Initial version of freemodbus master port files have been added to ESP-IDF based on https://github.com/armink/FreeModbus_Slave-Master-RTT-STM32.
The overall repository license, at the time of adding these files, has been BSD 3-clause. However at that time, several port files carried LGPL license headers. As the author of these files confirmed in https://github.com/armink/FreeModbus_Slave-Master-RTT-STM32/issues/61#issuecomment-977828450, this wasn't intentional. ESP-IDF version of modbus master port has been rewritten to target FreeRTOS instead of RT-Thread, but the license headers remained from the original version. This commit corrects this, replacing the license of these files with BSD 3-clause.
add support of modbus master ascii
rename base dir name of master and slave example to be mb_slave, mb_master to avoid conflict with sdio/slave example test
add Kconfig option to enable ASCII and RTU mode separately
update ASCII options + remove cast for errors
added baudrate for examples into Kconfig
updated magic numbers for timer timeout
put ascii private definitions into one file
This example adds functionality to support basic communication in RS485 networks using Modbus protocol.
This example uses FreeModbus stack and regular UART driver API to communicate in RS485 half duplex mode.
Added initial support of modbus controller pure C api to access device parameters over Modbus transport.
Move freemodbus stack and port files into components folder
Move the modbus_controller interface into components idf folder
Source files updated after review.
Add modbus interface documentation docs/en/api-reference/protocols/modbus.rst
porttimer.c: fix bug with timer1 selected in the Kconfig
Add support of cmake system (added cmake files)
Closes https://github.com/espressif/esp-idf/issues/858
