Modbus TCP String to EBO AS-P

[kalatech]

Hello,

I have a device connected to AS-P using Modbus TCP. I need to read the serial number and some other values which are string type in the device.

In the Modbus Point menu when I try to add a new value I get Digital, Analog, Multibit and Multistate types, no String. If I create an internal String value, I don't know how to connect it to the Modbus TCP device.

Please advice how to proceed. I was thinking about converting each character in ASCII code and sending it as INT but I can't do it in the Modbus TCP device, so it is not an option.

[CraigEl]

@kalatech modbus transfers data values in bits and bytes and does not have a concept of strings, and there is not a String object for Modbus in EBO.

As Strings are just byte arrays if the customer can read the raw data into a Modbus point it could possibly be input to a Script program and converted. However modbus registers can only be up to 64-bits in length. This is basically an 8 ASCII character string and to go past that you would need to implement a Modbus Batch Read Function to read a batch of strings to ensure they are grouped together. If you encounter polling/error problems etc you may run into trouble.

[kalatech]

I tried to read using 64 bit number but it turned out regarding this string value the device only answers to a modbus request for 10 registers and throws exception for any bigger or smaller amount. Can you give me an example how to use Modbus batch read?

[CraigEl · Accepted solution]

@kalatech refer to the Modbus Registers and Group Polling topic in EBO Webhelp