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--- iothings:proiecte:2025sric:ledstrip [2025/05/28 23:39]
andrei.besliu [ESP32 Web-based LED strip]
+++ iothings:proiecte:2025sric:ledstrip [2025/05/29 00:48] (current)
andrei.besliu [ESP32 Web-based LED strip]
@@ Line 1: / Line 1: @@
-====== ESP32 Web-based LED strip ======
+====== ESP32 BLE-based LED strip ======
   * Author: Besliu Andrei-Cornel
@@ Line 5: / Line 5: @@
   * Master: SCPD
   * Video Link: https://youtu.be/Q6bHqYo0OGY
-  * Source Code: TBD
+  * Source Code: {{:iothings:proiecte:2025sric:besliu_andrei_iot.zip}}
 ====== Introduction ======
-Provide smart lighting to a home using an RGB LED strip and an ESP32. The ESP32 will act as a web server, accessible from devices such as a smartphone or desktop PC.
+Provide smart lighting to a home using an RGB LED strip and an ESP32. The ESP32 will expose a BLE server that can receive commands from any BLE client. To prove functionality I implemented some simple features such as selecting from a number of preset colors and adjusting brightness.
-====== Context ======
 ====== Hardware ======
+  * **ESP32-WROOM-32:** 1 x ESP32 Sparrow development board
+  * **NeoPixel LED Strip:** 1 x 5m NeoPixel LED strip, 300 LED's.
+  * **Breadboard:** 1x Breadboard for securing connections.
+  * **Connecting Cables**
+  * **USB-A to micro USB cable**
+====== Diagram ======
+{{ :iothings:proiecte:2025sric:diagram_ledstrip.png }}
+====== Actual Hardware ======
+{{ :iothings:proiecte:2025sric:actualHw_ledStrip.jpeg?500 |}}
+The NeoPixel LED strip need +5V and GND to power the LED's and the addresing is done using a single data pin, which I have connected to GPIO 17.
 ====== Software ======
-=== Code Snippets ===
+   * Arduino IDE for development
+   * Adafruit_NeoPixel library for easy LED strip manipulation
+   * ArduinoBLE library for Bluetooth service.
-==== Firebase ====
+====== Code Snippets ======
+Setting up BLE service with 2 Characteristics, one for setting the color and one for setting the brightness. The color receives a string
+with the desired color ("red", "blue", "yellow", "green", "purple", "orange", "cyan") and the brightness is a single 8-bit value where 0 is off and 255 is the highest possible brightness.
+<code C++>
+// BLE server callback
+class MyServerCallbacks: public BLEServerCallbacks {
+  void onConnect(BLEServer* pServer) {
+    deviceConnected = true;
+  };
+  void onDisconnect(BLEServer* pServer) {
+    deviceConnected = false;
+  }
+};
+/* BLE Characteristics */
+BLECharacteristic *colorCharacteristic;
+class ColorCallback: public BLECharacteristicCallbacks {
+  void onWrite(BLECharacteristic *colorCharacteristic) {
+    receivedColor = colorCharacteristic->getValue();
+    if (receivedColor.length() > 0) {
+      Serial.print("Received Color: ");
+      Serial.println(receivedColor.c_str());
+    }
+  }
+};
+BLECharacteristic *brightCharacteristic;
+class BrightnessCallback: public BLECharacteristicCallbacks {
+  void onWrite(BLECharacteristic *brightCharacteristic) {
+    receivedBrightness = brightCharacteristic->getValue().c_str()[0];
+    Serial.print("Received Brightness: ");
+    Serial.println(receivedBrightness, DEC);
+  }
+};
+[ ... ]
+// Initialize BLE
+BLEDevice::init("ESP32_LED_Strip");
+BLEServer *pServer = BLEDevice::createServer();
+pServer->setCallbacks(new MyServerCallbacks());
+BLEService *bmeService = pServer->createService(SERVICE_UUID);
+// Create colorCharacteristic
+colorCharacteristic = bmeService->createCharacteristic(
+                    COLOR_UUID,
+                    BLECharacteristic::PROPERTY_READ |
+                    BLECharacteristic::PROPERTY_WRITE
+                );
+colorCharacteristic->setCallbacks(new ColorCallback());
+colorCharacteristic->setValue("Hello, World!");
+// Create colorCharacteristic
+brightCharacteristic = bmeService->createCharacteristic(
+                    BRIGHTNESS_UUID,
+                    BLECharacteristic::PROPERTY_READ |
+                    BLECharacteristic::PROPERTY_WRITE
+                );
+brightCharacteristic->setCallbacks(new BrightnessCallback());
+int defaultBrightness = 255;
+brightCharacteristic->setValue(defaultBrightness);
+// Start bme service.
+bmeService->start();
+// Start Advertising
+pServer->getAdvertising()->start();
+Serial.println("Waiting a client connection to notify...");
+</code>
+Setting up the LedStrip and control logic is straight-forward. We have global variables holding the current state of the strip that get update on BLECallback triggers. We also have a chgStrip boolean that prevents unneccesary updating of the LedStrip if no changes are currently performed.
+<code c++>
+// Initialize the NeoPixel library
+strip.begin();
+// Set all pixels to 'off'
+strip.show();
+// Set some default strip values;
+actualBrightness = 128;
+actualColor = strip.Color(0, 75, 0); // moderately bright green
+chgStrip = true;
+[ ... ]
+// Check if a device was connected
+if (deviceConnected) {
+  if (!receivedColor.isEmpty()) {
+    actualColor = getColor(receivedColor);
+    receivedColor = "";
+    chgStrip = true;
+  }
+  if (receivedBrightness != 0) {
+    actualBrightness = receivedBrightness;
+    receivedBrightness = 0;
+    chgStrip = true;
+  }
+}
+// Update Strip.
+if (chgStrip) {
+  strip.clear();
+  for(int i=0; i<NUM_PIXELS; i++) { // For each pixel...
+    strip.setPixelColor(i, actualColor);
+  }
+  strip.setBrightness(actualBrightness);
+  strip.show();
+  // Do not change strip next cycle
+  chgStrip = false;
+}
+</code>
 ====== Challenges ======
-====== References ======
+Not having proper soldering tools leads to bad electrical contacts and makes it a nightmare to debug any issues. Thankfully, jamming a wire through the ESP32 DevBoard pins worked brilliantly, just don't ask me to move it anywhere.
+Initially I wanted to use both BLE and a webpage hosted on the ESP32 itself to allow control of the LED strip from multiple sources but due to memory constraints on the ESP32 I had to choose only one (91% memory usage with the BLE implementation alone).
+I find it very annoying how BLE handles characteristics, only having a predefined set of BLEUUID's available to pick and choose from. For example, the was no readily available UUID for brightness or color, just a generic "LED Array" or "Led Strip".
+I choose BLE due to the easy implementaion as baking-in a HTML page in the Arduino IDE seems janky to me. The right way to approach would be by installing a lightweight RTOS such as NuttX or freeRTOS and ditching the BLE for a more customizable webpage, as in our case  battery and power constraints are irrelevant.
+====== References ======
+  * Adafruit_NeoPixel: https://github.com/adafruit/Adafruit_NeoPixel
+  * ArduinoBle: https://docs.arduino.cc/libraries/arduinoble/
+  * Our OCW labs.
+  * Some helpful StackOverflow threads.