Add duty cycle output component (#894)

* Add duty cycle output component

* cleanup + tests

* format

* duty_cycle -> slow_pwm

* .

* clang-format

* ESP_LOGD -> ESPLOGVV

Co-Authored-By: Otto Winter <otto@otto-winter.com>

esphome/components/slow_pwm/slow_pwm_output.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/esphal.h"
+#include "esphome/components/output/float_output.h"
+
+namespace esphome {
+namespace slow_pwm {
+
+class SlowPWMOutput : public output::FloatOutput, public Component {
+ public:
+  void set_pin(GPIOPin *pin) { pin_ = pin; };
+  void set_period(unsigned int period) { period_ = period; };
+
+  /// Initialize pin
+  void setup() override;
+  void dump_config() override;
+  /// HARDWARE setup_priority
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
+
+ protected:
+  void write_state(float state) override;
+  void loop() override;
+
+  GPIOPin *pin_;
+  float state_{0};
+  unsigned int period_start_time_{0};
+  unsigned int period_{5000};
+};
+
+}  // namespace slow_pwm
+}  // namespace esphome