Update tca6408.h

components/TCA6408/tca6408.h

@@ -8,6 +8,16 @@
 namespace esphome {
 namespace tca6408 {
 
+/**
+ * TCA6408 8-bit I²C I/O Expander Component
+ *
+ * Features:
+ * - 8 bidirectional GPIO pins (0-7)
+ * - Hardware polarity inversion (for inputs)
+ * - Interrupt support (active-low open-drain INT pin)
+ * - Cached GPIO access for efficiency
+ * - Works with ESP32 (including C5), ESP8266, etc.
+ */
 class TCA6408Component : public Component,
                          public i2c::I2CDevice,
                          public gpio_expander::CachedGpioExpander<uint8_t, 8> {
@@ -17,26 +27,32 @@ class TCA6408Component : public Component,
   void dump_config() override;
   float get_setup_priority() const override { return setup_priority::IO; }
 
+  /** Set I²C address (default 0x20) */
   void set_address(uint8_t address) { this->address_ = address; }
+
+  /** Set ESP GPIO connected to TCA6408 INT pin (recommended) */
   void set_interrupt_pin(InternalGPIOPin *pin) { this->interrupt_pin_ = pin; }
 
+  /** Set hardware polarity inversion for a specific pin (used internally) */
   void set_polarity_inversion(uint8_t pin, bool inverted);
 
  protected:
+  /** Interrupt Service Routine - lightweight, runs in ISR context */
   static void IRAM_ATTR gpio_intr(TCA6408Component *arg);
 
+  // GPIO Expander overrides
   bool digital_read_hw(uint8_t pin) override;
   bool digital_read_cache(uint8_t pin) override;
   void digital_write_hw(uint8_t pin, bool value) override;
   void pin_mode(uint8_t pin, gpio::Flags flags) override;
 
-  uint8_t mode_mask_{0xFF};      // 1 = input, 0 = output
-  uint8_t output_mask_{0x00};
-  uint8_t input_mask_{0x00};
-  uint8_t polarity_mask_{0x00};  // 1 = inverted (hardware polarity for inputs)
+  uint8_t mode_mask_{0xFF};      // 1 = input, 0 = output (Config Register 0x03)
+  uint8_t output_mask_{0x00};    // Output Port Register 0x01
+  uint8_t input_mask_{0x00};     // Input Port Register 0x00
+  uint8_t polarity_mask_{0x00};  // Polarity Inversion Register 0x02 (1 = inverted)
 
-  InternalGPIOPin *interrupt_pin_{nullptr};
-  bool interrupt_triggered_{false};
+  InternalGPIOPin *interrupt_pin_{nullptr};  // ESP pin connected to TCA6408 INT
+  bool interrupt_triggered_{false};          // Flag set by ISR
 
  private:
   bool read_gpio_outputs_();