Yes, Vision Builder AI can actually only be used as a Modbus slave for now (users can implement the master functionality using a Run LabVIEW step).
To configure Vision Builder AI as a Modbus Slave device, select Tools>>Communication Device Manager.
Click New Device, to create the Modbus Master Device you want Vision Builder AI to communicate with.
Give it a name, then select either the Modbus Serial or Modbus TCP as the communication protocol depending on the physical layer used to connect to your device. For serial, you will need to specify the port and Modbus Mode (the most widely implemented is RTU).
Click OK.
Click the Start Server button, next to the Modbus Server, to start the background task that will listen for incoming Modbus messages. Note that the Modbus registers will be updated asynchronously from your inspection, whenever a Modbus frame is received.
The Vision Builder AI Modbus Slave Address is only used to identify the device, when the protocol is Serial, and you use the RS-485 protocol to connect together more than 2 Modbus devices in a multi-device configuration. Ignore this control if you are using Modbus TCP.
We know this dialog is a little confusing and are working towards improving it in future releases.
Once the server is running, use the Modbus Slave step to read and write the Modbus registers (that are located on the machine running VBAI, since you configured VBAI as a slave device).
Make sure that you specify the correct address in your Modbus Master device configuration software for the register you want to access in Vision Builder AI. In most Modbus device configuration software, you must enter a name for the register you want to use. Per Modbus convention, the register address of the slave device is calculated by subtracting 1 from the register name that you specify in the master device configuration software. Vision Builder AI expects register addresses, not register names, so you may have to subtract 1 from the address you defined in the Modbus device configuration software. For example, a register name defined as 2 in your Modbus configuration device translates to register address 1 in the Vision Builder AI Holding Registers table.
| Modbus Device |
Holding Register Name = 2 |
| Vision Builder AI |
Holding Register Address = 1 |
The Modbus data model is based on a series of four tables: Discrete Inputs, Coils, Input Registers, and Holding Registers. These tables do not overlap in Vision Builder AI. Some Modbus devices use the following start addresses for these tables.
- 0x00000 for the Coils
- 0x10000 for the Discrete Inputs
- 0x30000 for the Input Registers
- 0x40000 for the Holding Registers
Because the tables do not overlap in Vision Builder AI, ignore the first digit of the start addresses when entering the addresses in Vision Builder AI. For example, a register name defined as 0x40000 in a Modbus configuration device translates to register address 0 in the Vision Builder AI Holding Registers table.
| Modbus Device |
Holding Register Name = 0x40000 |
| Vision Builder AI |
Holding Register Address = 0 |
Sometimes you need to subtract 1 from the register name that you specify in the master device configuration software and ignore the first digit of the start address to ensure proper register addressing. For example, a register name defined as 0x40008 in a Modbus configuration device translates to register address 7 in the Vision Builder AI Holding Registers table.
| Modbus Device |
Holding Register Name = 0x40008 |
| Vision Builder AI |
Holding Register Address = 7 |
The Modbus Local Registers Terminal accessible from the Tools menu is a useful tool to figure out where you're writing data.
Hope this will help you configure the communication between VBAI and your device easily.
Best regards,
-Christophe
