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graph TB
ESP32["ESP32 Soft AP<br/>192.168.4.1"]
Client1["Phone<br/>192.168.4.2"]
Client2["Laptop<br/>192.168.4.3"]
Client3["Tablet<br/>192.168.4.4"]
ESP32 -.->|"SSID: ESP32-IoT-AP<br/>Password: <setup password>"| Client1
ESP32 -.->|"DHCP Assigns IP"| Client2
ESP32 -.->|"Wi-Fi Channels 1-11 (2.4 GHz)"| Client3
style ESP32 fill:#2C3E50,stroke:#16A085,stroke-width:3px,color:#fff
style Client1 fill:#E67E22,stroke:#2C3E50,stroke-width:2px
style Client2 fill:#E67E22,stroke:#2C3E50,stroke-width:2px
style Client3 fill:#E67E22,stroke:#2C3E50,stroke-width:2px
846 Wi-Fi Implementation: ESP32 Basics
846.1 Learning Objectives
By the end of this chapter, you will be able to:
- Configure ESP32 Station Mode: Connect ESP32 devices to existing Wi-Fi networks with proper error handling
- Implement Access Point Mode: Create Wi-Fi hotspots for device configuration and local control
- Scan Available Networks: Discover and analyze nearby Wi-Fi networks including security types
- Handle Connection Events: Implement reconnection logic and status monitoring
- Use SmartConfig Provisioning: Configure Wi-Fi credentials without hardcoding them
TipFor Beginners: Getting Started with ESP32 Wi-Fi
What is this chapter? Practical ESP32 Wi-Fi programming including station mode, access point mode, and network scanning.
When to use: - When building your first Wi-Fi-connected IoT device - When you need to configure Wi-Fi on ESP32/ESP8266 - Before implementing more complex Wi-Fi applications
Key Topics:
| Topic | Application |
|---|---|
| Station Mode | Connect device to existing network |
| AP Mode | Create device hotspot |
| Network Scanning | Discover available networks |
| SmartConfig | Provision credentials wirelessly |
Prerequisites: - Wi-Fi fundamentals knowledge - Basic C/C++ programming - Understanding of TCP/IP basics
846.2 Prerequisites
Before diving into this chapter, you should be familiar with:
- Wi-Fi Fundamentals and Standards: Understanding Wi-Fi standards, frequency bands, and basic Wi-Fi characteristics
- Wi-Fi Architecture and Mesh: Knowledge of infrastructure mode, Wi-Fi Direct, and mesh networking
- C/C++ Programming: Basic programming skills for ESP32 code examples
846.3 Hands-on: ESP32 Wi-Fi Configuration
846.3.1 Basic Wi-Fi Connection
// ESP32 Wi-Fi Station Mode - Basic Connection
#include <Wi-Fi.h>
// Wi-Fi credentials
const char* ssid = "YourNetworkSSID";
const char* password = "YourPassword";
void setup() {
Serial.begin(115200);
delay(1000);
// Connect to Wi-Fi
Serial.println("Connecting to Wi-Fi...");
Wi-Fi.mode(WIFI_STA); // Station mode
Wi-Fi.begin(ssid, password);
// Wait for connection
int attempts = 0;
while (Wi-Fi.status() != WL_CONNECTED && attempts < 20) {
delay(500);
Serial.print(".");
attempts++;
}
if (Wi-Fi.status() == WL_CONNECTED) {
Serial.println("\nWi-Fi connected!");
Serial.print("IP address: ");
Serial.println(Wi-Fi.localIP());
Serial.print("MAC address: ");
Serial.println(Wi-Fi.macAddress());
Serial.print("Signal strength (RSSI): ");
Serial.print(Wi-Fi.RSSI());
Serial.println(" dBm");
} else {
Serial.println("\nFailed to connect to Wi-Fi");
}
}
void loop() {
// Check Wi-Fi connection status
if (Wi-Fi.status() != WL_CONNECTED) {
Serial.println("Wi-Fi disconnected! Reconnecting...");
Wi-Fi.reconnect();
}
delay(10000);
}
WarningSecurity Note
These examples inline SSID/password for clarity. For production IoT, avoid hardcoding credentials: use a provisioning flow (BLE/SoftAP/SmartConfig as appropriate) and store credentials in NVS protected by flash encryption/secure boot where supported. See Wi-Fi Security and Provisioning.
TipInteractive Simulator: ESP32 Wi-Fi Connection
Try it yourself! See how ESP32 connects to Wi-Fi networks and retrieves network information.
What This Simulates: An ESP32 connecting to a Wi-Fi network in Station (STA) mode, displaying connection status, IP address, and signal strength.
How to Use: 1. Click Start Simulation 2. Watch the Serial Monitor show connection progress 3. Observe the Wi-Fi connection status LEDs 4. See the IP address assignment (DHCP) 5. Monitor signal strength (RSSI) readings 6. Try modifying credentials to see connection failures
846.3.2 Wi-Fi with Auto-Reconnect
// ESP32 Wi-Fi with Automatic Reconnection
#include <Wi-Fi.h>
const char* ssid = "YourSSID";
const char* password = "YourPassword";
void connectWiFi() {
if (Wi-Fi.status() != WL_CONNECTED) {
Serial.print("Connecting to Wi-Fi");
Wi-Fi.begin(ssid, password);
int timeout = 0;
while (Wi-Fi.status() != WL_CONNECTED && timeout < 30) {
delay(500);
Serial.print(".");
timeout++;
}
if (Wi-Fi.status() == WL_CONNECTED) {
Serial.println("\nConnected!");
Serial.println("IP: " + Wi-Fi.localIP().toString());
} else {
Serial.println("\nConnection failed!");
}
}
}
void setup() {
Serial.begin(115200);
// Configure Wi-Fi for low power
Wi-Fi.mode(WIFI_STA);
Wi-Fi.setAutoReconnect(true);
Wi-Fi.persistent(false); // Don't save Wi-Fi config to flash
connectWiFi();
}
void loop() {
// Your IoT logic here
// Periodic connection check
static unsigned long lastCheckMs = 0;
if (millis() - lastCheckMs >= 30000) { // Every 30 seconds
lastCheckMs = millis();
if (Wi-Fi.status() != WL_CONNECTED) {
connectWiFi();
}
}
}846.3.3 Wi-Fi Scanning (Find Available Networks)
// ESP32 Wi-Fi Network Scanner
#include <Wi-Fi.h>
void setup() {
Serial.begin(115200);
Wi-Fi.mode(WIFI_STA);
Wi-Fi.disconnect();
delay(100);
Serial.println("Scanning Wi-Fi networks...");
}
void loop() {
int n = Wi-Fi.scanNetworks();
Serial.println("\n=== Wi-Fi Scan Results ===");
if (n == 0) {
Serial.println("No networks found");
} else {
Serial.printf("Found %d networks:\n", n);
for (int i = 0; i < n; i++) {
Serial.printf("%2d: %-32s ", i + 1, Wi-Fi.SSID(i).c_str());
Serial.printf("(%3d dBm) ", Wi-Fi.RSSI(i));
Serial.printf("CH:%2d ", Wi-Fi.channel(i));
// Security type
switch (Wi-Fi.encryptionType(i)) {
case WIFI_AUTH_OPEN:
Serial.print("[OPEN]");
break;
case WIFI_AUTH_WEP:
Serial.print("[WEP]");
break;
case WIFI_AUTH_WPA_PSK:
Serial.print("[WPA]");
break;
case WIFI_AUTH_WPA2_PSK:
Serial.print("[WPA2]");
break;
case WIFI_AUTH_WPA_WPA2_PSK:
Serial.print("[WPA/WPA2]");
break;
#ifdef WIFI_AUTH_WPA2_WPA3_PSK
case WIFI_AUTH_WPA2_WPA3_PSK:
Serial.print("[WPA2/WPA3]");
break;
#endif
#ifdef WIFI_AUTH_WPA3_PSK
case WIFI_AUTH_WPA3_PSK:
Serial.print("[WPA3]");
break;
#endif
case WIFI_AUTH_WPA2_ENTERPRISE:
Serial.print("[WPA2-ENT]");
break;
default:
Serial.print("[UNKNOWN]");
}
Serial.println();
}
}
delay(10000); // Scan every 10 seconds
}
TipInteractive Simulator: Wi-Fi Network Scanner
Try it yourself! See how ESP32 scans and discovers available Wi-Fi networks.
What This Simulates: An ESP32 performing Wi-Fi network scans to discover nearby access points, displaying SSID, signal strength, channel, and security type.
How to Use: 1. Click Start Simulation 2. Watch the Serial Monitor show discovered networks 3. Observe network details: SSID, RSSI (dBm), channel, security 4. See how scan results update periodically 5. Notice different security protocols (OPEN, WPA2, etc.)
846.3.4 ESP32 as Access Point (Soft AP)
// ESP32 as Wi-Fi Access Point
#include <Wi-Fi.h>
const char* ap_ssid = "ESP32-IoT-AP";
const char* ap_password = "12345678"; // Min 8 characters
void setup() {
Serial.begin(115200);
// Configure Access Point
Wi-Fi.softAP(ap_ssid, ap_password);
IPAddress IP = Wi-Fi.softAPIP();
Serial.println("Access Point Started");
Serial.print("AP IP address: ");
Serial.println(IP);
Serial.print("AP SSID: ");
Serial.println(ap_ssid);
// Optional: Configure AP with more parameters
// Wi-Fi.softAP(ssid, password, channel, hidden, max_connections)
// Wi-Fi.softAP(ap_ssid, ap_password, 6, false, 4);
}
void loop() {
// Check connected clients
Serial.printf("Connected stations: %d\n", Wi-Fi.softAPgetStationNum());
delay(5000);
}
TipInteractive Simulator: ESP32 Access Point Mode
Try it yourself! See how ESP32 creates its own Wi-Fi network that other devices can connect to.
What This Simulates: An ESP32 running as a Wi-Fi Access Point (Soft AP), allowing other devices to connect and displaying the number of connected clients.
How to Use: 1. Click Start Simulation 2. Watch the Serial Monitor show AP configuration 3. See the AP IP address (typically 192.168.4.1) 4. Observe connected station count updates 5. Notice the ESP32 becomes a Wi-Fi router!
846.3.5 Wi-Fi Provisioning (SmartConfig)
// ESP32 Wi-Fi Provisioning with SmartConfig
#include <Wi-Fi.h>
void setup() {
Serial.begin(115200);
Wi-Fi.mode(WIFI_STA);
// Start SmartConfig
Serial.println("Starting SmartConfig...");
Serial.println("Use a SmartConfig-compatible app to provide Wi-Fi credentials");
Wi-Fi.beginSmartConfig();
// Wait for SmartConfig completion
while (!Wi-Fi.smartConfigDone()) {
delay(500);
Serial.print(".");
}
Serial.println("\nSmartConfig received!");
Serial.println("Connecting to Wi-Fi...");
// Wait for Wi-Fi connection
while (Wi-Fi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("\nWi-Fi Connected!");
Serial.print("IP Address: ");
Serial.println(Wi-Fi.localIP());
// Save credentials (optional)
Serial.println("SSID: " + Wi-Fi.SSID());
}
void loop() {
// Your application code
}846.4 Raspberry Pi Wi-Fi Configuration
For a quick overview, see Wi-Fi Fundamentals and Standards. Below are CLI-first options commonly used in IoT deployments.
846.4.1 Option A: NetworkManager (nmcli)
sudo nmcli dev wifi list
sudo nmcli dev wifi connect "<SSID>" password "<PASSWORD>" ifname wlan0
ip -br a show wlan0
ping -c 3 1.1.1.1846.4.2 Option B: wpa_supplicant (legacy / minimal images)
Edit /etc/wpa_supplicant/wpa_supplicant.conf:
country=US
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
network={
ssid="YourNetworkSSID"
psk="YourPassword"
}WPA2-Enterprise (example; validate server certificates):
network={
ssid="Enterprise-Wi-Fi"
key_mgmt=WPA-EAP
eap=PEAP
identity="username"
password="password"
ca_cert="/etc/ssl/certs/your_ca.pem"
phase2="auth=MSCHAPV2"
}Apply and verify:
sudo wpa_cli -i wlan0 reconfigure
sudo systemctl restart dhcpcd || true
ip -br a show wlan0
iw dev wlan0 link846.4.3 Python Wi-Fi Client (MQTT over Wi-Fi)
# Python Wi-Fi-enabled MQTT IoT Sensor
import paho.mqtt.client as mqtt
import time
import random
# MQTT Configuration
MQTT_BROKER = "192.168.1.100" # Local broker or cloud
MQTT_PORT = 1883
MQTT_TOPIC = "home/sensors/temperature"
# Callback signature for paho-mqtt 2.0+
def on_connect(client, userdata, flags, reason_code, properties):
if reason_code == 0:
print("Connected to MQTT broker via Wi-Fi")
else:
print(f"Connection failed with reason code {reason_code}")
def on_publish(client, userdata, mid):
print(f"Message {mid} published")
# Create MQTT client (paho-mqtt 2.0+ API)
client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2, client_id="RaspberryPi-Sensor")
client.on_connect = on_connect
client.on_publish = on_publish
# Connect to broker
try:
client.connect(MQTT_BROKER, MQTT_PORT, 60)
client.loop_start()
while True:
# Simulate sensor reading
temperature = round(20 + random.uniform(-5, 5), 2)
# Publish to MQTT
result = client.publish(MQTT_TOPIC, str(temperature))
print(f"Published temperature: {temperature}C (QoS: {result.rc})")
time.sleep(10) # Publish every 10 seconds
except KeyboardInterrupt:
print("\nDisconnecting...")
client.loop_stop()
client.disconnect()846.5 Summary
This chapter covered the fundamentals of ESP32 Wi-Fi implementation:
- Station Mode Configuration: Connecting ESP32 to existing Wi-Fi networks with connection handling, timeout management, and auto-reconnect logic
- Access Point Mode: Creating ESP32-hosted Wi-Fi networks for device configuration, local control, and mesh networking
- Network Scanning: Discovering available networks with SSID, RSSI, channel, and security information for network selection and site surveys
- SmartConfig Provisioning: Wirelessly configuring Wi-Fi credentials without hardcoding them in firmware
- Raspberry Pi Configuration: Using nmcli and wpa_supplicant for Linux-based IoT Wi-Fi setup
846.6 Whatβs Next
The next chapter covers Wi-Fi Power Optimization, exploring power-saving modes, deep sleep implementations, and battery life calculations for battery-powered Wi-Fi IoT devices.