Modbus Write

This function block sends values to a Modbus server using a provided Modbus client. Use it to write coils or holding registers from your scenario graph.

📥 Inputs

Enable This boolean input controls whether writing is performed. If not provided or False, the block will not attempt to write.

Modbus Client This input expects a client object produced by the Modbus Connect block. Provide a valid client to enable communication.

Data Generic data to write. Accepts a single value or a list (for writing multiple coils/registers).

📤 Outputs

This function block produces no outputs.

🕹️ Controls

Address Enter the Modbus register/coils address to write to. Use integer values that match your device map.

Data Type Choose between Coil and Holding Register to select which Modbus resource type will be written.

🎯 Features

• Supports writing single values or lists to multiple addresses when the device supports it.

• Lets you choose the target resource type with a simple dropdown: Coil or Holding Register.

• Respects the Enable input so writing can be controlled from logic or user inputs.

• Reports errors to the log if writing fails so you can diagnose connection or configuration problems.

⚙️ Running mechanism

When the block runs:

• If the Enable input is False or missing, no write is attempted.

• If no client is provided at Modbus Client, the block will not perform any write.

• When enabled with a valid client, the block sends the supplied Data to the address entered in Address using the selected Data Type.

• Errors (connection problems, invalid address, unsupported data) are reported to the log so you can act accordingly.

📝 Usage instructions

• Add a Modbus Connect block and connect its Modbus Client output to this block's Modbus Client input.

• Set Address to the register or coil address you want to write.

• Select Data Type as Coil for boolean/coils or Holding Register for numeric registers.

• Feed your data into the Data input (single value or list).

• Use a Logic Input or other control to toggle Enable when you want the write to occur.

💡 Tips and Tricks

• Use Modbus Connect to produce a reliable client and confirm the connection with Modbus Read before trying to write.

• Drive the Enable input from a Logic Input or a conditional block (for example Equals / Greater) so writes occur only under desired conditions.

• Prepare write values using Number Input or by assembling data with blocks like String Merge or Data Write Global / Data Write Local when you need to stage values.

• If you need to save or export values you write, combine this block with CSV Export or REST API - Post to keep external logs or send notifications.

🛠️ Troubleshooting

• No write happening: check that the Enable input is True and that a valid Modbus Client is connected.

• Invalid address errors: ensure Address is an integer within the device address map and matches the chosen Data Type.

• Unexpected data format: for Coil use boolean or list of booleans; for Holding Register use numbers or a list of numbers.

• Write failures: verify connectivity with Modbus Read and confirm the server accepts writes to the target address. Check log messages for details.