WIFI AP Mode Experiment

1. WIFI AP Mode Overview

WiFi AP (Access Point, hotspot mode) lets the ESP32-S3 turn itself into a wireless router/hotspot; other devices (phones, computers, another ESP32) can search for and connect to this hotspot to achieve LAN communication.

AP mode has irreplaceable application value in the IoT field. First, it is the foundation of provisioning technology — when a device is first deployed and no WiFi network is available, the device first runs in AP mode, the user connects their phone to the hotspot and sends the router password to the device through a web page or App, and the device then switches to STA mode to go online (this is the first step of the SmartConfig / Web provisioning process). Second, in no-router scenarios (field work, site inspections, temporary exhibitions), AP mode lets users directly connect to devices point-to-point for parameter configuration, status viewing, and firmware upgrades without depending on any network infrastructure. In addition, AP mode is also widely used in LAN multi-user collaboration scenarios — multiple phones or computers connect to the same ESP32-S3 hotspot for local chat, file sharing, multiplayer games, and other LAN applications.

This experiment configures the ESP32-S3 in AP mode; a phone or computer can view the connection status after connecting.

Typical application scenarios:

In AP mode the ESP32-S3 supports about 4~8 devices connecting simultaneously at most.

2. Core Concepts

2.1 How AP Mode Works

              ┌──────────┐
Phone  ─────→ |          |
PC  ────────→ | ESP32-S3 |  (no Internet, pure LAN)
Tablet  ────→ | (AP)     |
              └──────────┘

The ESP32-S3 creates its own hotspot and broadcasts the SSID; other devices scan and connect. The ESP32-S3 acts as a DHCP server to assign IPs to clients. In AP mode, the ESP32-S3's default IP is usually 192.168.4.1.

2.2 Configuration Parameters

2.3 Core API

​x
import network
​
ap = network.WLAN(network.AP_IF)           # create AP interface
ap.active(True)                             # activate
ap.config(essid="ESP32-AP",                # set SSID + password
          password="12345678",
          authmode=network.AUTH_WPA_WPA2_PSK)
ip, _, _, _ = ap.ifconfig()                # get AP's own IP
ap.status('stations')                       # get connected clients
ap.active(False)                            # deactivate

3. Hardware Dependencies

The ESP32-S3 has a built-in 2.4 GHz WiFi module, no external hardware needed.

4. Project Architecture and Flow

xxxxxxxxxx
Script execution (single-file .py)
  |
  |- create AP interface -> set SSID/password/encryption
  |- wait for AP activation -> print IP
  |
  |- while True:
       |- poll the list of connected clients
       |- detect new connection -> print MAC address
       |- detect disconnect -> print MAC address
       |- sleep(1s)

5. Source Code Explained

Full source code: Source Code -> MicroPython -> 4.Network Protocols -> WiFi_AP -> WiFi_AP.py

5.1 Configuration and Activation

AP_IF interface -> active(True) -> config(ssid, password, authmode) sets the hotspot parameters -> wait for activation to complete.

xxxxxxxxxx
AP_SSID     = 'ESP32_AP'                # AP SSID
AP_PASSWORD = '12345678'                    # AP password (min 8 chars)
​
def main():
    ap = network.WLAN(network.AP_IF)        # create AP interface
    ap.active(True)                          # activate
    ap.config(essid=AP_SSID, password=AP_PASSWORD,
              authmode=network.AUTH_WPA_WPA2_PSK)  # WPA2 encryption
​
    while not ap.active():
        time.sleep_ms(100)                   # wait for activation
​
    ip, _, _, _ = ap.ifconfig()
    print('WiFi AP ready')
    print('  SSID     :', AP_SSID)
    print('  IP       :', ip)

5.2 Client Connection Monitoring

status('stations') gets the MAC list of connected devices; comparing two consecutive snapshots implements connect/disconnect detection.

xxxxxxxxxx
def mac_str(mac):
    """bytearray -> readable string"""
    return '%02x:%02x:%02x:%02x:%02x:%02x' % (mac[0], mac[1], mac[2],
                                                mac[3], mac[4], mac[5])
​
prev = []
while True:
    cur = [t[0] for t in ap.status('stations')]  # current clients
​
    for mac in cur:                                # new connections
        if mac not in prev:
            print('Connected   :', mac_str(mac))
​
    for mac in prev:                               # disconnected
        if mac not in cur:
            print('Disconnected:', mac_str(mac))
​
    prev = cur
    time.sleep(1)                                  # 1s polling interval

status('stations') returns a list of (MAC, ...) tuples of connected devices; connect/disconnect detection is implemented by comparing two consecutive snapshots.

6. Operating Procedures

6.1 Flashing and Running

Thonny IDE steps: See MicroPython -> 1. Before Development -> 3.Thonny IDE.

Thonny IDE flashing steps: See the MicroPython -> 1. Before Development -> 3.Thonny IDE

1. Open WiFi_AP.py in Thonny IDE and click Run
2. Open the WiFi settings on your phone and search for ESP32_AP
3. Enter the password 12345678 to connect

6.2 Expected Results

After the ESP32-S3 creates the hotspot, the phone can find and connect to it. The serial port prints client connect/disconnect logs.

6.3 Serial Output Example

xxxxxxxxxx
WiFi AP ready
  SSID     : ESP32_AP
  IP       : 192.168.4.1
Connected   : aa:bb:cc:dd:ee:ff
Disconnected: aa:bb:cc:dd:ee:ff

Hotspot is on, phone connects successfully

Phone disconnects

6.4 Verification Methods

7. Common Problems