ESP32 Wi-Fi Connection Failure

Ensure that the SSID and password are correct. Pay attention to uppercase and lowercase letters, spaces, and special characters. Common mistakes include:

• Mistyping the network name (SSID)
• Using incorrect password case
• Overlooking hidden characters in the password

To verify:

1. Print the SSID and password in your serial monitor for debugging.
2. Try connecting to the same network with another device to confirm the credentials.
3. Temporarily disable network security to test if it’s a credential issue.

Weak signal strength can cause connection failures. To improve signal strength:

1. Move the ESP32 closer to the Wi-Fi router.
2. Use a Wi-Fi analyzer app on your smartphone to check signal strength in the area.
3. Consider using an external antenna for better reception.
4. Implement a retry mechanism in your code to attempt reconnection multiple times.

Example code for signal strength check:

#include <WiFi.h>

void setup() {
  Serial.begin(115200);
  WiFi.begin("YourSSID", "YourPassword");
  
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
    
    // Print the signal strength
    Serial.print("Signal strength (RSSI): ");
    Serial.print(WiFi.RSSI());
    Serial.println(" dBm");
  }
}

Make sure your router is using a compatible security protocol. The ESP32 supports:

• Open networks (not recommended for security reasons)
• WEP (outdated and not secure)
• WPA/WPA2 Personal (recommended)

Check steps to verify and adjust.

To isolate the issue, try connecting to a different Wi-Fi network:

1. Create a mobile hotspot using your smartphone.
2. Update your ESP32 code with the new network credentials.
3. Attempt to connect to this new network.

If successful, the problem may be with your original network configuration. If it still fails, the issue is likely with the ESP32 itself or your code.

Use a simple Wi-Fi scanning sketch to ensure the ESP32’s Wi-Fi hardware is working correctly:

#include <WiFi.h>

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);
  WiFi.disconnect();
  delay(100);
}

void loop() {
  Serial.println("Scanning for Wi-Fi networks...");
  int n = WiFi.scanNetworks();
  if (n == 0) {
    Serial.println("No networks found");
  } else {
    for (int i = 0; i < n; ++i) {
      Serial.printf("%d: %s (%d dBm)\n", i + 1, WiFi.SSID(i).c_str(), WiFi.RSSI(i));
    }
  }
  delay(5000);
}

This code will scan for available networks and print them to the serial monitor. If no networks are found, there may be an issue with the Wi-Fi hardware.

Unstable power can cause Wi-Fi connection problems. Ensure a stable power supply:

1. Use a high-quality USB cable for programming and power.
2. Provide a separate, stable 3.3V power supply for your project.
3. Add a large capacitor (e.g., 1000µF) between VCC and GND to stabilize power.
4. Monitor power consumption during Wi-Fi operations and ensure your supply can handle peak currents.
   
   See also: ESP32 Brownout Reset Error for more power-related troubleshooting.