DALI · Interface guide
Modbus
Read sensors and meters over Modbus TCP, RS232 and RS485, and let a SCADA or another logger read the station's values as a Modbus slave.
The Modbus page sets up the station's Modbus connections. The station can be a master, asking sensors for their readings, and a slave, answering another system that asks it for its values. Each bus has its own tab.
Who can open it: Admin and Factory.
| Tab | Role | Connection |
|---|---|---|
| TCP Master | Master | Modbus TCP over the network |
| RS232 Master | Master | The RS232 port |
| RS485 Master | Master | The first RS485 port |
| RS485-2 Master | Master | The second RS485 port |
| TCP Slave | Slave | Modbus TCP over the network |
| RS232 Slave | Slave | The RS232 port |
| RS485 Slave | Slave | The RS485 port |
A master tab holds queries. A query is one request to one device: "read this many registers from this address on this slave". The readings a query brings back become useful once you map them to parameters on the Parameters page.
Master tabs
Top of the tab
| Control | Allowed values | What it does |
|---|---|---|
| Enable | On or off | Turns polling on this bus on or off. Saves as soon as you flip it. |
| Poll Delay (s) | 0.01 to 10 | Pause between one polling cycle and the next. Saves itself a second after you change it. |
| Relax response Unit-ID check | On or off. TCP Master only, on by default. | When on, the station accepts a reply even if the device puts a different unit ID in it. The data is still stored under the Slave ID you set, so it cannot mix up two devices. Many TCP devices and gateways reply with a fixed or arbitrary unit ID. |
Query list
A table of the bus's queries: number, Slave ID, the IP address and port (TCP) or baud rate and data/parity/stop bits (serial), function code, address, quantity, response timeout, retries, TX mode (RS485 Master only) and whether it is active.
Each row has Edit and Del. + Add Query opens an empty query form. The counter next to it shows how many of the 50 allowed queries are used.
Query form
| Field | Allowed values | What it does |
|---|---|---|
| Slave ID | 1 to 255 | The address of the device on the bus. 0 (broadcast) is not allowed. On RS232 Master every query uses the same Slave ID as the first one, because only one device can be on an RS232 line. |
| Function Code | 3 (Read Holding Registers) or 4 (Read Input Registers) | Which kind of register to read. |
| Start Address | 0 to 65535 | First register to read. |
| Quantity | 1 to 50 | How many registers to read. Address plus quantity cannot go past 65535. |
| Slave IP / Domain | An IPv4 address or a host name, up to 64 characters. TCP only. | Where the device is on the network. The box turns green when the value looks valid. |
| Port | 1 to 65535, default 502. TCP only. | The device's Modbus TCP port. |
| Connect Timeout (s) | 1 to 60, default 5. TCP only. | How long to wait for the connection. |
| Baud Rate | 9600, 19200, 38400, 57600 or 115200. Serial only. | Line speed. Must match the device. |
| Parity | None, Even or Odd. Serial only. | Must match the device. Data bits are always 8. |
| Stop Bits | 1 or 2. Serial only. | Must match the device. |
| Response Timeout (s) | 0.1 to 5, default 1 | How long to wait for the device to answer. |
| Retries | 0 to 5, default 1 | How many more times to ask after a failed attempt. |
| Active | Yes or No | A query set to No stays in the list but is not polled. |
| TX Mode | Sensor (hold) or Xtreme (toggle). RS485 Master only. | How the station drives the RS485 line. Sensor keeps the transmitter held, which third-party sensors such as tilt sensors need. Xtreme switches it for each query, for other Aeron loggers on the bus. |
When you type a Slave ID that another query already uses, the form copies that query's connection settings for you.
Save Query checks and saves the query. Cancel closes the form without saving.
One device, one address
On TCP Master, every query with the same Slave ID must point at the same IP address and port. If you change the address of one, the page lists the others and asks whether to move them too. Saying no cancels the save.
Import and export queries
Three buttons above the tabs work across all master buses at once.
| Button | What it does |
|---|---|
| Download Template | Downloads a CSV template with instructions and sample rows. |
| Export Queries (CSV) | Downloads the queries now on the station in the same format, to edit and import back. |
| Import Queries (CSV) | Opens the import window. |
The CSV has one query per row. The Type column sends each row to its bus: TCP, RS232, RS485 or RS485_M2 (the second RS485 port). The other columns are InUse, SlaveID, FunctionCode, Address, Quantity, BaudRate, Parity, Stopbits, txMode, SlaveIpAddress, SlavePort, ConnectTimeout, ResponseTimeout and Retries, with the same allowed values as the form. Serial rows leave the TCP columns blank, and TCP rows leave the serial columns blank. Lines starting with # are ignored.
In the import window:
| Control | What it does |
|---|---|
| Conflict mode | Add only (skip duplicates), Update existing + add new, or Replace all (remove queries not in this file). |
| CSV file | The file to import. |
| Import | Checks every row and imports the good ones. A table shows the result of each line. |
| Retry failed | Tries the failed rows again. |
| Download failed rows | Saves the rows that failed, to fix and import again. |
In Replace mode the window first lists the queries that the file would delete, and imports only after you press Delete listed queries & import.
Slave tabs
A slave tab lets another system read the station's values.
| Field | Allowed values | What it does |
|---|---|---|
| Enable | On or off | Turns the slave on or off. The toggle saves by itself. |
| Ignore Slave ID in request | On or off. TCP Slave only, on by default. | When on, the station answers whatever unit ID the master sends. Many SCADA systems send a fixed or arbitrary unit ID. |
| Slave ID | 1 to 255, default 1 | The station's own address. |
| Port | 1 to 65535, default 502. TCP only. | The port the station listens on. |
| Baud Rate, Parity, Stop Bits | As for the master tabs. Serial only. | Must match the master that reads the station. |
Save stores the settings.
Under the form, Slave Information shows the settings in use: Slave ID, whether the slave ID is checked, the protocol (Modbus TCP or Modbus RTU), and the function code the station answers, which is always 4 (Read Input Registers). It also shows the Memory Map: the time, GPS position and network status first, then each parameter as a 32-bit float in two registers, in the order set on the Parameters page. The full layout is on Modbus slave register map.
RS232 is shared with the service console
The RS232 port is also the station's service console. Turning on RS232 Master or RS232 Slave takes the port over and switches the console off.
Messages you may see
| Message | What it means |
|---|---|
| Query already exists (#3). Duplicate not saved. | Another query on this bus reads exactly the same thing. |
| Maximum 50 queries reached. | The bus is full. Delete a query or use another bus. |
| Cannot delete. At least one query must remain. | Every master bus keeps at least one query. Set it to Active: No instead. |
| Slave ID must be between 1 and 255 (0 is the reserved broadcast address, not supported) | Enter an address from 1 to 255. |
| Enter a valid IP address or hostname for Slave IP / Domain | The address is not a valid IPv4 address or host name. |
| Quantity must be between 1 and 50 registers | Split the read into two queries. |
| Response timeout must be between 0.1 and 5 seconds | Enter a value in range. |
| Poll delay must be between 0.01 and 10 seconds | Enter a value in range. |
| Save cancelled: IP/Port unchanged. | You said no to moving the other queries for the same Slave ID. |