Serial lines
The Modbus RTU line node: the physical tuple every unit on the bus shares, its timing, its states, the unit scan, the devices filed under it, and what is locked while the line is enabled.
A serial line is one physical Modbus RTU bus: a COM port with its baud rate, byte format and response timeout, shared by every device wired to it. Lines exist only under the Modbus RTU driver, between the driver and its devices, so the tree reads Modbus RTU > Line > Device > Tag. The page is visible with View connector; every field and verb on it needs Configure connector.
Creating a line
Three gestures create one: Add line on the Serial lines table of the Modbus RTU driver's page, Add serial line (Modbus RTU) in the column's New… menu, and the same entry on the driver's right-click menu. The new line is named "New line" (then "New line 2"), takes the first serial port Windows reports that no other line uses (or COM1, COM2 and so on when none is free), starts with 9600 baud, 8E1, a 1000 ms response timeout and a 0 ms transaction interval, and is created disabled so you can set the physical tuple before the port opens. The feed says so: "Added disabled line 'New line'. Configure its physical settings, then enable it."
The header
The name, the health dot, the state word and the physical tuple on one line ("COM3 · 9600 · 8E1 · 1000 ms") and, when the port failed, the diagnostic text in red under it. The state words are Off, Idle, Connecting…, Online and Port failure; what each means is on Enabling and health.
The command bar
| Command | What it does | Greyed when (situation) | Not drawn when (role) |
|---|---|---|---|
| Enable | Lets the devices acquire the bus and locks the physical tuple. | The line is already enabled, its tuple is invalid, a scan is running, or the station refuses mutations. | Without Configure connector. |
| Disable | Closes the bus for every device on it without touching their own Enabled switches, and unlocks the tuple. | The line is off, a scan is running, or the station refuses mutations. | Without Configure connector. |
| Delete line (danger ink, on the right) | Asks first. An empty line: "Delete 'Line'? This line has no devices. This cannot be undone." A line with devices: "This also deletes its 3 devices and all of their tags." After the delete the Modbus RTU driver is selected. | A scan is running, or the station refuses mutations. | Without Configure connector. |
Right-clicking the line adds Add device before the same Enable, Disable and Delete.
The Physical line card
"One physical serial bus: the port settings every unit addressed on this line shares."
| Field | What it is | Values / default | Effect |
|---|---|---|---|
| Name | The friendly name of the bus, shown in the tree and in every device's "Serial line" field. | Required; "New line" at creation. | Editable while the line is enabled. Blank is refused: "Line name is required." The name never enters an address: a Modbus RTU device is addressed Connector.ModbusRtu.<Device>.<Tag> with no line segment. |
| Serial port | The Windows COM port: physical, virtual or redirected. A text field with a picker of the ports Windows currently reports; choosing one fills the field. Refresh re-reads the operating system's list without replacing what you typed. With nothing detected the picker shows one disabled entry, "No ports detected", and the field says "No serial ports detected. Type one manually." | Required; the first free detected port at creation. | Locked while the line is enabled. One port belongs to one line, case-insensitively, even while both are disabled: a second line on the same port is refused when saved. |
| Baud | The bus speed. | Greater than zero; 9600. | Locked while enabled. With the format it fixes the automatic inter-frame silence. |
| Serial format | Data bits, parity and stop bits. | 8N1, 8N2, 8E1, 8E2, 8O1, 8O2; 8E1. | Locked while enabled. |
| Response timeout (ms) | How long one unit may take to answer before the request fails. | 100 to 60000; 1000. | Locked while enabled. Longer timeouts accommodate slow equipment but make missing units and discovery slower to identify, as the card says. |
| Minimum transaction interval (ms) | A line-wide silence enforced from the end of one attempted transaction to the start of the next, for every unit, read and write, including timeouts and failures. | 0 to 1000; 0. | Editable while enabled; a change takes effect without cycling the port. Zero keeps the protocol minimum. Two readouts follow: Automatic, the Modbus RTU floor (3.5 characters at the configured baud and format up to 19200 baud, 1.75 ms above it) and Effective, the greater of the floor and your value, never their sum. The note says what it is for: higher values reduce throughput for every unit on the line, and it is a compatibility aid, not a repair for wiring, termination, grounding or noise. |
Three lines close the card: the line's health summary ("Online · 2/2 devices online", "Idle · no enabled devices", "Online · 1 online · 1 with issues"), which fields are editable right now ("Physical settings are editable while the line is disabled." or "Disable the line to change its physical settings. Name and transaction interval remain editable online."), and the timeout advice.
An out-of-range value is not saved and the reason lands in the feed: "Serial port is required.", "Baud rate must be greater than zero.", "Response timeout must be between 100 and 60000 ms.", "Minimum transaction interval must be between 0 and 1000 ms." A line whose tuple is invalid cannot be enabled. A save the station refuses rolls the card back to the stored values.
The Discover units card
Drawn only for Configure connector: "Sequential read-only probe on this configured physical line." Unit ID start and Unit ID end (1 to 247, ascending; 1 to 32 by default) bound a probe of every unit in the range over this line's saved tuple; Discover starts it and turns into Cancel. The line under the fields estimates the worst case ("32 probes · up to ~32.1 s, including 4.011 ms silence before each probe.") or names what is wrong with the range ("The unit-id range must be ascending."). A line that is enabled with at least one enabled device is in use, and the card says so: "This line is in use. Disable it before discovery; Ganter Lab will not interrupt or re-enable the bus automatically." A pending edit on the card is saved before the scan opens the port. The results grid, Discovered units (Unit ID, Device, Result, Add device or Open), and the scan itself are on Discovery.
The Devices card
"Unit IDs must be unique on this line. Physical settings are inherited and cannot be changed here." Add device creates a device on this line under the first free unit id from 1 to 247 and opens it ("Added device 'New device' on 'Line 1'."); it is refused with "Line 'X' already contains every valid Unit ID." when none is free, and greyed during a scan. The table lists Device, Unit ID, Tags, Health and the actions Open, Enable, Disable and Delete (the last three for Configure connector, all greyed during a scan). The device's own page shows the line and its tuple as read-only text; see Devices.
What a line does not do
A line takes no folders: its devices are filed by the line and by nothing else, and the Move to menu is not offered on them. A device cannot be moved to another line; Copy device keeps the copy on the same line under the next free unit id. The tuple cannot vary per device, and the port is never opened without a device: an enabled line with no enabled device reads Idle and holds no session, which is also what makes it safe to scan.