Services / Technology

How USCADA works

A technical overview for engineers: how a station sends data, how the server decodes it and who sees the result.

1. Station
2. TCP
3. USCADA server
4. Project database
5. WebSocket
6. Browser

A value’s path

1. The station sends a frameThe equipment opens a TCP connection to the USCADA server and sends -TD frames.
2. The server decodes itBy UID the server finds the device profile, splits the data into tags and checks the rules.
3. The data is storedValues, events and trends go into a separate project database.
4. The browser updatesThe user’s screen gets changes over WebSocket, with no page reload.

Frame format

A frame is text: fields are written as hexadecimal digits and the frame ends with \r.

-TD{SN}{LEN_UID}{UID}{LEN_DATA}{DATA}\r

An example from the simulator, spaces added for reading: -TD 01 10 4C11…6830 04 03CF0002 \r.

Commands to the station go over the same connection in a mirror -TC frame with the same fields. The station parses incoming and outgoing frames with one parser.

UID profiles

A UID profile describes a device: which tags the data holds and how to show them. Identical stations differ only by their SN number and share one profile, so a profile change applies to all its stations. A profile can be exported and imported as a CSV file.

Connection loss

If a station is silent longer than the set time, the server records a connection loss event. The default is 2 minutes and it can be changed per station. When frames arrive again, the event closes.

Access and data

• Each project has a separate database
• Roles define what a user can change, and groups define which stations they see
• A command has a priority: a user with a lower priority cannot send it
• The public site runs over HTTPS

What the equipment needs

Connection

A TCP/IP client that can reach the USCADA server

Format

The -TD frames described above

Other equipment

Capturing protocols and connecting devices that work differently are part of our engineering services