Serial Write

This function block sends raw data over a selected serial connection. It is built for simple, non-blocking transmissions and provides convenient UI options to convert common data types, append line endings, and control re-transmission behavior.

📥 Inputs

Enable Use to enable or disable sending. When false the block does not send data.

Data The payload to send. Accepts numbers, text, lists, booleans or byte-like values depending on selected controls.

ConnId Identifier of the serial connection to use. Provide the connection id produced by a connection manager block.

📤 Outputs

This function block does not produce outputs.

🕹️ Controls

Data Type Choose how the provided Data will be converted before sending. Common choices include string, integer, float, boolean, and byte/hex formats.

Line ending Select a trailing sequence to append to the payload. Options typically include LF, CRLF, CR or none.

Send policy Choose when to transmit:

• On change only sends when the final byte payload differs from the last sent payload.

• Always sends every time the block is evaluated and enabled.

🎨 Features

• Data type conversion for common formats, so you can input human-friendly values and the block will send the corresponding byte sequence.

• Optional configurable line ending to match remote device expectations.

• Send policy to avoid repeating identical messages when not needed.

• Non-blocking write behavior so the flow keeps running while data is transmitted.

• Works with external connection manager blocks that provide ConnId values.

📊 Running mechanism

When the block is evaluated:

1. If the Enable input is inactive or empty, nothing is sent.

2. If valid Data and ConnId are present, the block converts Data according to the selected Data Type and appends the chosen Line ending.

3. If Send policy is On change, the block compares the prepared payload to the previous payload and skips sending if identical.

4. The prepared byte payload is sent to the serial connection referenced by ConnId without blocking the rest of the system.

📝 Usage instructions

1. Create or select a serial connection and note its connection id.

2. Provide that id to the ConnId input.

3. Feed the value you want to send into the Data input.

4. Set the Data Type control to match your data (for example use HexBytes for hex strings or Bytes for raw byte lists).

5. Choose the desired Line ending if the receiving device expects one.

6. Use Send policy to avoid unnecessary repeats when streaming constant values.

7. Toggle Enable to start or stop sending.

💡 Tips and Tricks

• Combine with Serial Connect / connection manager blocks (the system's connection manager) to obtain and manage ConnId values.

• Use String Input or Number Input blocks to prepare and validate the Data before sending.

• Pre-format complex payloads with String Merge or Data to JSON when you need structured strings (for example JSON messages).

• If you need to log or export sent data, add CSV Export or Image Logger (for visual logs) downstream in your flow.

• For conditional sending based on logic, combine with Logic Input, And, Or, or Greater blocks to gate transmissions.

• For protocol bridges, pair with MQTT Publish or REST API - Post to forward serial data to network services.

• Use Debug Input to inspect the outgoing payloads during development.

🛠️ Troubleshooting

• Nothing is sent: verify Enable is active, Data is not empty, and ConnId references an active connection.

• Receiving device ignores messages: check the chosen Line ending and try different options (LF, CRLF, CR or none).

• Identical messages not sent when expected: confirm Send policy is set to Always if you need repeated sends.

• Unexpected bytes on the wire: ensure Data Type matches the value format you provide (for example use HexBytes for hex strings or Bytes for numeric lists).