add some code

main/boards/common/backlight.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <cstdint>
+#include <functional>
+
+#include <driver/gpio.h>
+#include <esp_timer.h>
+
+
+class Backlight {
+public:
+    Backlight();
+    ~Backlight();
+
+    void RestoreBrightness();
+    void SetBrightness(uint8_t brightness, bool permanent = false);
+    inline uint8_t brightness() const { return brightness_; }
+
+protected:
+    void OnTransitionTimer();
+    virtual void SetBrightnessImpl(uint8_t brightness) = 0;
+
+    esp_timer_handle_t transition_timer_ = nullptr;
+    uint8_t brightness_ = 0;
+    uint8_t target_brightness_ = 0;
+    uint8_t step_ = 1;
+};
+
+
+class PwmBacklight : public Backlight {
+public:
+    PwmBacklight(gpio_num_t pin, bool output_invert = false, uint32_t freq_hz = 25000);
+    ~PwmBacklight();
+
+    void SetBrightnessImpl(uint8_t brightness) override;
+};