Add I2C scanner example.

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

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+## 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

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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();
+}