LOGO! 0BA7/0BA8

LOGO is a small Siemens PLC suited for implementing simple automation tasks in industry and building management systems.

It’s very user friendly and the last model is equipped with an Ethernet port for both programming and data exchange.

The Snap7 focus is on to S7300/400 systems, but due to several requests, i decided to manage this PLC as well.

Communication

Due to its architecture, the LOGO communication is different from its Siemens cousins.

It implements two Ethernet protocols, the first that we can call PG protocol, is used by the software LOGO Comfort (the developing tool) to perform system tasks such as program upload/download, run/stop and configuration.
The second, used for data exchange, is the well-known (from the Snap7 point of view) S7 Protocol.

They are very different, and the first is not covered by Snap7 because is a stand-alone protocol that is not present, Is far I know, in different contexts.

Although LOGO uses the S7 Protocol, some small changes (new connection functions added) were needed in Snap7 to manage it as PLC Server by a Snap7Client.

You can use LOGO as Client connecting it to a Snap7Server or you can connect a Snap7Client to a LOGO set as Server.

Finally, to communicate with LOGO, the Ethernet connections must be designed with LOGO Comfort in advance.
Of course I will show you how.

For both type of communication (Client-Server or Server-Client) LOGO must be set as MASTER (i.e. NORMAL mode as LOGO Comfort says).

I assume that your LOGO Comfort is already set and connected to the LOGO.

LOGO as Server

Configuring a server connection allows you to connect LOGO with Snap7Client for reading and writing the memory just like an HMI panel would do.

· In the Tools menu choose the Ethernet Connections item.

· Right click on ”Ethernet Connections” and click ”Add connections” to add a connection

· Double-click the new connection created and edit its parameters selecting Server Connection.

Note:

1. “Connect with an operator panel” checkbox can be checked or unchecked.

2. If you uncheck “Accept all connections” you must specify the PC address (for now I suggest you to do it checked).

You can chose for Remote TSAP the same value of the Local TSAP, in the example I used two different values to remark (as you will see) the crossing parameters.

· Confirm the dialog, close the connection editor and download the configuration into the LOGO.

· The LOGO is ready, to test it run the new ClientDemo, insert the LOGO IP Address and select the TSAP Tab for the connection as in figure.

Notice that the Local TSAP of the Client corresponds to the Remote TSAP of the LOGO and vice-versa. This is the key concept for the S7 connections.

The LOGO memory that we can Read/Write is the V area that is seen by all HMI (and Snap7 too) as DB 1.
Into it are mapped all LOGO resources organized by bit, byte or word.

There are several tutorials in the Siemens site that show how to connect an HMI (via WinCC flexible or TIA) to the LOGO and the detailed map.
Please refer to them for further informations.

Finally, to connect to the LOGO by program with the same parameters of above:

Client->SetConnectionParams(“192.168.0.73”, 0x0300, 0x0200); // C++

Client->Connect();

Client.SetConnectionParams(“192.168.0.73”, 0x0300, 0x0200); // C#

Client.Connect();

Client.SetConnectionParams(‘192.168.0.73’, $0300, $0200); // Pascal

Client.Connect;

LOGO as Client

LOGO can work as Client in two way :

1. Explicit - using a client connection.

2. Implicit - via Network I/O blocks.

In both cases you can connect LOGO to a Snap7Server that acts like a slave.

Client connection

· In the Tools menu choose the Ethernet Connections item.

· Right click on ”Ethernet Connections” and click ”Add connections” to add a connection

· Double-click the new connection created and edit its parameters selecting Client Connection.

· Insert the Server IP Address, as TSAP you can use whatever you want, since Snap7Server doesn’t care of it.

· In the second area you can specify the data exchange area.

· As usual, confirm everything and download the configuration into the LOGO.

At this point you can run the Server Demo, and with the above configuration you should see something similar to this :

Four bytes of read request and one byte of write request, as we expected.

Network I/O Blocks

Open a Diagram and, as example, create a “loopback” between a network input and a network output.

Each network node requests a parametrization as in figure.

Here our LOGO sees Snap7Server as a LOGO Slave.

And this is what Snap7Server should show us:

Two bytes of read request and two byte of write request, as we expected.

Finally this is the connections editor of LOGO!Soft Comfort 8 (different window but absolutely the same concept)

BLOCK	VM ADDRESS START	VM ADDRESS END	FIELD LENGTH (BYTE)
I	1024	1031	8
AI	1032	1063	32
Q	1064	1071	8
AQ	1072	1103	32
M	1104	1117	14
AM	1118	1245	128
NI	1246	1261	16
NAI	1262	1389	128
NQ	1390	1405	16
NAQ	1406	1469	64