Device DataReader

DataReader

This page is generated from the Unity twin. Published from _docs/context/devices/datareader.md — edit it there, not here. Changes made in the wiki are overwritten on the next sync.

A code reader or camera: on command, reads a number carried by the part in front of it and hands it to the PLC.

Twin device type · twin FB FB_Camera · 3 instances in FG_01, FG_02, FG_05 · Unity component Preliy.Demo.DataReader

What it is

The station that answers "which part is this?". In the real cell it is a camera or a barcode scanner; the part carries an identity, and the reader turns it into a number the control program can act on. This machine has three of them — one identifies, one inspects, one checks a cap.

Open Commissioning ships a data reader of its own; this project uses a variant of it that adds the PLC handshake below.

What the PLC sees

Symbol	Meaning
Control.0	Enable
Control.1	Trigger — read now
Status.0	Enabled, echoed back
Status.1	Triggered, echoed back
StatusData	The value read, as a 64-bit number

The Unity component drives exactly these. The result-valid and result-OK bits a control program waits on are added by the reader's function block in the simulation project, on top of this — so the full protocol a PLC sees is the one written on the device's own page and in the FG_01 behaviour contract.

How the twin models it

The reader is a volume in the scene, like a sensor. A part carries named data with it, and the reader is configured with the name of the field to read. On a trigger it looks up that field on whatever part is currently in front of it; dropping the trigger clears the result. If nothing is there, or the part carries no such field, the read fails and is logged — it does not invent a value.

Watch out

A result is only meaningful while the part is still there. The value is cleared when the trigger drops or the part leaves, so a program that triggers and reads the answer three steps later may find it gone.

In this machine

Signal — Enable, then trigger; reads back Ready, Busy, ResultValid and ResultOK. The twin echoes the two control bits and hands over the datum; the verdict is synthesised in OC_SIM FB_Camera.

There are 3 of them, in FG_01, FG_02, FG_05:

Device	Twin PLC path	Group
P_Camera	MAIN.FG_01.P_Camera	FG_01
P_Camera	MAIN.FG_02.P_Camera	FG_02
P_Camera	MAIN.FG_05.P_Camera	FG_05

Control implementations

The twin is master for structure, and that is all this page states. Which control function block each instance becomes, its process-image members and its published HMI struct is the control platform's own knowledge base:

• Beckhoff
• Siemens — no knowledge base published yet