FINS Driver

dc3-driver-fins onboards Omron PLCs into IoT DC3 over the FINS protocol——it periodically reads PLC memory-area values by word address, and supports commands that write values back to memory areas.

FINS (Factory Interface Network Service) is the native communication protocol of Omron PLCs, widely used across the CP/CJ/CS series. This driver acts as a FINS client, actively connecting to the PLC over TCP, then reading and writing per the memory area and word address configured on each Point. It builds FINS frames by hand (no third-party protocol library) and supports the D, W, H, and C memory areas.

• Driver name / code: Omron FINS Driver / FinsDriver
• Type: DRIVER_CLIENT (actively connects to the PLC)

A few FINS concepts first

Memory Area: a region of PLC data partitioned by purpose——D (data memory, the most common), W (work), H (holding), C (counter). Word Address: an offset within a memory area in units of one "word" (16 bits), e.g. D100 is the 100th word of the D area. Node/Unit number: the source/destination addresses used to reach a PLC on the FINS network; for a single direct connection these usually stay at their defaults.

Driver configuration (device-level driver-attribute)

When onboarding a FINS PLC, fill these Attributes on the Device:

Attribute	code	Type	Default	Description
Host	host	STRING	127.0.0.1	PLC host address
Port	port	INT	9600	FINS port (standard 9600)
Protocol	protocol	STRING	TCP	Transport protocol
Source Node	sourceNode	INT	1	FINS source node number
Dest Node	destNode	INT	2	FINS destination node number
Source Unit	sourceUnit	INT	0	FINS source unit number
Dest Unit	destUnit	INT	0	FINS destination unit number
Timeout	timeout	INT	5000	Request timeout (milliseconds)

Point configuration (point-attribute)

Fill these on each acquisition Point:

Attribute	code	Type	Default	Description
Memory Area	memoryArea	STRING	D	Memory area, D/W/H/C
Address	address	INT	0	Word address within the memory area
Data Type	dataType	STRING	UINT16	INT16/UINT16/INT32/UINT32/FLOAT/STRING/BCD
Bit Position	bitPosition	INT	0	Bit offset within the word (unused on the current read path; treated as 0)

The current read path only supports 16-bit types; dataType does not decide how many words are read

A read always fetches exactly 1 word (2 bytes), regardless of dataType. So only INT16/UINT16 read back correctly; INT32/UINT32/FLOAT/STRING/BCD are protocol semantics whose implementation is still pending——they need 4 bytes or more, and decoding a 2-byte big-endian read triggers a BufferUnderflow, so no value is actually produced today. STRING/BCD likewise only receive 2 bytes. The driver decodes the returned bytes Big-Endian; the Point's data type (Point's pointTypeFlag) should match the dataType set here.

Write command configuration (command-attribute)

Writable points additionally need these on the write command:

Attribute	code	Type	Default	Description
Memory Area	memoryArea	STRING	D	Memory area, D/W/H/C
Address	address	INT	0	Word address within the memory area
Data Type	dataType	STRING	UINT16	Data type of the written value

Acquisition and health

• Acquisition cycle: default cron 0/30 * * * * ? (reads once every 30 seconds).
• Custom task: default cron 0/5 * * * * ? (the FINS driver currently uses no custom task; this schedule slot is reserved).
• Health / online: the device health check defaults to cron 0/15 * * * * ? with a lease timeout of 45 seconds——the driver decides online status by whether the TCP connection is alive; for the online state mechanism see Device.

Minimal onboarding example

Onboard an Omron PLC at IP 192.168.1.20:9600 and acquire one 16-bit integer at D100:

1. Create a Device with Omron FINS Driver, set driver attributes host=192.168.1.20 and port=9600, and leave the rest (protocol, node/unit numbers, timeout) at their defaults.
2. Add a Point (pointTypeFlag=INT, READ_ONLY) to the Profile bound to the device, with point attributes memoryArea=D, address=100, dataType=INT16.
3. Start the driver; within 30 seconds the D100 value appears in PointValue.

Pitfalls

address is a word address, not a region-prefixed string

address takes only the numeric offset within the memory area. To read Omron's familiar D100, set memoryArea=D and address=100——do not put D100 as a whole into address. The area is specified separately by memoryArea.

32-bit writes are currently encoded as integers

The write command parses INT32/UINT32/FLOAT all via Integer.parseInt before writing 4 big-endian bytes. That means a FLOAT write expects the integer form of the bit pattern, not decimal text like 12.5——confirm the format of the dispatched value matches what the PLC expects before writing floats.

One driver instance can serve multiple PLCs

A single FINS driver process can serve multiple devices, each holding its own TCP connection (cached by device ID). Multiple PLCs are distinguished by their own host and destNode.

Further reading

• Driver — the general driver model and registration mechanism
• Attribute & Config — where attributes like host / memoryArea come from across the three layers
• Device Onboarding — a full onboarding walkthrough
• Modbus TCP Driver — another common industrial TCP protocol