Update brailleNote driver to use hwIo and thus make it thread safe.

[jcsteh]

Link to issue number:

Fixes #7574.

Summary of the issue:

From #7574 (comment):

The current HumanWare BrailleNote driver, although native, does not yet utilize the hwIo module. This driver should be updated to support braille display auto detection, since we agreed in #1271 that this will be a prerequisite.

Description of how this pull request fixes the issue:

Updates the driver to use hwIo.Serial.

Testing performed:

I don't have a BrailleNote, so couldn't test this. However, @josephsl confirmed in #7574 (comment) that it works for him.

Known issues with pull request:

None known.

Change log entry:

Not user visible at this stage, so no change log entry. However, this can safely be merged before braille display detection. It should provide a slight performance improvement when there are lots of writes and should mean we aren't waking our main thread as often due to continual polling.

[LeonarddeR]

Is there a particular reason why you did not do a self._serial.close() in the finally block of terminate, like this is executed for Baum and brailliantB? I'm afraid this can lead to unexpected issues when you terminate the display and running init again without destroying the BrailleDisplayDriver object.

[jcsteh]

It does call close in the finally block. I think you're confused by the fact that the diff shows the removal of the _closeComPort method, except for the last line, which is the bit that calls self._serial.close.