Peter M. Groen / libmodbus

Thanks to Stefan Finzel for the bug report

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

Thanks to Thomas Stalder and Torello Querci for the report.

Original patch for new connect function by Thomas Stalder.

Thanks to Bernhard Agthe.

- export new symbols to create specific behavior (RTU)
- the flag can't only be set by slaves
- new tests

Warning, modbus_receive returns 0 when a query is ignored.

- function removed from TCP and RTU code and from backend structure
- updated documentation
- updated examples

- remove static variable in the library

libabc is a really good source of inspiration!
https://git.kernel.org/?p=linux/kernel/git/kay/libabc.git

The serial mode and rts flags are now initialized in new function.
Original patch provided by Jaime Alberto Silva
<jaime@sgautomatizacion.com>.

- new function _modbus_rtu_pre_check_confirmation
- new special test value to trigger an invalid response
- add unit test to cover invalid TID too

Thanks to Andrea Mattia

Original patch provided by Thomas Stalder.

Thanks to Pavel Mazniker for the report.

- avoid export of _modbus_rtu_set_rts and change its name to avoid
  confusion
- namespace RTU functions and constants
- use_rts is renamed rts
- add missing '_' in function name
- remove useless debug message in usual write
- wrong message about 'not supported'
- add check for TIOCM_RTS support
- block RTS flow control when not available

bit is used HIGH to able to transmit, or LOW.

Bonus side effect: the integer isn't present anymore when TIOCSRS485
isn't supported on non Win32 platforms.

When there's no RS485 support available (e.g. on Win32), the modbus_rtu_t
data structure does not have the serial_mode member. It therefore must
not be used in modbus_rtu_get_serial_mode() if HAVE_DECL_TIOCSRS485 is
not defined. Fixes Win32 build with recent versions of libmodbus.

The ENOTSUP error code is not defined on Win32. However we can simply
use an equivalent from the Windows Socket API (WSA). Fixes Win32 build
with recent versions of libmodbus.

Add macros in libmodbus.txt and:
- modbus_get_byte_from_bits.txt
- modbus_get_float.txt
- modbus_reply.txt
- modbus_reply_exception.txt
- modbus_set_bits_from_byte.txt
- modbus_set_bits_from_bytes.txt
- modbus_set_float.txt