. You just need to install it and drill down through it to see how it works.
12-08-2014 09:09 AM - edited 12-08-2014 09:10 AM
It double posted for some reason.
12-10-2014 04:32 AM
When I try to do exactly the same thing as before with the modbus library I have a Timeout and I read nothing. I do something wrong ? Can you just show me where do you find the checksum value ? IS it the "Exception Code" ?