gologix

gologix is a communication driver written in native go that lets you easily read/write values from tags in Rockwell Automation ControlLogix, and CompactLogix PLC's over Ethernet I/P using GO. PLCs that use CIP over Ethernet/IP are supported (controllogix, compactlogix, micro820). Models like PLC5, SLC, and MicroLogix that use PCCC instead of CIP are not supported.

It is modeled after pylogix with changes to make it usable in go.

Your First Client Program:

There are a few examples in the examples folder, here is an abriged version of the SimpleRead example. See the actual example for a more thorough description of what is going on.

package main

import (
	"fmt"
	"gologix"
)

func main() {
	client := gologix.NewClient("192.168.2.241")
	err := client.Connect()
	if err != nil {
		log.Printf("Error opening client. %v", err)
		return
	}
	defer client.Disconnect()

	var tag1 int16
	err = client.Read("testint", &tag1)
	if err != nil {
		log.Printf("error reading testint. %v", err)
        return
	}
	log.Printf("tag1 has value %d", tag1)
}

Your First Server Program:

There are a few examples in the examples folder, here is an abriged version of the Server_Class3 example. See the actual example(s) for a more thorough description of what is going on. Basically it listens to incoming MSG instructions doing CIP Data Table Writes and CIP Data Table Reads and maps the data to/from an internal golang map. You can then access the data through that map as long as you get the lock on it.

package main

import (
	"fmt"
	"gologix"
	"os"

)

func main() {
	r := gologix.PathRouter{}

	p1 := gologix.MapTagProvider{}
	path1, err := gologix.ParsePath("1,0")
	if err != nil {
		log.Printf("problem parsing path. %v", err)
		os.Exit(1)
	}
	r.AddHandler(path1.Bytes(), &p1)


	s := gologix.NewServer(&r)
	go s.Serve()

	t := time.NewTicker(time.Second * 5)
	for {
		<-t.C
		p1.Mutex.Lock()
		log.Printf("Data 1: %v", p1.Data)
		p1.Mutex.Unlock()


	}
}

Other Features

Can behave as a class 1 or class 3 server allowing push messages from a PLC (class 3 via MSG instruction) or implicit messaging (class 1). See the *server examples.

You can read/write multiple tags at once by defining a struct with each field tagged with gologix:"tagname". see MultiRead in the examples directory.

To read multiple items from an array, pass a slice to the Read method.

To read more than one arbitrary tags at once, use the ReadList method - the first parameter is a slice of tag names and the second parameter is a slice of each tags type.

You can read UDTs in if you define an equivalent struct to blit the data into. Arrays of UDTs also works. (see limitation below about UDTs with packed bools)

There is also a Server type that lets you recive msg instructions from the controller. See "Server" in the examples folder. It currently handles reads and writes of atomic data types (SINT, INT, DINT, REAL). You could use this to create a "push" mechanism instead of having ot poll the controller for data changes.

Limitations

You cannot write multiple items from an array at once yet, but you can do them piecewise if needed.

You can write to BOOL tags but NOT to bits of integers yet (ex: "MyBool" is OK, but "MyDint.3" is NOT). You can read from either just fine. I think there is a "write with mask" that I'll need to implement to do this.

If the UDT you're reading has bools packed in it, you'll need to use the ReadPacked() function instead of client.Read(). The plan is to eventually migrate this functionality to client.Read automatically.

No UDTs or arrays in the server yet. This will eventually be implemented and that will greatly improve functionality.

License

This project is licensed under the MIT license.

Acknowledgements

• pylogix
• go-ethernet-ip