Implement support for broadcast

[T0RAT0RA]

Hi,

I added support for broadcast messages.

Documentation can be found here: Modbus_over_serial_line_V1.pdf (see page 7/44)

In broadcast mode, the master can send a request to all slaves.
No response is returned to broadcast requests sent by the master. The broadcast requests are necessarily writing commands. All devices must accept the broadcast for writing function. The address 0 is reserved to identify a broadcast exchange

[brainelectronics]

Can you please move this new part up to around line 105, just to not mix up any non existing order ;) I still want to keep the CRC part at the end of the file

[T0RAT0RA]

I got an error in the CI that I couldn't find a solution for. Upgrading to 6 solved the issue (locally).
I'm not familiar with your CI/CD pipeline, so not sure it won't break anything.

The error in CI:

Run rm dist/*.orig
  rm dist/*.orig
  twine check dist/*.tar.gz
  shell: /usr/bin/bash -e {0}
  env:
    pythonLocation: /opt/hostedtoolcache/Python/3.9.21/x64
    LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.9.21/x64/lib
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.21/x64/bin/twine", line 5, in <module>
    from twine.__main__ import main
  File "/opt/hostedtoolcache/Python/3.9.21/x64/lib/python3.9/site-packages/twine/__init__.py", line 43, in <module>
    __license__ = metadata["license"]
  File "/opt/hostedtoolcache/Python/3.9.21/x64/lib/python3.9/site-packages/importlib_metadata/_adapters.py", line 54, in __getitem__
    raise KeyError(item)
KeyError: 'license'
Error: Process completed with exit code 1.

[T0RAT0RA]

Hey @brainelectronics,
do you think you could have another look at the PR? :)

Thanks!