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Modbus

This directory contains a port of last open source version of FreeModBus (BSD
license). The code in this directory is a subset of FreeModBus version 1.5.0
(June 6, 2010) that can be downloaded in its entirety from
http://developer.berlios.de/project/showfiles.php?group_id=6120.

Includes extensions to support RTU master mode by Armink(383016632@qq.com):
https://github.com/armink/FreeModbus_Slave-Master-RTT-STM32. Ported to NuttX by
Darcy Gong.


Directory Structure / Relation to freemodbus-v1.5.0

The original FreeModBus download consists of several directories. This subset
takes only the contents of one directory, modbus/, that implements the core
modbus logic and integrates that directory into the NuttX build system. The
mapping between freemodbus-v1.5.0 and the nuttx directories is shown below:

--------------------------- ----------------------------------------------
freemodbus-v1.5.0           NuttX
--------------------------- ----------------------------------------------
All top level .txt files    Not included
demo/                       Not included. This directory contains demo
                            and porting code for a variety of platforms.
                            The NuttX demo was ported from the LINUX
                            demo in this directory and can be found at
                            apps/examples/modbus.
doc/                        Not included. This directory contains Doxygen
                            support files.
modbus/                     Included in its entirety in various locations:
        ascii                  apps/modbus/ascii
        functions              apps/modbus/functions
        include                apps/include/modbus
        mb.c                   apps/modbus/mb.c
        rtu                    apps/modbus/rtu
        tcp                    apps/modbus/tcp
tools/                      Not included. This directory contains Doxygen
                            tools.
--------------------------- ----------------------------------------------


So this directory is equivalent to the freemodbus-v1.5.0/modbus directory
except that (1) it may include modifications for the integration with NuttX and
(2) the modbus/include directory was moved to apps/modbus.

The original, unmodified freemodbus-v1.5.0 was checked in as SVN revision
4960.

The other directory here, nuttx/, implements the NuttX modbus interface. It
derives from the freemodbus-v1.5.0/demo/LINUX/port directory.


Configuration Options

In the original freemodbus-v1.5.0 release, the FreeModBus configuration was
controlled by the header file mbconfig.h. This header file was eliminated
(post revision 4960) and the FreeModBus configuration was integrated into the
NuttX configuration system.

The NuttX-named configuration options that are available include:


CONFIG_MODBUS – General ModBus support.

CONFIG_MB_ASCII_ENABLED – Modbus ASCII support.

CONFIG_MB_ASCII_MASTER – Modbus ASCII master support.

CONFIG_MB_RTU_ENABLED – Modbus RTU support.

CONFIG_MB_RTU_MASTER – Modbus RTU master support.

CONFIG_MB_TCP_ENABLED – Modbus TCP support.

CONFIG_MB_ASCII_TIMEOUT_SEC – Character timeout value for Modbus ASCII. The
character timeout value is not fixed for Modbus ASCII and is therefore a
configuration option. It should be set to the maximum expected delay time of
the network. Default: 1.

CONFIG_MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS – Timeout to wait in ASCII prior
to enabling transmitter. If defined the function calls vMBPortSerialDelay
with the argument CONFIG_MB_ASCII_TIMEOUT_WAIT_BEFORE_SEND_MS to allow for a
delay before the serial transmitter is enabled. This is required because some
targets are so fast that there is no time between receiving and transmitting
the frame. If the master is too slow with enabling its receiver then it will
not receive the response correctly.

CONFIG_MB_FUNC_HANDLERS_MAX – Maximum number of Modbus functions codes the
protocol stack should support. The maximum number of supported Modbus
functions must be greater than the sum of all enabled functions in this file
and custom function handlers. If set too small, adding more functions will
fail.

CONFIG_MB_FUNC_OTHER_REP_SLAVEID_BUF – Number of bytes which should be
allocated for the Report Slave ID command. This number limits the maximum size
of the additional segment in the report slave id function. See
eMBSetSlaveID() for more information on how to set this value. It is only
used if CONFIG_MB_FUNC_OTHER_REP_SLAVEID_ENABLED is set to 1.

CONFIG_MB_FUNC_OTHER_REP_SLAVEID_ENABLED – If the Report Slave ID function
should be enabled.

CONFIG_MB_FUNC_READ_INPUT_ENABLED – If the Read Input Registers function
should be enabled.

CONFIG_MB_FUNC_READ_HOLDING_ENABLED – If the Read Holding Registers function
should be enabled.

CONFIG_MB_FUNC_WRITE_HOLDING_ENABLED – If the Write Single Register function
should be enabled.

CONFIG_MB_FUNC_WRITE_MULTIPLE_HOLDING_ENABLED – If the Write Multiple
registers function should be enabled.

CONFIG_MB_FUNC_READ_COILS_ENABLED – If the Read Coils function should be
enabled.

CONFIG_MB_FUNC_WRITE_COIL_ENABLED – If the Write Coils function should be
enabled.

CONFIG_MB_FUNC_WRITE_MULTIPLE_COILS_ENABLED – If the Write Multiple Coils
function should be enabled.

CONFIG_MB_FUNC_READ_DISCRETE_INPUTS_ENABLED – If the Read Discrete Inputs
function should be enabled.

CONFIG_MB_FUNC_READWRITE_HOLDING_ENABLED – If the Read/Write Multiple
Registers function should be enabled.


See also other serial settings, in particular:


CONFIG_SERIAL_TERMIOS – Serial driver supports termios.h interfaces
(tcsetattr, tcflush, etc.). If this is not defined, then the terminal
settings (baud, parity, etc.) are not configurable at runtime; serial streams
will not be flushed when closed.


Note

The developer of FreeModBus, Christian Walter, is still developing Modbus
libraries, although they are now commercial. See
http://www.embedded-solutions.at/ for further information.