.. _introduction:

Introduction
============

*ogamma* Modbus OPC UA Server exposes configured Modbus master devices in OPC UA server address space. Modbus data (coils and registers) are represented in the OPC UA sddress space as OPC UA variables. 
Modbus devices can be accessed by *ogamma* Modbus OPC UA Server  either over TCP/IP or serial port.

.. image:: images/ContextDiagram-2.png

Following sections describe how *ogamma* Modbus OPC UA Server can be installed, activated by license file, configured and used.

Note that after installation, it needs to be activated with license file, as described in section :ref:`license`, and configured as described in section :ref:`configure` . Note that activation of the license for the application and its configuration can be performed either by direct access and modification of files, or over OPC UA protocol, by calling custom methods. For the later, you will need to use OPC UA Client with support of calling methods. In this document we will assume that you use generic OPC UA client ``UA Expert`` from Unified Automation, which can be downloaded from https://www.unified-automation.com/downloads/opc-ua-clients.html Note that registration is required.

By default, *ogamma* Modbus OPC UA Server is configured to accept only secured connections from clients with trusted certificates. If you choose to configure it over OPC UA connection, to allow initial connection configuration needs temporarily to be changed either to allow none-secure connections, or accept any certificate, as described in the section :ref:`configure`.