[esp] Add I2C LCD example.

esp/cpp/06_i2c-scanner/.gitignore

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+build
+managed_components
+dependencies.lock
+sdkconfig.old

esp/cpp/06_i2c-scanner/CMakeLists.txt

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+# For more information about build system see
+# https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/build-system.html
+# The following five lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.26)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+
+project(
+    #[[NAME]]   i2c-scanner
+    VERSION     0.1
+    DESCRIPTION "Simple I2C device scanner"
+    LANGUAGES   CXX
+)
+# For writing pure cmake components, see the documentation
+# https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-guides/build-system.html#writing-pure-cmake-components
+idf_build_set_property(COMPILE_OPTIONS "-Wno-error" APPEND)

esp/cpp/06_i2c-scanner/README.md

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+# 06_i2c-scanner
+
+![schematic](./schematic.png)
+
+Simple I2C device scanner.
+
+For this example I used this [SSD1306 OLED display](https://www.digikey.com/en/products/detail/winstar-display/WEA012864DWPP3N00003/20533255).
+
+To build the example run the following commands.
+
+```bash
+source ~/path/to/esp-idf/export.sh
+
+mkdir build
+cd build
+cmake ..
+make -j $(nproc)
+
+# Flash to ESP32
+make flash
+
+# Open Serial Monitor, press CTRL+] to exit.
+make monitor
+```
+
+Expected output in serial monitor at 115200 baud
+
+```bash
+Scanning I2C devices...
+[0x3c]: Device found with clock rate 100000 and timeout 50
+Done.
+```

esp/cpp/06_i2c-scanner/main/CMakeLists.txt

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+idf_component_register(
+    SRCS "main.cpp"
+    INCLUDE_DIRS "."
+)

esp/cpp/06_i2c-scanner/main/idf_component.yml

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+## IDF Component Manager Manifest File
+dependencies:
+  ## Required IDF version
+  idf:
+    version: '>=5.3.0'
+  # # Put list of dependencies here
+  # # For components maintained by Espressif:
+  # component: "~1.0.0"
+  # # For 3rd party components:
+  # username/component: ">=1.0.0,<2.0.0"
+  # username2/component2:
+  #   version: "~1.0.0"
+  #   # For transient dependencies `public` flag can be set.
+  #   # `public` flag doesn't have an effect dependencies of the `main` component.
+  #   # All dependencies of `main` are public by default.
+  #   public: true
+  espressif/arduino-esp32: ^3.1.1

esp/cpp/06_i2c-scanner/main/main.cpp

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+#include "Arduino.h"
+#include "Wire.h"
+
+[[maybe_unused]] static const char *TAG = "i2c-scanner";
+
+void i2c_scan()
+{
+  uint8_t device_num = 0;
+  Serial.println("Scanning I2C devices...");
+  for (byte address = 1; address < 127; address++) {
+    Wire.beginTransmission(address);
+    byte error = Wire.endTransmission();
+    if (error == 0) {
+      Serial.printf(
+          "[0x%.2x]: Device found with clock rate %lu and timeout %u\n",
+          address,
+          Wire.getClock(), Wire.getTimeOut());
+      device_num++;
+    } else if (error == 4) {
+      Serial.printf("[0x%.2x]: Unknown error.\n", address);
+    }
+  }
+  Serial.println(device_num > 0 ? "Done.\n" : "No I2C devices found.\n");
+}
+
+void setup()
+{
+  Serial.begin(115200);
+  Wire.begin();
+}
+
+void loop()
+{
+  i2c_scan();
+}

esp/cpp/07_lcd-panel-i2c/.gitignore

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+build
+managed_components
+dependencies.lock
+sdkconfig.old

esp/cpp/07_lcd-panel-i2c/CMakeLists.txt

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+# For more information about build system see
+# https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/build-system.html
+# The following five lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.26)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+
+project(
+    #[[NAME]]   lcd-panel-i2c
+    VERSION     0.1
+    DESCRIPTION "Using the SSD1306 LCD display with ESP-IDF and LVGL over I2C"
+    LANGUAGES   CXX
+)
+# For writing pure cmake components, see the documentation
+# https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-guides/build-system.html#writing-pure-cmake-components
+idf_build_set_property(COMPILE_OPTIONS "-Wno-error" APPEND)

esp/cpp/07_lcd-panel-i2c/README.md

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+# 07_lcd-panel-i2c
+
+Using the ESP IDF for drawing to a LCD screen over I2C.
+
+[ESP IDF - I2C](https://docs.espressif.com/projects/esp-idf/en/v5.3.2/esp32/api-reference/peripherals/i2c.html)
+
+[ESP IDF - LCD](https://docs.espressif.com/projects/esp-idf/en/v5.3.2/esp32/api-reference/peripherals/lcd/index.html)
+
+[ESP IDF - FreeRTOS](https://docs.espressif.com/projects/esp-idf/en/v5.3.2/esp32/api-reference/system/freertos.html)
+
+![schematic](./schematic.png)
+
+![example](./example.gif)
+
+For instructions on setting up the ESP-IDF see [04_-esp-idf-arduino](./../04_esp-idf-arduino)
+
+To build this example run the following commands.
+
+```bash
+source ~/path/to/esp-idf/export.sh
+
+mkdir build
+cd build
+cmake ..
+make -j $(nproc)
+make flash
+```

esp/cpp/07_lcd-panel-i2c/main/CMakeLists.txt

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+idf_component_register(
+    SRCS
+    main.cpp display.cpp panel_device.cpp scoped_lock.cpp
+    i2c.h time_keeper.h panel.h ssd1306.h
+    INCLUDE_DIRS .
+    REQUIRES driver
+)

esp/cpp/07_lcd-panel-i2c/main/display.cpp

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+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#include <lv_init.h>
+
+#include "display.h"
+
+// Static TimeKeeper for managing ESP timers across all displays.
+TimeKeeper Display::timers_;
+
+Display::Display(IPanelDevice &device) :
+    panel_(device)
+{
+  if (!lv_is_initialized()) {
+    ESP_LOGI(TAG, "Initialize LVGL");
+    lv_init();
+  }
+
+  ESP_LOGI(TAG, "Creating LVGL display");
+  lv_display_ = panel_.device_->create_display();
+  // associate the i2c panel handle to the display
+  lv_display_set_user_data(lv_display_, panel_.esp_panel_);
+
+  panel_.register_display_callbacks(lv_display_);
+}
+
+void Display::set_text(const char *text,
+                       const char *name,
+                       lv_label_long_mode_t long_mode,
+                       lv_align_t align)
+{
+  // Lock the mutex due to the LVGL APIs are not thread-safe.
+  ScopedLock lock;
+
+  ESP_LOGI(TAG, "Display LVGL Scroll Text");
+  lv_obj_t *scr = lv_display_get_screen_active(lv_display_);
+
+  // Create the label if it's `name` doesn't already exist in the map keys.
+  if (!lv_objects_.count(name)) {
+    lv_objects_[name] = lv_label_create(scr);
+  }
+  auto obj = lv_objects_[name];
+
+  // Set text and long mode.
+  lv_label_set_long_mode(obj, long_mode);
+  lv_label_set_text(obj, text);
+
+  // Set the size of the screen.
+  // If you use rotation 90 or 270 use lv_display_get_vertical_resolution.
+  lv_obj_set_width(obj, lv_display_get_horizontal_resolution(lv_display_));
+  lv_obj_align(obj, align, 0, 0);
+}

esp/cpp/07_lcd-panel-i2c/main/display.h

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+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#ifndef DISPLAY_H
+#define DISPLAY_H
+
+#include <widgets/label/lv_label.h>
+
+#include <unordered_map>
+
+#include "time_keeper.h"
+#include "panel.h"
+#include "scoped_lock.h"
+
+/**
+ * Encapsulates lv_display handle and related LVGL operations.
+ * Contains helper methods that wrap basic LVGL operations such as drawing text.
+ * The underlying lv_display can be obtained for manual LVGL operations.
+ * @sa ScopedLock
+ * @sa Display::get()
+ */
+class Display {
+public:
+  /**
+   * Construct a new Display using an object that implements IPanelDevice.
+   *
+   * @param device An object that implements the IPanelDevice interface.
+   */
+  explicit Display(IPanelDevice &device);
+
+  ~Display() = default;
+
+  Display(const Display &) = delete;
+
+  Display(Display &) = delete;
+
+  Display &operator=(Display &) = delete;
+
+  using lv_display_handle_t = lv_display_t *;
+
+  //
+  // GETTERS
+
+  /**
+   * Getter for accessing LVGL display handle.
+   *
+   * @sa ScopedLock for calling custom LVGL API's not implemented by Display.
+   */
+  [[nodiscard]] inline lv_display_handle_t get() const { return lv_display_; }
+
+  /**
+   * Getter for accessing LVGL display handle.
+   *
+   * @sa ScopedLock for calling custom LVGL API's not implemented by Display.
+   */
+  [[nodiscard]] inline lv_display_handle_t get() { return lv_display_; }
+
+  /// Dereference operator for accessing LVGL display handle.
+  [[nodiscard]] inline lv_display_handle_t operator*() const { return get(); }
+
+  /// Dereference operator for accessing LVGL display handle.
+  [[nodiscard]] inline lv_display_handle_t operator*() { return get(); }
+
+  //
+  // LVGL OPERATIONS
+
+  /**
+   * Create a LVGL label with some given text on the current display.
+   * The name of the object can be reused to change text on this label later.
+   *
+   * @param text Text to write to the display.
+   * @param name Name for the LVGL label object associated with this text.
+   * @param long_mode LVGL long mode for text wider than the current display.
+   * @param align LVGL alignment to use for placing the label on the display.
+   */
+  void set_text(const char *text,
+                const char *name,
+                lv_label_long_mode_t long_mode = LV_LABEL_LONG_SCROLL_CIRCULAR,
+                lv_align_t align = LV_ALIGN_TOP_MID);
+
+  //
+  // PUBLIC STATIC MEMBERS
+
+  /// Public static TimeKeeper for managing ESP timers across all displays.
+  static TimeKeeper timers_;
+
+private:
+
+  //
+  // PRIVATE MEMBERS
+
+  /// Panel associated with this Display.
+  Panel panel_;
+
+  /// LVGL display handle.
+  lv_display_handle_t lv_display_;
+
+  /**
+   * LVGL object handles stored in the LVGL screen associated with this Display.
+   *
+   * @sa Display::set_text
+   * @sa lv_display_get_screen_active
+   */
+  std::unordered_map<const char *, lv_obj_t *> lv_objects_;
+
+  /// Tag used for ESP logging.
+  constexpr static const char *TAG = "Display";
+};
+
+#endif // DISPLAY_H

esp/cpp/07_lcd-panel-i2c/main/i2c.h

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+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#ifndef I2C_H
+#define I2C_H
+
+#define I2C_BUS_PORT  0
+
+#include <driver/i2c_master.h>
+
+/**
+ * Encapsulates ESP I2C creation and usage.
+ */
+struct I2C {
+  /**
+   * Construct and initialize an ESP I2C master bus.
+   * An I2C constructor may only be called one time in any application.
+   *
+   * @param sda GPIO pin number for SDA
+   * @param scl GPIO pin number for SCL
+   * @param rst GPIO pin number for RST
+   */
+  I2C(gpio_num_t sda, gpio_num_t scl, int rst = -1) :
+      I2C((i2c_master_bus_config_t) {
+              .i2c_port = I2C_BUS_PORT,
+              .sda_io_num = sda,
+              .scl_io_num = scl,
+              .clk_source = I2C_CLK_SRC_DEFAULT,
+              .glitch_ignore_cnt = 7,
+              .flags {
+                  .enable_internal_pullup = true,
+              },
+          },
+          rst
+      ) { }
+
+  /**
+   * Construct an ESP I2C master bus given a specific ESP I2C configuration.
+   * An I2C constructor may only be called one time in any application.
+   *
+   * @param config ESP I2C master bus configuration.
+   * @param rst GPIO pin number for RST
+   */
+  explicit I2C(i2c_master_bus_config_t config, int rst = -1) :
+      esp_bus_config_(config),
+      rst_num_(rst)
+  {
+    i2c_master_bus_handle_t i2c;
+    ESP_LOGI(TAG, "Initializing new master I2C bus");
+    ESP_ERROR_CHECK(i2c_new_master_bus(&esp_bus_config_, &i2c));
+  }
+
+  ~I2C() = default;
+
+  //
+  // GETTERS
+
+  /**
+   * ESP I2C master bus handle getter.
+   * This will fail if an I2C instance was never constructed.
+   */
+  static i2c_master_bus_handle_t get()
+  {
+    i2c_master_bus_handle_t i2c = nullptr;
+    ESP_ERROR_CHECK(i2c_master_get_bus_handle(0, &i2c));
+    return i2c;
+  }
+
+  //
+  // PUBLIC MEMBERS
+
+  /// ESP I2C master bus configuration used during initialization.
+  i2c_master_bus_config_t esp_bus_config_;
+
+  /// RST GPIO pin number.
+  int rst_num_;
+
+private:
+
+  //
+  // PRIVATE MEMBERS
+
+  /// Tag used for ESP logging.
+  constexpr static const char *TAG = "I2C";
+};
+
+#endif //I2C_H

esp/cpp/07_lcd-panel-i2c/main/idf_component.yml

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+## IDF Component Manager Manifest File
+dependencies:
+  idf: '>=5.3.0'
+  espressif/arduino-esp32: ^3.1.1
+  lvgl/lvgl: "9.2.0"
+  esp_lcd_sh1107: "^1"

esp/cpp/07_lcd-panel-i2c/main/main.cpp

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+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#include "display.h"
+#include "ssd1306.h"
+
+// Pin may vary based on your schematic.
+#define PIN_SDA                GPIO_NUM_21
+#define PIN_SCL                GPIO_NUM_22
+#define PIN_RST                (-1)
+
+I2C i2c(PIN_SDA, PIN_SCL, PIN_RST);
+
+void setup()
+{
+  SSD1306 ssd1306(i2c);
+  Display d(ssd1306);
+
+  d.set_text("Test test 12345678910",
+             "test-text1",
+             LV_LABEL_LONG_SCROLL,
+             LV_ALIGN_CENTER);
+
+  d.set_text("Test test changing text",
+             "test-text1",
+             LV_LABEL_LONG_SCROLL,
+             LV_ALIGN_CENTER);
+
+  d.set_text("Hello hello hello hello hello hello hello hello!", "test-text2");
+
+  d.set_text("A random sentence with no meaning at all.",
+             "test-text3",
+             LV_LABEL_LONG_CLIP,
+             LV_ALIGN_BOTTOM_MID);
+}
+
+void loop() { }

esp/cpp/07_lcd-panel-i2c/main/panel.h

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+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#ifndef PANEL_H
+#define PANEL_H
+
+#include "panel_device.h"
+
+/**
+ * Encapsulates esp_lcd_panel handles and operations.
+ * The only exception is esp_lcd_panel_io_i2c_config_t owned by IPanelDevice.
+ * This structure requires details specific to the implementing device.
+ *
+ * Panel is an implementation detail of Display, not meant to be used directly.
+ */
+struct Panel {
+  /**
+   * Construct a new Panel using an object that implements IPanelDevice.
+   *
+   * @param device An object that implements the IPanelDevice interface.
+   */
+  explicit Panel(IPanelDevice &device) :
+      device_(&device),
+      esp_io_(nullptr),
+      esp_panel_(nullptr),
+      esp_panel_config_(
+          (esp_lcd_panel_dev_config_t) {
+              .reset_gpio_num = device_->rst_num_,
+              .bits_per_pixel = 1,
+              .vendor_config = device_->vendor_config(),
+          }
+      )
+  {
+    esp_io_ = device_->create_io_handle();
+
+    device_->create_panel(esp_panel_config_, esp_io_, esp_panel_);
+
+    ESP_LOGI(TAG, "Resetting panel display");
+    ESP_ERROR_CHECK(esp_lcd_panel_reset(esp_panel_));
+    ESP_LOGI(TAG, "Initializing panel display");
+    ESP_ERROR_CHECK(esp_lcd_panel_init(esp_panel_));
+    ESP_LOGI(TAG, "Turning on panel display");
+    ESP_ERROR_CHECK(esp_lcd_panel_disp_on_off(esp_panel_, true));
+  }
+
+  ~Panel() = default;
+
+  //
+  // PUBLIC MEMBERS
+
+  /// Pointer to object using known interface for IPanelDevice.
+  IPanelDevice *device_;
+
+  /// ESP LCD panel IO handle.
+  esp_lcd_panel_io_handle_t esp_io_;
+
+  /// ESP LCD panel handle.
+  esp_lcd_panel_handle_t esp_panel_;
+
+  /// ESP LCD panel configuration structure.
+  esp_lcd_panel_dev_config_t esp_panel_config_;
+
+  /**
+   * Registers LVGL draw buffers and callbacks for rendering the display.
+   *
+   * @param display_handle Pointer to the LVGL display to use for rendering.
+   */
+  inline void register_display_callbacks(lv_display_t *display_handle) const
+  {
+    device_->register_rendering_data(display_handle, esp_io_);
+    device_->register_lvgl_tick_timer();
+  }
+
+private:
+
+  //
+  // PRIVATE MEMBERS
+
+  /// Tag used for ESP logging.
+  constexpr static const char *TAG = "Panel";
+};
+
+#endif //PANEL_H

esp/cpp/07_lcd-panel-i2c/main/panel_device.cpp

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+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#include "panel_device.h"
+#include "display.h"
+
+bool IPanelDevice::lvgl_flush_ready_cb(esp_lcd_panel_io_handle_t,
+                                       esp_lcd_panel_io_event_data_t *,
+                                       void *user_ctx)
+{
+  auto *disp = (lv_display_t *) user_ctx;
+  lv_display_flush_ready(disp);
+  return false;
+}
+
+void IPanelDevice::lvgl_flush_cb(lv_display_t *display, const lv_area_t *area,
+                                 uint8_t *px_map) // NOLINT(*-non-const-parameter)
+{
+  auto panel_handle =
+      (esp_lcd_panel_handle_t) lv_display_get_user_data(display);
+
+  // Necessary because LVGL reserves 2x4 bytes in the buffer for a palette.
+  // Since we are monochrome, we don't need these additional bytes.
+  // For more information about the monochrome, please refer to:
+  // https://docs.lvgl.io/9.2/porting/display.html#monochrome-displays
+  // Skip the palette here.
+  px_map += LVGL_PALETTE_SIZE;
+
+  uint16_t hor_res = lv_display_get_physical_horizontal_resolution(display);
+  int32_t x1 = area->x1;
+  int32_t x2 = area->x2;
+  int32_t y1 = area->y1;
+  int32_t y2 = area->y2;
+
+
+  // As of 03/01/2025 master branch of LVGL contains this helper for the same.
+  // https://docs.lvgl.io/master/API/draw/sw/lv_draw_sw_utils.html
+  // lv_draw_sw_i1_convert_to_vtiled()
+  for (int32_t y = y1; y <= y2; y++) {
+    for (int32_t x = x1; x <= x2; x++) {
+      // Get the byte offset of the pixel coordinates using horizontal-mapping.
+      int h_offset = Pixel::horizontal_byte_offset(x, y, hor_res);
+      // True if the pixel is lit, else false.
+      bool chroma_color = px_map[h_offset] & Pixel::msb_mask(x);
+
+      // We need an additional buffer for transposing the pixel data to the
+      // vertical format required by the display driver.
+      uint8_t *buf = IPanelDevice::get_additional_draw_buffer();
+      // Move to the position in the auxillary buffer where the pixel is stored.
+      buf += Pixel::vertical_byte_offset(x, y, hor_res);
+
+      // Write the single bit to the monochrome display mapped vertically.
+      // Take the Least Significant Bit mask of the Y coordinate to select the
+      // bit representing a pixel at position y in a vertically-mapped display.
+      if (chroma_color) {
+        // Set the vertically-mapped pixel to on.
+        *buf &= ~Pixel::lsb_mask(y);
+      } else {
+        // Set the vertically-mapped pixel to off.
+        *buf |= Pixel::lsb_mask(y);
+      }
+    }
+  }
+  // Pass the draw buffer to the driver.
+  ESP_ERROR_CHECK(
+      esp_lcd_panel_draw_bitmap(panel_handle, x1, y1, x2 + 1, y2 + 1,
+                                IPanelDevice::get_additional_draw_buffer()));
+}
+
+void IPanelDevice::lvgl_increase_tick_cb(void *)
+{
+  // Tell LVGL how many milliseconds has elapsed
+  lv_tick_inc(LVGL_TICK_PERIOD_MS);
+}
+
+[[noreturn]] void IPanelDevice::lvgl_port_task(void *)
+{
+  // Optionally initialize some LVGL objects here before entering loop below.
+
+  ESP_LOGI(TAG, "Starting LVGL task");
+  for (uint32_t time_to_next_ms = 0; true; usleep(1000 * time_to_next_ms)) {
+    // Obtain LVGL API lock before calling any LVGL methods.
+    ScopedLock lock;
+
+    // Optionally handle LVGL input or event logic here.
+
+    // Update LVGL periodic timers.
+    time_to_next_ms = lv_timer_handler();
+  }
+}
+
+void IPanelDevice::register_rendering_data(lv_display_t *display_handle,
+                                           esp_lcd_panel_io_handle_t io_handle)
+{
+  // Create draw buffer.
+  ESP_LOGI(TAG, "Allocate separate LVGL draw buffers");
+  lv_buf_ = heap_caps_calloc(1, lv_buf_size_,
+                             MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT);
+  assert(lv_buf_);
+
+  ESP_LOGI(TAG, "Set LVGL draw buffers");
+  // Color format must be set first, LVGL9 suooprt new monochromatic format.
+  lv_display_set_color_format(display_handle, LV_COLOR_FORMAT_I1);
+  lv_display_set_buffers(display_handle, lv_buf_, nullptr,
+                         lv_buf_size_,
+                         LV_DISPLAY_RENDER_MODE_FULL);
+  lv_display_set_rotation(display_handle, LV_DISPLAY_ROTATION_0);
+
+  ESP_LOGI(TAG, "Set LVGL callback for flushing to the display");
+  lv_display_set_flush_cb(display_handle, IPanelDevice::lvgl_flush_cb);
+
+  ESP_LOGI(TAG, "Register io panel callback for LVGL flush ready notification");
+  const esp_lcd_panel_io_callbacks_t cbs = {
+      .on_color_trans_done = IPanelDevice::lvgl_flush_ready_cb,
+  };
+  ESP_ERROR_CHECK(
+      esp_lcd_panel_io_register_event_callbacks(io_handle, &cbs,
+                                                display_handle));
+}
+
+void IPanelDevice::register_lvgl_tick_timer()
+{
+  ESP_LOGI(TAG, "Use esp_timer to increase LVGL tick");
+  const esp_timer_create_args_t esp_timer_args = {
+      .callback = &IPanelDevice::lvgl_increase_tick_cb,
+      // Data to pass to the IPanelDevice::lvgl_port_task callback.
+      .arg = nullptr,
+      .name = "lvgl_tick",
+  };
+  Display::timers_.start_new_timer_periodic(esp_timer_args,
+                                            LVGL_TICK_PERIOD_MS * 1000);
+
+  // LVGL requires a FreeRTOS task for running it's event loop.
+  // The lvgl_port_task callback can update the UI or handle input logic.
+  // For this basic example we don't do either of these things.
+  ESP_LOGI(TAG, "Create LVGL FreeRTOS task");
+  // Optionally set user data to pass to LVGL's FreeRTOS task callback here.
+  void *user_data = nullptr;
+  xTaskCreate(lvgl_port_task, "LVGL", LVGL_TASK_STACK_SIZE,
+              user_data, LVGL_TASK_PRIORITY, nullptr);
+}

esp/cpp/07_lcd-panel-i2c/main/panel_device.h

@@ -0,0 +1,435 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#ifndef PANEL_DEVICE_H
+#define PANEL_DEVICE_H
+
+#include <esp_lcd_panel_dev.h>
+#include <esp_lcd_panel_ops.h>
+#include <esp_lcd_panel_io.h>
+#include <esp_log.h>
+
+#include <display/lv_display.h>
+
+#include "i2c.h"
+
+// LVGL reserves 2x4 bytes in the buffer to be used as a palette.
+// This additional space must be added to the IPanelDevice::buf_size_.
+#define LVGL_PALETTE_SIZE      8
+#define LVGL_TICK_PERIOD_MS    5
+#define LVGL_TASK_STACK_SIZE   (4 * 1024)
+#define LVGL_TASK_PRIORITY     2
+
+#define LCD_H_RES              128
+#define LCD_V_RES              64
+
+/**
+ * Wraps some foundational operations performed on pixel coordinates when
+ * dealing with pointer arithmetic. Most of these could be done ad-hoc as needed
+ * but using this helper reduces the risk of errors.
+ */
+struct Pixel {
+  /**
+   * Calculate byte offset for the pixel at [x,y] within a horizontally-mapped
+   * monochrome uint8 draw buffer, using the initialized horizontal resolution.
+   *
+   * We use `>> 3` because each pixel requires 1 bit, but each uint8 in the draw
+   * buffer can hold 8 bits. To find the uint8 value in our draw buffer that
+   * stores this pixel's value we must compensate for this when using pixel
+   * coordinates in byte math.
+   *
+   * Therefore, each uint8 in the draw buffer stores the state of 8 pixels.
+   * Below is an example of calculating for [x, y] pixel coordinates [20, 10].
+   * The example uses a horizontal resolution of 128.
+   *
+   * For the horizontal case, each row (y) of the image is represented by
+   * `hor_res >> 3` bytes (16). The byte-offset of the first pixel in the 10th
+   * row for example is `16 * 10` = 160.
+   *
+   * Since the pixels are stored horizontally we must calculate the 20th pixel
+   * column (x) as `160 + (20 >> 3)`, or `160 + (20 / 8)` to get a final offset
+   * of 162.
+   *
+   * @param x X pixel coordinate to find byte offset.
+   * @param y Y pixel coordinate to find byte offset.
+   * @param hor_res horizontal resolution of the display.
+   * @return byte offset for a single-byte monochrome pixel at [x,y].
+   */
+  [[maybe_unused]] [[nodiscard]] static ptrdiff_t
+  horizontal_byte_offset(const int32_t &x, const int32_t &y,
+                         const int32_t &hor_res = LCD_V_RES)
+  {
+    // Convert pixel (bit) coordinates to byte coordinates in the draw buffer.
+    return (hor_res >> 3) * y + (x >> 3);
+  }
+
+  /**
+   * Calculate byte offset for the pixel at [x,y] within a vertically-mapped
+   * monochrome uint8 draw buffer, using the initialized horizontal resolution.
+   *
+   * We use `>> 3` because each pixel requires 1 bit, but each uint8 in the draw
+   * buffer can hold 8 bits. To find the uint8 value in our draw buffer that
+   * stores this pixel's value we must compensate for this when using pixel
+   * coordinates in byte math.
+   *
+   * Therefore, each uint8 in the draw buffer stores the state of 8 pixels.
+   * Below is an example of calculating for [x, y] pixel coordinates [20, 10].
+   * The example uses a horizontal resolution of 128.
+   *
+   * For the vertical case, each row (y) of the image is represented by
+   * `hor_res` bytes (128) - one for each column (x). Because the pixels are
+   * stored vertically, the byte-offset of the first pixel in the 10th row is
+   * `128 * (10 >> 3)` or * `128 * (10 / 8)` = 128.
+   *
+   * From this location we can simply calculate the 20th pixel column (x) as
+   * `128 + 20` to get a final offset of 148, because the pixels are stored in a
+   * columnar format.
+   *
+   * @param x X pixel coordinate to find byte offset.
+   * @param y Y pixel coordinate to find byte offset.
+   * @param hor_res horizontal resolution of the display.
+   * @return byte offset for a single-byte monochrome pixel at [x,y].
+   */
+  [[maybe_unused]] [[nodiscard]] static ptrdiff_t
+  vertical_byte_offset(const int32_t &x, const int32_t &y,
+                       const int32_t &hor_res = LCD_V_RES)
+  {
+    // Convert pixel (bit) coordinates to byte coordinates in the draw buffer.
+    return hor_res * (y >> 3) + x;
+  }
+
+  /**
+   * Finds the Most Significant Bit location of bit `i` in a byte.
+   *
+   *          MSB           LSB
+   * bits      7 6 5 4 3 2 1 0
+   * data      8 7 6 5 4 3 2 1
+   *          Left         Right
+   *
+   * @return bitmask for MSB location of `i`.
+   */
+  [[maybe_unused]] [[nodiscard]] static uint8_t
+  msb_mask(const int32_t &i) { return 1 << (7 - i % 8); }
+
+  /**
+   * Finds the Least Significant Bit location of bit `i` in a byte.
+   *
+   *          LSB           MSB
+   * bits      0 1 2 3 4 5 6 7
+   * data      1 2 3 4 5 6 7 8
+   *          Left         Right
+   *
+   * @return bitmask for LSB location of `i`.
+   */
+  [[maybe_unused]] [[nodiscard]] static uint8_t
+  lsb_mask(const int32_t &i) { return 1 << (i % 8); }
+};
+
+
+/**
+ * Encapsulates vendor specific ESP LCD panel initialization logic.
+ * This pure virtual interface can be inherited from for using new LCD devices.
+ * See SSD1306 as an example to implement IPanelDevice for NT35510 or ST7789.
+ *
+ * At this time only I2C is supported.
+ * Classes that inherit from this interface should likely be marked final.
+ */
+class IPanelDevice {
+public:
+  /**
+   * Construct an IPanelDevice.
+   *
+   * @param i2c I2C object. Eventually this will mature to IProtocol or similar.
+   * @param config I2C configuration for this device.
+   * @param height Height of the device screen in pixels.
+   * @param width Width of the device screen in pixels.
+   */
+  explicit IPanelDevice(I2C &i2c,
+                        esp_lcd_panel_io_i2c_config_t config,
+                        int width,
+                        int height) :
+      IPanelDevice(i2c, config, width, height,
+                   width * height / 8 + LVGL_PALETTE_SIZE) { }
+
+  /**
+   * Construct an IPanelDevice.
+   *
+   * @param i2c I2C object. Eventually this will mature to IProtocol or similar.
+   * @param config I2C configuration for this device.
+   * @param height Height of the device screen in pixels.
+   * @param width Width of the device screen in pixels.
+   * @param draw_buf_size Size of the draw buffer for this device.
+   */
+  explicit IPanelDevice(I2C &i2c,
+                        esp_lcd_panel_io_i2c_config_t io_config,
+                        int width,
+                        int height,
+                        size_t draw_buf_size) :
+      width_(width),
+      height_(height),
+      rst_num_(i2c.rst_num_),
+      lv_buf_size_(draw_buf_size),
+      esp_io_config_(io_config),
+      lv_buf_(nullptr) { }
+
+  virtual ~IPanelDevice() = default;
+
+  //
+  // PUBLIC METHODS
+
+  /**
+   * Create an LVGL display using the width and height of this device.
+   *
+   * @return Handle to the created LVGL display.
+   */
+  [[nodiscard]] lv_display_t *create_display() const
+  {
+    auto display = lv_display_create(width_, height_);
+    assert(display);
+    return display;
+  }
+
+  /**
+   * Create an ESP LCD panel IO handle.
+   *
+   * @return The created ESP LCD panel IO handle.
+   */
+  [[nodiscard]] esp_lcd_panel_io_handle_t create_io_handle()
+  {
+    ESP_LOGI(TAG, "Creating panel IO handle");
+    esp_lcd_panel_io_handle_t handle = nullptr;
+    ESP_ERROR_CHECK(
+        esp_lcd_new_panel_io_i2c(I2C::get(), &esp_io_config_, &handle));
+    return handle;
+  }
+
+  /**
+   * Create and initialize an ESP panel handle.
+   * IPanelDevice implementors must initialize the panel within init_panel.
+   *
+   * @param config ESP LCD panel configuration.
+   * @param io ESP LCD panel IO handle.
+   * @param [out] panel ESP LCD panel handle output pointer location.
+   */
+  void create_panel(esp_lcd_panel_dev_config_t &config,
+                    esp_lcd_panel_io_handle_t io,
+                    esp_lcd_panel_handle_t &panel)
+  {
+    // If the passed handle is already allocated, delete it.
+    if (panel != nullptr) {
+      ESP_LOGI(TAG, "Removing unused panel");
+      esp_lcd_panel_del(panel);
+    }
+
+    ESP_LOGI(TAG, "Installing vendor panel driver");
+    // Call pure virtual method responsible for initializing the panel handle.
+    init_panel(config, io, panel);
+  }
+
+  /**
+   * Retrieve the device specific vendor configuration structure.
+   *
+   * @return Address of vendor configuration structure.
+   * @sa SSD1306::vendor_config
+   */
+  virtual void *vendor_config() = 0;
+
+  /**
+   * Registers LVGL draw buffers and callbacks for this display.
+   *
+   * An implementation of the interface can optionally override this method to
+   * provide custom LVGL callbacks and display configurations.
+   *
+   * @param display_handle LVGL display handle to use for rendering.
+   * @param io_handle IO handle for the ESP LCD panel.
+   */
+  virtual void register_rendering_data(lv_display_t *display_handle,
+                                       esp_lcd_panel_io_handle_t io_handle);
+
+  /**
+   * Registers LVGL ticker timer callback for rendering this display.
+   *
+   * An implementation of the interface can optionally override this method to
+   * provide custom LVGL callbacks and tick configurations.
+   */
+  virtual void register_lvgl_tick_timer();
+
+  //
+  // PUBLIC MEMBERS
+
+  /// Width of the device screen in pixels.
+  int32_t width_;
+
+  /// Height of the device screen in pixels.
+  int32_t height_;
+
+  /// RST GPIO pin number.
+  int rst_num_;
+
+  /// LVGL draw buffer size for the device.
+  size_t lv_buf_size_;
+
+  /// ESP LCD panel IO configuration.
+  esp_lcd_panel_io_i2c_config_t esp_io_config_;
+
+protected:
+  /**
+   * Static accessor to a static buffer to store draw buffer data for the panel.
+   *
+   * This method is protected to allow an implementation to provide a custom
+   * callback method similar to IPanelDevice::lvgl_flush_cb.
+   *
+   * The buffer is allocated statically within the scope of this function to
+   * allow creating multiple panels that _each_ manage their own statically
+   * allocated draw buffer data. This simplifies implementing the interface by
+   * taking this responsibility off of the implementor. The buffer will only be
+   * allocated if this method is called, so the memory is only used if required.
+   *
+   * @return Pointer to uint8 draw buffer data.
+   * @sa register_rendering_data for overriding LVGL rendering callbacks.
+   */
+  static uint8_t *get_additional_draw_buffer()
+  {
+    // Static to the scope of this function, not the compilation unit.
+    // For LV_COLOR_FORMAT_I1 we need an extra buffer to hold converted data.
+    static uint8_t oled_buffer[LCD_H_RES * LCD_V_RES / 8];
+    return oled_buffer;
+  }
+
+private:
+
+  //
+  // PRIVATE METHODS
+
+  /**
+    * Initializes the ESP panel using vendor specific APIs and configurations.
+    * This method should implement any setup logic specific to the device.
+    *
+    * @param config ESP LCD panel configuration.
+    * @param io ESP LCD panel IO handle.
+    * @param [out] panel ESP LCD panel handle output pointer location.
+    */
+  virtual void init_panel(esp_lcd_panel_dev_config_t &config,
+                          esp_lcd_panel_io_handle_t io,
+                          esp_lcd_panel_handle_t &panel) = 0;
+
+  //
+  // PRIVATE STATIC METHODS
+
+/**
+ * The callback invoked when panel IO finishes transferring color data.
+ * This signals that the panel is ready to flush image data to the display.
+ *
+ * @param panel LCD panel IO handles.
+ * @param data Panel IO event data, fed by driver.
+ * @param user_ctx User data, passed from `esp_lcd_panel_io_xxx_config_t`.
+ * @return Whether a high priority task has been waken up by this function.
+ * @sa SSD1306::SSD1306 for setting user_ctx data passed to the callback.
+ * @sa register_rendering_data for overriding this callback.
+ */
+  static bool lvgl_flush_ready_cb(esp_lcd_panel_io_handle_t panel,
+                                  esp_lcd_panel_io_event_data_t *data,
+                                  void *user_ctx);
+
+  /**
+   * The callback invoked for flushing the rendered image to the display.
+   *
+   * `px_map` contains the rendered image as raw pixel map and it should be
+   *  copied to `area` on the display.
+   *
+   * The following details are crucial for understanding the logic surrounding
+   * flushing to the display in this example.
+   *
+   * The order of bits within the px_map from _LVGL_ is MSB first.
+   *              MSB           LSB
+   *     bits      7 6 5 4 3 2 1 0
+   *     pixels    0 1 2 3 4 5 6 7
+   *              Left         Right
+   *
+   * The bytes from _LVGL_ are mapped to pixel rows of the display
+   * 8 bits (pixels) per byte -
+   * [0, 0, 0, 0, 0, 0, 0, 0]
+   * [0, 0, 0, 0, 0, 0, 0, 0]
+   * [0, 0, 0, 0, 0, 0, 0, 0]
+   *
+   * The order of bits expected by the _display driver_ is LSB first.
+   * We must preserve pairing of each bit and pixel when writing to the display.
+   *              LSB           MSB
+   *     bits      0 1 2 3 4 5 6 7
+   *     pixels    7 6 5 4 3 2 1 0
+   *              Left         Right
+   *
+   * Bytes expected by the _display driver_ map to pixel columns of the display.
+   * 8 bits (pixels) per byte -
+   * [0, [0, [0, [0,
+   *  0,  0,  0,  0,
+   *  0,  0,  0,  0,
+   *  0,  0,  0,  0,
+   *  0,  0,  0,  0,
+   *  0,  0,  0,  0,
+   *  0,  0,  0,  0,
+   *  0]  0]  0]  0]
+   *
+   * These layouts in memory have no opinion on the shape of the image. The
+   * beginning and end of a row or a column for example is entirely dependent
+   * on how the data is accessed. The vertical and horitzontal resolution may
+   * vary between displays.
+   *
+   * For the LV_COLOR_FORMAT_I1 color format we are using, an additional buffer
+   * is needed for transposing the bits to the vertical arrangement required by
+   * the display driver that is outlined above.
+   *
+   * This callback implementation is an example of handling this transposition
+   * and flushing the data to the display in the expected format.
+   *
+   * @param display LVGL display handle to use for rendering.
+   * @param area Area of the display being flushed.
+   * @param px_map Rendered image data for writing to the display area.
+   * @sa register_rendering_data for overriding this callback.
+   * @sa get_additional_draw_buffer
+   */
+  static void lvgl_flush_cb(lv_display_t *display,
+                            const lv_area_t *area,
+                            uint8_t *px_map);
+
+  /**
+   * Callback invoked for every period of the timer.
+   *
+   * This callback _must_ call lv_tick_inc to inform LVGL how much time has
+   * elapsed since the last period of the timer.
+   *
+   * @param data User data passed to the callback.
+   * @sa register_lvgl_tick_timer for setting user data and the tick period of
+   *        the timer, or overriding this callback entirely.
+   */
+  static void lvgl_increase_tick_cb(void *data);
+
+  /**
+   * FreeRTOS task callback invoked for handling LVGL events or updating the UI.
+   *
+   * This function is intentionally an endless loop and should never return.
+   * LVGL initialization logic can optionally be added before entering the loop.
+   * Input logic can optionally be handled within the loop.
+   *
+   * This callback _must_ call lv_timer_handler to handle LVGL periodic timers.
+   *
+   * @param data User data passed to the callback.
+   * @sa register_lvgl_tick_timer for overriding this callback.
+   */
+  [[noreturn]] static void lvgl_port_task(void *data);
+
+  //
+  // PRIVATE MEMBERS
+
+  /// LVGL draw buffer associated with this Display's lv_display_t.
+  void *lv_buf_;
+
+  /// Tag used for ESP logging.
+  constexpr static const char *TAG = "IPanelDevice";
+};
+
+#endif // PANEL_DEVICE_H

esp/cpp/07_lcd-panel-i2c/main/scoped_lock.cpp

@@ -0,0 +1,12 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#include "scoped_lock.h"
+
+// LVGL library is not thread-safe, this example calls LVGL APIs from tasks.
+// We must use a mutex to protect it.
+_lock_t ScopedLock::lv_lock_;

esp/cpp/07_lcd-panel-i2c/main/scoped_lock.h

@@ -0,0 +1,28 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#ifndef SCOPED_LOCK_H
+#define SCOPED_LOCK_H
+
+#include <mutex>
+
+/**
+ * Obtains LVGL API mutex lock for the duration of local scope.
+ *
+ * LVGL library is not thread-safe, this lock should be held when making calls
+ * to the LVGL API, and released as soon as possible when finished.
+ */
+struct ScopedLock {
+  explicit ScopedLock() { _lock_acquire(&lv_lock_); }
+
+  ~ScopedLock() { _lock_release(&lv_lock_); }
+
+  /// Mutex used to protect LVGL API calls.
+  static _lock_t lv_lock_;
+};
+
+#endif // SCOPED_LOCK_H

esp/cpp/07_lcd-panel-i2c/main/ssd1306.h

@@ -0,0 +1,106 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#ifndef SSD1306_H
+#define SSD1306_H
+
+#include <esp_lcd_panel_ssd1306.h>
+
+#include "panel_device.h"
+
+// According to specific display hardware.
+// https://www.digikey.com/en/products/detail/winstar-display/WEA012864DWPP3N00003/20533255
+#define SCREEN_WIDTH           128  // OLED display width, in pixels.
+#define SCREEN_HEIGHT          64  // OLED display height, in pixels.
+
+// According to SSD1306 datasheet.
+// https://cdn-shop.adafruit.com/datasheets/SSD1306.pdf
+#define I2C_HW_ADDR            0x3C
+#define LCD_PIXEL_CLOCK_HZ     (400 * 1000)
+// Bit number used to represent command and parameter
+#define LCD_CMD_BITS           8
+#define LCD_PARAM_BITS         8
+
+/**
+ * Example of implementing the IPanelDevice interface for SSD1306 LCD device.
+ */
+class SSD1306 final : public IPanelDevice {
+public:
+  /**
+   * Construct a new SSD1306 device.
+   *
+   * @param i2c I2C master bus to manage this device.
+   */
+  explicit SSD1306(I2C &i2c) :
+      SSD1306(i2c, {.height = SCREEN_HEIGHT}) { }
+
+  /**
+   * Construct a new SSD1306 device given a specific SSD1306 configuration.
+   *
+   * @param i2c I2C master bus to manage this device.
+   * @param config SSD1306 vendor configuration.
+   * @param width Width of the device screen in pixels.
+   * @param height Height of the device screen in pixels.
+   */
+  SSD1306(I2C &i2c,
+          esp_lcd_panel_ssd1306_config_t config,
+          int width = SCREEN_WIDTH,
+          int height = SCREEN_HEIGHT
+  ) :
+      IPanelDevice(i2c,
+                   (esp_lcd_panel_io_i2c_config_t) {
+                       .dev_addr = I2C_HW_ADDR,
+                       // User data to pass to the LVGL flush_ready callback.
+                       // See IPanelDevice::lvgl_flush_ready_cb
+                       .user_ctx = nullptr,
+                       .control_phase_bytes = 1,
+                       .dc_bit_offset = 6,
+                       .lcd_cmd_bits = LCD_CMD_BITS,
+                       .lcd_param_bits = LCD_PARAM_BITS,
+                       .scl_speed_hz = LCD_PIXEL_CLOCK_HZ,
+                   },
+                   width,
+                   height
+      ),
+      ssd1306_config_(config) { }
+
+  ~SSD1306() final = default;
+
+  //
+  // PUBLIC METHODS
+
+  /**
+   * Provides the SSD1306 vendor configuration to IPanelDevice consumers.
+   *
+   * @return Address of the SSD1306 vendor configuration structure.
+   */
+  void *vendor_config() override
+  {
+    return &ssd1306_config_;
+  }
+
+  //
+  // PUBLIC MEMBERS
+
+  /// SSD1306 configuration structure.
+  esp_lcd_panel_ssd1306_config_t ssd1306_config_;
+
+private:
+
+  //
+  // PRIVATE METHODS
+
+  /// Initializes the ESP LCD panel handle for the SSD1306 device.
+  void init_panel(esp_lcd_panel_dev_config_t &config,
+                  esp_lcd_panel_io_handle_t io,
+                  esp_lcd_panel_handle_t &panel) override
+  {
+    ESP_ERROR_CHECK(esp_lcd_new_panel_ssd1306(io, &config, &panel));
+  }
+};
+
+#endif // SSD1306_H

esp/cpp/07_lcd-panel-i2c/main/time_keeper.h

@@ -0,0 +1,161 @@
+/*#############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2025 Shaun Reed, all rights reserved               ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com                     ##
+##############################################################################
+*/
+#ifndef TIME_KEEPER_H
+#define TIME_KEEPER_H
+
+#include <esp_log.h>
+#include <esp_timer.h>
+
+#include "i2c.h"
+
+/**
+ * Stores arguments and ESP timer handle for a Timer.
+ * In general Timers should be used via the TimeKeeper interface only.
+ *
+ * Timers cannot be copied, and are only created by a TimeKeeper instance.
+ * The TimeKeeper can delete existing Timers, calling it's destructor.
+ * The ESP timer will be deleted when this class desctructor is called.
+ */
+struct Timer {
+  explicit Timer(esp_timer_create_args_t args) :
+      args_(args), esp_timer_(nullptr)
+  {
+    ESP_LOGI(TAG, "Creating esp_timer with name: '%s'", args_.name);
+    ESP_ERROR_CHECK(esp_timer_create(&args, &esp_timer_));
+  }
+
+  ~Timer()
+  {
+    ESP_LOGI(TAG, "Destroying esp_timer with name: '%s'", args_.name);
+    ESP_ERROR_CHECK(esp_timer_delete(esp_timer_));
+  }
+
+  Timer(const Timer &) = delete;
+
+  Timer(Timer &) = delete;
+
+  Timer &operator=(Timer &) = delete;
+
+  //
+  // PUBLIC MEMBERS
+
+  /// Arguments passed to ESP API during timer creation.
+  esp_timer_create_args_t args_;
+
+  /// ESP timer handle.
+  esp_timer_handle_t esp_timer_;
+
+private:
+
+  //
+  // PRIVATE MEMBERS
+
+  /// Tag used for ESP logging.
+  constexpr static const char *TAG = "Timer";
+};
+
+/**
+ * ESP timer mananger class.
+ *
+ * Timers should only be accessed using the get_handle method.
+ * If the Timer destructor is called the underlying ESP timer will be deleted.
+ */
+struct TimeKeeper {
+  /// Timer handle type used for referring to Timers.
+  using TimerHandle = Timer *;
+
+  //
+  // GETTERS
+
+  TimerHandle get_handle(const char *name)
+  {
+    return &managed_timers_.at(name);
+  }
+
+  TimerHandle operator[](const char *name) { return get_handle(name); }
+
+  //
+  // PUBLIC METHODS
+
+  /**
+   * Create a new managed Timer with the provided ESP arguments.
+   * The timer can be retrieved later using the args.name field value.
+   *
+   * @param args ESP timer creation arguments.
+   * @return TimerHandle Handle to a Timer managed by this TimeKeeper.
+   * @sa get_handle
+   * @sa operator[](const char*)
+   */
+  [[maybe_unused]] TimerHandle create_timer(esp_timer_create_args_t args)
+  {
+    auto rt = managed_timers_.emplace(args.name, args);
+    if (!rt.second) {
+      ESP_LOGE(TAG, "Timer already exists with name '%s'", args.name);
+      return nullptr;
+    }
+    return &rt.first->second;
+  }
+
+  /// Stop a Timer with the given name.
+  [[maybe_unused]] void stop_timer(const char *name)
+  {
+    ESP_ERROR_CHECK(esp_timer_stop(get_handle(name)->esp_timer_));
+  }
+
+  /// Delete a Timer with the given name.
+  [[maybe_unused]] void delete_timer(const char *name)
+  {
+    if (managed_timers_.erase(name) == 0) {
+      ESP_LOGE(TAG, "Attempt to delete timer that does not exist: '%s'", name);
+    }
+  }
+
+  /// Create a Timer with the ESP args and call esp_timer_start_periodic.
+  [[maybe_unused]] void
+  start_new_timer_periodic(esp_timer_create_args_t args,
+                           uint64_t period)
+  {
+    start_timer_periodic(create_timer(args)->args_.name, period);
+  }
+
+  /// Calls esp_timer_start_periodic on the Timer with the given name.
+  [[maybe_unused]] void start_timer_periodic(const char *name,
+                                             uint64_t period)
+  {
+    ESP_ERROR_CHECK(
+        esp_timer_start_periodic(get_handle(name)->esp_timer_, period));
+  }
+
+  /// Create a Timer with the ESP args and call esp_timer_start_once.
+  [[maybe_unused]] void start_new_timer_once(esp_timer_create_args_t args,
+                                             uint64_t timeout_us)
+  {
+    start_timer_once(create_timer(args)->args_.name, timeout_us);
+  }
+
+  /// Calls esp_timer_start_once on the Timer with the given name.
+  [[maybe_unused]] void start_timer_once(const char *name,
+                                         uint64_t timeout_us)
+  {
+    ESP_ERROR_CHECK(
+        esp_timer_start_once(get_handle(name)->esp_timer_, timeout_us));
+  }
+
+private:
+
+  //
+  // PRIVATE MEMBERS
+
+  /// Existing ESP timers created for this TimeKeeper instance.
+  std::unordered_map<const char *, Timer> managed_timers_;
+
+  /// Tag used for ESP logging.
+  constexpr static const char *TAG = "TimeKeeper";
+};
+
+#endif // TIME_KEEPER_H

esp/cpp/README.md

@@ -7,6 +7,8 @@ shaunrd0/klips/esp/
 ├── 03_temp-humidity-web        # Temperature and humidity sensor within a web browser.
 ├── 04_esp-idf-arduino          # CMake example instead of Arduino IDE for ESP development.
 ├── 05_temp-humidity-web        # Temperature and humidity sensor within a web browser.
+├── 06_i2c-scanner              # Simple I2C device scanner.
+├── 07_lcd-panel-i2c            # Drawing to a LCD display with LVGL over I2C.
 ├── ESP32-basic-starter-kit.pdf # PDF for tutorials in ESP32 starter kit.
 ├── ESP32-dev-module.png
 └── README.md