Add deassert_rts_dtr option to force RTS/DTR low when using miniterm

[agners]

What does this implement/fix?

By default RTS/DTR seem to be True (-> 0 since low active). Most ESP32
boards have a pair of transistors to keep Reset/strapping GPIO as-is
when both RTS/DTR are either True or False.
See: https://raw.githubusercontent.com/nodemcu/nodemcu-devkit/master/Documents/NODEMCU_DEVKIT_SCH_BIG.png

If RTS/DTR are connected to Reset/strapping GPIO directly we'd prefer to have
RTS/DTR False (-> 1 since low active). In theory, we could set it to False
always, since the above mentioned logic makes sure nothing happens if both
signals are False.

However, on some platforms (e.g. Linux) setting them to False leads to toggling
when opening which causes a reset.

This introduces a new config "low_rts_dtr" which allows to set the
signals low if required by the board.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Related issue or feature (if applicable): fixes esphome/issues#1382

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#1348

Test Environment

• ESP32
• ESP8266

Example entry for config.yaml:

logger:
  deassert_rts_dtr: true

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.

[probot-esphome]

Hey there @esphome/core, mind taking a look at this pull request as its been labeled with an integration (logger) you are listed as a codeowner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[OttoWinter]

LGTM 👍 Docs need to be updated though

[agners]

Now that I write the documentation, I don't like low_rts_dtr: RTS and DTR are often low active in TTL. So setting the signals to false leads to a high voltage level on the effective TTL lines. How about deassert_rts_dtr?

[OttoWinter]

How about deassert_rts_dtr?

Works for me 👍

[jesserockz]

Worked for my C3