fix stepper jump back with small steps

[0xDRRB]

What does this implement/fix?

Sometimes with a reduced number of steps the stepper motor jumps in the opposite direction (clockwise) before turning in the right direction (counterclockwise). This only happens in case of counterclockwise rotation. Reducing max_speed does not fix the problem.

It turns out that the direction pin state change is too fast. I added a delay of 50µs and everything is back to normal (jump is still here with 5µs).

The problem was seen with a Wemos D1 mini connected to a cheap controller like this.
Driving the controller directly with Arduino code did not cause the problem to appear. It's just a simple timing issue.

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

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040

Example entry for config.yaml:

# Example config.yaml
number:
  - platform: template
    name: Stepper Control
    min_value: -400
    max_value: 400
    step: 1
    set_action:
      then:
        - stepper.set_target:
            id: my_stepper
            target: !lambda 'return x;'

stepper:
  - platform: a4988
    id: my_stepper
    acceleration: 1000
    deceleration: 1000
    step_pin:
      number: D2
    dir_pin:
      number: D1
    sleep_pin:
      number: D3
    max_speed: 250 steps/s

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.