# 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. ## đŸ“Ĩ 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. ## 🕹ī¸ 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. ## 🛠ī¸ 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). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.augelab.com/function-blocks/input-output/communication/serial-write.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.