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.
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.
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.
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.