This week's assignment consisted of exploring the remote connectivity capabilities of our microcontrollers. For this, we carried out a group exercise between our boards and an individual one.
To enable wireless communication, we will initially attempt to create an interaction via Wi-Fi, using an MQTT broker for communication.
An MQTT broker is a server that manages communication between devices using the MQTT protocol. It receives messages from clients (publishers) and routes them to the appropriate recipients (subscribers), enabling lightweight and efficient machine-to-machine communication, especially over Wi-Fi or the internet. We attempted to test its functionality, but the signal tended to drop quickly and was not reliable for long-term use, so we opted to switch to Bluetooth instead
Ofelia and I had already designed and fabricated our boards during weeks 6 and 8. Therefore, for this group assignment, we chose to establish communication between them. In this part of the assignment, I will present my code and explain the testing process I followed.
1. As a first step, it is necessary to use the multimeter to properly understand what is happening electrically within our board.q
2. To start, we needed to connect to a broker server using MQTT Broker, with each device connected to a Wi-Fi network. In my case, I used my phone's hotspot to ensure a stable connection.
3. Button to Servo A code is designed that, in the first block, sets up the Wi-Fi service for the connection. Then, it defines the behavior of each pin for signal control, and finally, it registers the looped action that will occur when the button is pressed.
#include #include // Wi-Fi const char* ssid = "OfeliA phone"; const char* password = "xxxxxxxxxx"; // MQTT const char* mqtt_server = "broker.hivemq.com"; WiFiClient espClient; PubSubClient client(espClient); const int botonPin = 3; // button pin bool lastButtonState = HIGH; // to avoid repeating String lastSent = ""; void setup() { Serial.begin(115200); pinMode(botonPin, INPUT_PULLUP); WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println("WiFi conectado"); // connected client.setServer(mqtt_server, 1883); while (!client.connected()) { Serial.print("Conectando a MQTT..."); if (client.connect("ButtonClient")) { Serial.println("conectado"); } else { Serial.print("falló, rc="); Serial.print(client.state()); delay(5000); } } }const int botonPin = 3; // button pin bool lastButtonState = HIGH; // to avoid repeating String lastSent = ""; void setup() { Serial.begin(115200); pinMode(botonPin, INPUT_PULLUP); WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println("WiFi conectado"); // connected client.setServer(mqtt_server, 1883); while (!client.connected()) { Serial.print("Conectando a MQTT..."); if (client.connect("ButtonClient")) { Serial.println("conectado"); } else { Serial.print("falló, rc="); Serial.print(client.state()); delay(5000); } } }
4. Potentiometer to Led RGB Another code is designed to connect the potentiometer to the LED. First, it initiates the Wi-Fi request, then identifies the pins used for the potentiometer, and scales its resistance value to a range from 0 to 255 to control the LED's color.
#include #include // Wi-Fi const char* ssid = "OfeliA phone"; const char* password = "xxxxxxxxxx"; // MQTT const char* mqtt_server = "broker.hivemq.com"; WiFiClient espClient; PubSubClient client(espClient); int ledRojo = 10; int ledVerde = 9; int ledAzul = 8; WiFiClient espClient; // Create a WiFi client instance PubSubClient client(espClient); // Create a MQTT client instance void setup() { pinMode(ledRojo, OUTPUT); pinMode(ledVerde, OUTPUT); pinMode(ledAzul, OUTPUT); Serial.begin(115200); // Start the serial communication delay(10); // Connect to Wi-Fi WiFi.begin(ssid, password); // Connect to WiFi network while (WiFi.status() != WL_CONNECTED) { // Wait for WiFi connection delay(500); Serial.print("."); } Serial.println("WiFi connected"); // Connect to MQTT Broker client.setServer(mqtt_server, 1883); // Set the MQTT broker server and port client.setCallback(callback); // Set callback function to handle incoming messages while (!client.connected()) { // Attempt to connect to MQTT broker Serial.print("Attempting MQTT connection..."); if (client.connect("ESP32C3Client")) { // Client ID for MQTT connection Serial.println("connected"); client.subscribe("arduino/uno"); // Subscribe to the topic "arduino/uno" } else { Serial.print("failed, rc="); Serial.print(client.state()); // Print connection status Serial.println(" try again in 5 seconds"); delay(5000); // Wait 5 seconds before retrying } } } void loop() { client.loop(); // Maintain MQTT connection and handle incoming messages } // MQTT callback function to handle incoming messages void callback(char* topic, byte* payload, unsigned int length) { Serial.print("Message arrived ["); Serial.print(topic); // Print the topic of the incoming message Serial.print("] "); String msg; // Print the incoming message for (int i = 0; i < length; i++) { msg += (char)payload[i]; } Serial.println(msg); if (msg == "A") { // 10 combinaciones de magenta analogWrite(ledRojo, 50); // más brillante analogWrite(ledVerde, 255); // verde apagado analogWrite(ledAzul, 80); // más brillante Serial.println("Magenta combo 1"); } else if (msg == "S") { analogWrite(ledRojo, 70); analogWrite(ledVerde, 255); analogWrite(ledAzul, 60); Serial.println("Magenta combo 2"); } else if (msg == "D") { analogWrite(ledRojo, 90); analogWrite(ledVerde, 255); analogWrite(ledAzul, 40); Serial.println("Magenta combo 3"); } else if (msg == "F") { analogWrite(ledRojo, 110); analogWrite(ledVerde, 255); analogWrite(ledAzul, 30); Serial.println("Magenta combo 4"); } else if (msg == "G") { analogWrite(ledRojo, 130); analogWrite(ledVerde, 255); analogWrite(ledAzul, 20); Serial.println("Magenta combo 5"); } else if (msg == "H") { analogWrite(ledRojo, 150); analogWrite(ledVerde, 255); analogWrite(ledAzul, 15); Serial.println("Magenta combo 6"); } else if (msg == "I") { analogWrite(ledRojo, 170); analogWrite(ledVerde, 255); analogWrite(ledAzul, 10); Serial.println("Magenta combo 7"); } else if (msg == "J") { analogWrite(ledRojo, 190); analogWrite(ledVerde, 255); analogWrite(ledAzul, 5); Serial.println("Magenta combo 8"); } else if (msg == "K") { analogWrite(ledRojo, 210); analogWrite(ledVerde, 255); analogWrite(ledAzul, 2); Serial.println("Magenta combo 9"); } else if (msg == "L") { analogWrite(ledRojo, 230); analogWrite(ledVerde, 255); analogWrite(ledAzul, 0); Serial.println("Magenta combo 10"); } }
5. Final visualization of both Arduinos running in parallel and exchanging information.
6. A second exercise was developed to validate the use of Bluetooth. In this case, the goal was to create a remote camera trigger using Bluetooth Low Energy between the Seeed board and my cellphone.
7. The first part of the code for the action will be used to call the BLE and HID libraries (to emulate a keyboard) and define the action pins..
#include #include #include #include #include #define swPin D1 // Joystick SW button on D1 BLEHIDDevice* hid; BLECharacteristic* input; int lastButtonState = HIGH; // Pull-up, button press is LOW bool deviceConnected = false;
8. The next block defines the BLE behavior so that it can be detected and recognized by the cellphone. It also begins assigning a code to each function of the simulated HID keyboard.
class MyServerCallbacks: public BLEServerCallbacks { void onConnect(BLEServer* pServer) { deviceConnected = true; Serial.println("Device connected"); } void onDisconnect(BLEServer* pServer) { deviceConnected = false; Serial.println("Device disconnected"); } }; void setup() { // Empty setup } void loop() { // One-time initialization static bool initialized = false; if (!initialized) { Serial.begin(115200); BLEDevice::init("XIAO_ESP32C3"); BLEServer* pServer = BLEDevice::createServer(); pServer->setCallbacks(new MyServerCallbacks()); hid = new BLEHIDDevice(pServer); input = hid->inputReport(1); hid->manufacturer()->setValue("Seeed"); hid->pnp(0x02, 0xe502, 0xa111, 0x0210); hid->hidInfo(0x00, 0x01); hid->reportMap((uint8_t[]) { 0x05, 0x01, // Usage Page (Generic Desktop) 0x09, 0x0D, // Usage (Camera) 0xA1, 0x01, // Collection (Application) 0x85, 0x01, // Report ID (1) 0x05, 0x01, // Usage Page (Generic Desktop) 0x09, 0x6D, // Usage (System Camera Shutter) 0x15, 0x00, // Logical Minimum (0) 0x25, 0x01, // Logical Maximum (1) 0x75, 0x01, // Report Size (1) 0x95, 0x01, // Report Count (1) 0x81, 0x02, // Input (Data,Var,Abs) 0x95, 0x07, // Report Count (7) 0x81, 0x03, // Input (Const) 0xC0 // End Collection }, 20); hid->startServices(); BLEDevice::getAdvertising()->start(); Serial.println("BLE HID Advertising Started"); pinMode(swPin, INPUT_PULLUP); initialized = true; }
9. The third part is responsible for enabling constant reconnection to avoid issues with loss of control.
if (!deviceConnected) { BLEDevice::getAdvertising()->start(); Serial.println("Restarting advertising..."); delay(500); }
10. Finally, the action block is generated to detect the joystick click and convert it into a signal interpretable by the cellphone.
int buttonState = digitalRead(swPin); if (buttonState == LOW && lastButtonState == HIGH) { if (deviceConnected) { uint8_t report[] = {1}; // Camera shutter press input->setValue(report, sizeof(report)); input->notify(); delay(10); report[0] = 0; // Release input->setValue(report, sizeof(report)); input->notify(); Serial.println("Button pressed - Camera shutter sent successfully"); } else { Serial.println("Button pressed - No device connected"); } delay(50); } lastButtonState = buttonState; }
10. The final step will be to review the outcome of the experiment and identify the issues that need to be resolved.
11. The final step will be to review the outcome of the experiment and identify the issues that need to be resolved.
The code includes the BleKeyboard.h library to enable BLE keyboard functionality, defines pin 14 (JOYSTICK_SW_PIN) for the joystick switch, and creates a "VolumeControl" BLE keyboard object with manufacturer "ESP32" and a 100% battery level. It also initializes buttonPressStart to track press duration and sets STUCK_THRESHOLD to 2000ms (2 seconds) to detect a stuck button, setting up the core hardware and logic.
#include // Definir el pin del botón del joystick (SW) #define JOYSTICK_SW_PIN 14 // Crear objeto de teclado Bluetooth BleKeyboard bleKeyboard("VolumeControl", "ESP32", 100); // Variables para detectar botón atascado unsigned long buttonPressStart = 0; const unsigned long STUCK_THRESHOLD = 2000; // 2 segundos (en milisegundos)
The setup function starts serial communication at 115200 baud for debugging, configures pin 14 as an input with a pull-up resistor, and initiates the BLE keyboard service with bleKeyboard.begin(), printing a message to indicate it’s waiting for a Bluetooth connection, preparing the device for operation.
void setup() { // Iniciar comunicación serial para depuración Serial.begin(115200); // Configurar el pin SW del joystick como entrada con pull-up interno pinMode(JOYSTICK_SW_PIN, INPUT_PULLUP); // Iniciar el teclado Bluetooth bleKeyboard.begin(); Serial.println("Esperando conexión Bluetooth..."); }
The loop function checks if the BLE keyboard is connected; if so, it detects a button press (LOW due to pull-up) and, on the first press, records the start time, sends a KEY_MEDIA_VOLUME_DOWN command, releases the key, and adds a 200ms debounce delay. It alerts if the button is stuck for 2 seconds or more, resets the timer on release, and, if disconnected, prints a waiting message every second, utilizing the ESP32-C3's GPIO and BLE for volume control.
void loop() { // Verificar si el teclado está conectado if (bleKeyboard.isConnected()) { // Leer el estado del pin SW (LOW cuando se presiona el joystick) if (digitalRead(JOYSTICK_SW_PIN) == LOW) { // Si es la primera vez que se detecta la presión if (buttonPressStart == 0) { buttonPressStart = millis(); // Guardar el tiempo de inicio Serial.println("Joystick presionado, enviando tecla de bajar volumen..."); // Enviar la tecla multimedia de bajar volumen bleKeyboard.write(KEY_MEDIA_VOLUME_DOWN); // Liberar la tecla bleKeyboard.releaseAll(); // Pequeña espera para evitar rebotes delay(200); } // Verificar si el botón está atascado if (millis() - buttonPressStart >= STUCK_THRESHOLD) { Serial.println("¡ALERTA! El botón del joystick está atascado."); // Puedes agregar más acciones aquí, como detener el envío de comandos } } else { // Botón no presionado, reiniciar el temporizador if (buttonPressStart != 0) { Serial.println("Joystick liberado."); buttonPressStart = 0; // Reiniciar el temporizador } } } else { Serial.println("Bluetooth no conectado. Esperando conexión..."); delay(1000); // Reducir la frecuencia de este mensaje } }
The final result is positive, and unlike the first test, the inclusion of delay(200) effectively prevents the key from remaining pressed, which previously hindered the process of taking photographs.
Arduino Code of Button to Servo Arduino Code of Potentiometer to LED Arduino Code of Personal project