Copyright (c) 2001-2003,2016 Mario de Sousa (msousa@fe.up.pt)
This file is part of the Modbus library for Beremiz and matiec.
This Modbus library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this Modbus library. If not, see http://www.gnu.org/licenses/.
This code is made available on the understanding that it will not be
used in safety-critical situations without a full and competent review.

Modbus Protocol Libraries

This directory contains the libararies that implement the modbus protocol stack.

This protocol has been implemented as a two layer stack. Layer two includes the mb_master and the mb_slave protocols. Layer one is composed of the mb_rtu, mb_ascii and mb_tcp protocols.

Layer1 protocols all implement the same interface, defined in mb_layer1.h Layer2 protocols implement different interfaces, defined in mb_master.h and mb_slave.h

Which layer1 protocol that will be used by the program will depend on which layer1 protocol implementation is linked to the final binary/executable. It is not possible to define during run-time which layer1 protocol is to be used. Each compiled program can only support a single layer1 protocol.

Users of these libraries should only use functions defined in the layer2 protocol header files (i.e. mb_master.h and mb_slave.h)

If writing a program that will simultaneously be a master and a slave, then only use the mb_slave_and_master.h header file! In this case, do not forget to link the final binary to both the master and slave protocol implementations (as well as the chosen layer1 protocol implementation).

        ------------------------------------------
        |                    |                   |

layer 2 | mb_master.h | mb_slave.h | | mb_master.c | mb_slave.c | | | | |----------------------------------------| | mb_layer1.h | Layer 1 | | | | | mb_rtu.c | mb_ascii.c | mb_tcp.c | | | | | ------------------------------------------