This example demonstrates using of FreeModbus stack port implementation for ESP32. The external Modbus host is able to read/write device parameters using Modbus protocol transport. The parameters accessible thorough Modbus are located in `mb_example_common/modbus_params.h\c` files and can be updated by user.
These are represented in structures holding_reg_params, input_reg_params, coil_reg_params, discrete_reg_params for holding registers, input parameters, coils and discrete inputs accordingly. The app_main application demonstrates how to setup Modbus stack and use notifications about parameters change from host system.
The FreeModbus stack located in `components/freemodbus` folder and contains the `/port` folder inside with FreeModbus stack port for ESP32. There are some parameters that can be configured in KConfig file to start stack correctly (See description below for more information).
The modbus_master example application configured as described in its README.md file and flashed into ESP32 WROVER-KIT board.
Note: The ```Example Data (Object) Dictionary``` in the modbus_master example can be edited to address parameters from other slaves connected into Modbus segment.
Note: The GPIO22 - GPIO25 can not be used with ESP32-S2 chip because they are used for flash chip connection. Please refer to UART documentation for selected target.
Define the ```Modbus communiction mode``` for slave in Kconfig - CONFIG_MB_COMM_MODE (must be the same for master and slave application).
Set ```Modbus slave address``` for the example application (by default for example script is set to 1).
The communication parameters of freemodbus stack (Component config->Modbus configuration) allow to configure it appropriately but usually it is enough to use default settings.
See the help strings of parameters for more information.
Setup ESP32 WROVER-KIT board and set modbus_master example configuration as described in its README.md file.
Setup one or more slave boards with different slave addresses and connect them into the same Modbus segment (See configuration above).
Note: The ```Modbus communiction mode``` parameter must be the same for master and slave example application to be able to communicate with each other.
The output lines describe type of operation, its timestamp, modbus address, access type, storage address in parameter structure and number of registers accordingly.
