Fix ESP logging tags.

+ Refactor most classes to header only.

esp/cpp/06_i2c-scanner/.gitignore

@@ -0,0 +1,4 @@
+build
+managed_components
+dependencies.lock
+sdkconfig.old

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

@@ -0,0 +1,17 @@
+# 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

@@ -0,0 +1,32 @@
+# 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

@@ -0,0 +1,4 @@
+idf_component_register(
+    SRCS "main.cpp"
+    INCLUDE_DIRS "."
+)

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

@@ -0,0 +1,17 @@
+## IDF Component Manager Manifest File
+dependencies:
+  ## Required IDF version
+  idf:
+    version: '>=4.1.0'
+  # # 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

@@ -0,0 +1,35 @@
+#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

@@ -0,0 +1,4 @@
+build
+managed_components
+dependencies.lock
+sdkconfig.old

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

@@ -0,0 +1,17 @@
+# 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

@@ -0,0 +1,29 @@
+# 07_lcd-panel-i2c
+
+Using the ESP IDF for drawing to a LCD screen over I2C.
+
+For instructions on setting up the ESP-IDF see [04_-esp-idf-arduino](./../04_esp-idf-arduino)
+
+[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)
+
+Temperature and humidity sensor served on a web page within the local network.
+
+![example](./example.gif)
+
+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

@@ -0,0 +1,5 @@
+idf_component_register(
+    SRCS main.cpp display.cpp ssd1306.cpp i2c.h time_keeper.h panel.h panel_device.h
+    INCLUDE_DIRS .
+    REQUIRES driver
+)

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

@@ -0,0 +1,177 @@
+
+#include <esp_timer.h>
+
+#include <lv_init.h>
+
+#include <mutex>
+
+#include "display.h"
+
+// TODO: Remove this dependency by relocating SSD1306::oledb_buffer_
+#include "ssd1306.h"
+
+// LVGL library is not thread-safe, this example calls LVGL APIs from tasks.
+// We must use a mutex to protect it.
+_lock_t Display::ScopedLock::lv_lock_;
+
+// Static TimeKeeper for managing ESP timers across all displays.
+TimeKeeper Display::timers_;
+
+/// Tag used for ESP logging.
+const char * TAG = "Display";
+
+Display::Display(IPanelDevice &device) :
+    panel_(device),
+    lv_buf_(nullptr)
+{
+  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_);
+
+  register_draw_buffer();
+  register_lvgl_tick_timer();
+
+  ESP_LOGI(TAG, "Create LVGL FreeRTOS task");
+  xTaskCreate(Display::lvgl_port_task, "LVGL", LVGL_TASK_STACK_SIZE,
+              nullptr, LVGL_TASK_PRIORITY, nullptr);
+}
+
+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];
+
+  // Circular scroll.
+  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);
+}
+
+bool Display::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 Display::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.
+  // 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;
+
+  for (int32_t y = y1; y <= y2; y++) {
+    for (int32_t x = x1; x <= x2; x++) {
+      /* The order of bits 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
+      */
+      bool chroma_color = (px_map[(hor_res >> 3) * y + (x >> 3)] &
+                           1 << (7 - x % 8));
+
+      // Write to the buffer as required for the display.
+      // It writes only 1-bit for monochrome displays mapped vertically.
+      uint8_t *buf = SSD1306::oled_buffer_ + hor_res * (y >> 3) + (x);
+      if (chroma_color) {
+        (*buf) &= ~(1 << (y % 8));
+      } else {
+        (*buf) |= (1 << (y % 8));
+      }
+    }
+  }
+  // Pass the draw buffer to the driver.
+  ESP_ERROR_CHECK(
+      esp_lcd_panel_draw_bitmap(panel_handle, x1, y1, x2 + 1, y2 + 1,
+                                SSD1306::oled_buffer_));
+}
+
+void Display::lvgl_increase_tick_cb(void *)
+{
+  // Tell LVGL how many milliseconds has elapsed
+  lv_tick_inc(LVGL_TICK_PERIOD_MS);
+}
+
+[[noreturn]] void Display::lvgl_port_task(void *)
+{
+  ESP_LOGI(TAG, "Starting LVGL task");
+  for (uint32_t time_to_next_ms = 0; true; usleep(1000 * time_to_next_ms)) {
+    ScopedLock lock;
+    time_to_next_ms = lv_timer_handler();
+  }
+}
+
+void Display::register_draw_buffer()
+{
+  // Create draw buffer.
+  ESP_LOGI(TAG, "Allocate separate LVGL draw buffers");
+  lv_buf_ = heap_caps_calloc(1, panel_.device_->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(lv_display_, LV_COLOR_FORMAT_I1);
+  lv_display_set_buffers(lv_display_, lv_buf_, nullptr,
+                         panel_.device_->lv_buf_size_,
+                         LV_DISPLAY_RENDER_MODE_FULL);
+  lv_display_set_rotation(lv_display_, LV_DISPLAY_ROTATION_0);
+
+  ESP_LOGI(TAG, "Set LVGL callback for flushing to the display");
+  lv_display_set_flush_cb(lv_display_, Display::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 = Display::lvgl_flush_ready_cb,
+  };
+  ESP_ERROR_CHECK(
+      esp_lcd_panel_io_register_event_callbacks(panel_.esp_io_, &cbs,
+                                                lv_display_));
+}
+
+void Display::register_lvgl_tick_timer()
+{
+  ESP_LOGI(TAG, "Use esp_timer to increase LVGL tick");
+  const esp_timer_create_args_t esp_timer_args = {
+      .callback = &Display::lvgl_increase_tick_cb,
+      .name = "lvgl_tick"
+  };
+  timers_.start_new_timer_periodic(esp_timer_args, LVGL_TICK_PERIOD_MS * 1000);
+}

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

@@ -0,0 +1,143 @@
+#ifndef DISPLAY_H
+#define DISPLAY_H
+
+
+#include <widgets/label/lv_label.h>
+
+#include <unordered_map>
+
+#include "time_keeper.h"
+#include "panel.h"
+
+#define LVGL_TICK_PERIOD_MS    5
+#define LVGL_TASK_STACK_SIZE   (4 * 1024)
+#define LVGL_TASK_PRIORITY     2
+
+/**
+ * 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;
+
+  //
+  // GETTERS
+
+  /**
+   * Getter for accessing LVGL display handle.
+   *
+   * @sa ScopedLock for calling custom LVGL API's not implemented by Display.
+   */
+  [[nodiscard]] inline const lv_display_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_t *get() { return lv_display_; }
+
+  /// Dereference operator for accessing LVGL display handle.
+  [[nodiscard]] inline const lv_display_t *operator*() const { return get(); }
+
+  /// Dereference operator for accessing LVGL display handle.
+  [[nodiscard]] inline lv_display_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);
+
+  //
+  // TYPE DEFINITIONS
+
+  /**
+   * Obtains LVGL API mutex lock for the duration of local scope.
+   *
+   * LVGL library is not thread-safe, this example calls LVGL APIs from tasks.
+   */
+  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_;
+  };
+
+  //
+  // PUBLIC STATIC MEMBERS
+
+  /// Public static TimeKeeper for managing ESP timers across all displays.
+  static TimeKeeper timers_;
+
+private:
+  /// Registers LVGL draw buffers for this display.
+  void register_draw_buffer();
+
+  /// Registers LVGL ticker timer callback for rendering this display.
+  static void register_lvgl_tick_timer();
+
+  static bool lvgl_flush_ready_cb(esp_lcd_panel_io_handle_t panel,
+                                  esp_lcd_panel_io_event_data_t *data,
+                                  void *user_ctx);
+
+  static void lvgl_flush_cb(lv_display_t *display,
+                            const lv_area_t *area,
+                            uint8_t *px_map);
+
+  static void lvgl_increase_tick_cb(void *arg);
+
+  [[noreturn]] static void lvgl_port_task(void *arg);
+
+  //
+  // PRIVATE MEMBERS
+
+  /// Panel associated with this Display.
+  Panel panel_;
+
+  /// LVGL display handle.
+  lv_display_t *lv_display_;
+
+  /// LVGL draw buffer associated with this Display's lv_display_t.
+  void *lv_buf_;
+
+  /**
+   * 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_;
+};
+
+#endif // DISPLAY_H

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

@@ -0,0 +1,74 @@
+#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;
+
+  /**
+   * 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;
+  }
+
+  /// ESP I2C master bus configuration used during initialization.
+  i2c_master_bus_config_t esp_bus_config_;
+
+  /// RST GPIO pin number.
+  int rst_num_;
+
+private:
+  /// Tag used for ESP logging.
+  const char * TAG = "I2C";
+};
+
+#endif //I2C_H

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

@@ -0,0 +1,5 @@
+## IDF Component Manager Manifest File
+dependencies:
+  espressif/arduino-esp32: ^3.1.1
+  lvgl/lvgl: "9.2.0"
+  esp_lcd_sh1107: "^1"

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

@@ -0,0 +1,34 @@
+#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

@@ -0,0 +1,62 @@
+#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;
+
+  /// 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_;
+
+private:
+  /// Tag used for ESP logging.
+  const char * TAG = "Panel";
+};
+
+#endif //PANEL_H

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

@@ -0,0 +1,154 @@
+#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
+
+/**
+ * Encapsulates vendor specific ESP LCD pabel initialization logic.
+ * This pure virtual interface can be inherited from for using new LCD devices.
+ * See the SSD1306 example for implementing a PanelDevice 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) { }
+
+  virtual ~IPanelDevice() = default;
+
+  /**
+   * 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, "Install SSD1306 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;
+
+  /// 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_;
+
+private:
+  /**
+   * 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;
+
+  /// Tag used for ESP logging.
+  const char * TAG = "IPanelDevice";
+};
+
+#endif // PANEL_DEVICE_H

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

@@ -0,0 +1,6 @@
+
+#include "ssd1306.h"
+
+// To use LV_COLOR_FORMAT_I1 we need an extra buffer to hold the converted data.
+// TODO: Remove this and SSD1306 can be header only.
+uint8_t SSD1306::oled_buffer_[LCD_H_RES * LCD_V_RES / 8];

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

@@ -0,0 +1,110 @@
+/*
+ * https://docs.espressif.com/projects/esp-idf/en/v5.3.2/esp32/api-reference/peripherals/lcd/index.html#functional-overview
+ *
+ * Implementing the interface draw to an LCD using various interface modes.
+ * I2C interface mode is SSD1306
+ * SPI interface mode is ST7789
+ * I80 interface mode is NT35510 or ST7789
+ *
+ * Actually, I think any driver can be used with any interface mode
+ * Along with additional third party drivers via the component manager
+ * https://github.com/espressif/esp-idf/tree/0d6099ec533c4b647fb7a7b0b8942bc7aeb82f90/examples/peripherals/lcd/spi_lcd_touch#spi-lcd-and-touch-panel-example
+ */
+
+#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 LCD_H_RES              128
+#define LCD_V_RES              64
+#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,
+                       .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;
+
+  /**
+   * Provides the SSD1306 vendor configuration to IPanelDevice consumers.
+   *
+   * @return Address of the SSD1306 vendor configuration structure.
+   */
+  void *vendor_config() override
+  {
+    return &ssd1306_config_;
+  }
+
+  /// SSD1306 configuration structure.
+  esp_lcd_panel_ssd1306_config_t ssd1306_config_;
+
+  /**
+   * Draw buffer for this panel device.
+   * For LV_COLOR_FORMAT_I1 we need an extra buffer to hold the converted data.
+   */
+  static uint8_t oled_buffer_[LCD_H_RES * LCD_V_RES / 8];
+
+private:
+  /// 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));
+  }
+
+  /// Tag used for ESP logging.
+  const char * TAG = "SSD1306";
+};
+
+#endif // SSD1306_H

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

@@ -0,0 +1,138 @@
+
+#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 public way to access a Timer is by obtaining a TimerHandle (Timer *).
+ * 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;
+
+  /// Arguments passed to ESP API during timer creation.
+  esp_timer_create_args_t args_;
+
+  /// ESP timer handle.
+  esp_timer_handle_t esp_timer_;
+
+private:
+  /// Tag used for ESP logging.
+  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 *;
+
+  TimerHandle get_handle(const char *name)
+  {
+    return &managed_timers_.at(name);
+  }
+
+  TimerHandle operator[](const char *name) { return get_handle(name); }
+
+  /**
+   * 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*)
+   */
+  TimerHandle create_timer(esp_timer_create_args_t args)
+  {
+    auto rt = managed_timers_.emplace(args.name, args);
+    if (!rt.second) {
+      ESP_LOGE(TAG, "Display::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)
+  {
+    managed_timers_.erase(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:
+  /// Existing ESP timers created for this TimeKeeper instance.
+  std::unordered_map<const char *, Timer> managed_timers_;
+
+  /// Tag used for ESP logging.
+  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