pycom-documentation/content/tutorials/networks/wlan.md

title, aliases

title	aliases
WiFi Examples	tutorials/networks/wlan.html tutorials/networks/wlan.md chapter/tutorials/networks/wlan

The WLAN (WiFi) is a system feature of all Pycom devices, therefore it is enabled by default.

Note: Changing the WLAN settings while using the Telnet server might break the wireless connection to the device permanently. Please use caution or a USB cable :)

On this page, we cover:

1. Connecting to the Device
2. Connecting to a Router

Note: Generally, code in either sections is applicable to both WLAN modes.

Connecting to the Device

Using the WLAN class from network, you can change the name (SSID) and security settings (auth) of the access point.

from network import WLAN
wlan = WLAN(mode=WLAN.AP)

wlan.init(ssid="hello world", auth=None)
#use the line below to apply a password
#wlan.init(ssid="hi", auth=(WLAN.WPA2, "eightletters"))
print(wlan.ifconfig(id=1)) #id =1 signifies the AP interface

The device will not be able to access the internet, but you will be able to run a simple webserver. By default, the ip address will be configured to 192.168.4.1.

Connecting to a Router

The WLAN network class always boots in WLAN.AP mode; to connect it to an existing network, the WiFi class must be configured as a station:

from network import WLAN
import machine
wlan = WLAN(mode=WLAN.STA)

wlan.connect(ssid='ssid', auth=(WLAN,WPA2, 'password'))
while not wlan.isconnected():
    machine.idle()
print("WiFi connected succesfully")
print(wlan.ifconfig())

Note: If the device hangs in the while loop, probably your network is out of reach, or you made a mistake entering your WiFi credentials.

Scan

If you are not always in reach of your network (maybe you have a moving device), you can also scan for the network using the example below.

from network import WLAN
import machine
wlan = WLAN(mode=WLAN.STA)

nets = wlan.scan()
for net in nets:
    if net.ssid == 'mywifi':
        print('Network found!')
        wlan.connect(net.ssid, auth=(net.sec, 'mywifikey'), timeout=5000)
        while not wlan.isconnected():
            machine.idle() # save power while waiting
        print('WLAN connection succeeded!')
        break

Assigning a Static IP Address at Boot Up

If you want to connect your device to a wireless router, and access it from a telnet terminal, you can use the following example to assign a fixed ip address (192.168.1.10, check with your wifi network for possibilities), use the following script as /boot.py:

import machine
from network import WLAN
wlan = WLAN() # get current object, without changing the mode

if machine.reset_cause() != machine.SOFT_RESET: #do not reset the wireless connection on soft reset.
    wlan.init(mode=WLAN.STA)
    # configuration below MUST match your home router settings!!
    wlan.ifconfig(config=('192.168.178.107', '255.255.255.0', '192.168.1.10', '8.8.8.8')) # (ip, subnet_mask, gateway, DNS_server)

if not wlan.isconnected():
    # change the line below to match your network ssid, security and password
    wlan.connect('mywifi', auth=(WLAN.WPA2, 'mywifikey'), timeout=5000)
    while not wlan.isconnected():
        machine.idle() # save power while waiting

{{% hint style="info" %}} Notice how we check for the reset cause and the connection status, this is crucial in order to be able to soft reset the LoPy during a telnet session without breaking the connection. {{% /hint %}}

Multiple Networks using a Static IP Address

The following script holds a list with nets and an optional list of wlan_config to set a fixed IP

import os
import machine

uart = machine.UART(0, 115200)
os.dupterm(uart)

known_nets = {
    '<net>': {'pwd': '<password>'},
    '<net>': {'pwd': '<password>', 
    'wlan_config':  ('10.0.0.114', '255.255.0.0', '10.0.0.1', '10.0.0.1')}, # (ip, subnet_mask, gateway, DNS_server)
}

if machine.reset_cause() != machine.SOFT_RESET:
    from network import WLAN
    wl = WLAN()
    wl.mode(WLAN.STA)
    original_ssid = wl.ssid()
    original_auth = wl.auth()

    print("Scanning for known wifi nets")
    available_nets = wl.scan()
    nets = frozenset([e.ssid for e in available_nets])

    known_nets_names = frozenset([key for key in known_nets])
    net_to_use = list(nets & known_nets_names)
    try:
        net_to_use = net_to_use[0]
        net_properties = known_nets[net_to_use]
        pwd = net_properties['pwd']
        sec = [e.sec for e in available_nets if e.ssid == net_to_use][0]
        if 'wlan_config' in net_properties:
            wl.ifconfig(config=net_properties['wlan_config'])
        wl.connect(net_to_use, (sec, pwd), timeout=10000)
        while not wl.isconnected():
            machine.idle() # save power while waiting
        print("Connected to "+net_to_use+" with IP address:" + wl.ifconfig()[0])

    except Exception as e:
        print("Failed to connect to any known network, going into AP mode")
        wl.init(mode=WLAN.AP, ssid=original_ssid, auth=original_auth, channel=6, antenna=WLAN.INT_ANT)

Connecting to a WPA2-Enterprise network

• Connecting with EAP-TLS: Before connecting, obtain and copy the public and private keys to the device, e.g. under location /flash/cert. If it is required to validate the server's public key, an appropriate CA certificate (chain) must also be provided.

from network import WLAN

wlan = WLAN(mode=WLAN.STA)
wlan.connect(ssid='mywifi', auth=(WLAN.WPA2_ENT,), identity='myidentity', ca_certs='/flash/cert/ca.pem', keyfile='/flash/cert/client.key', certfile='/flash/cert/client.crt')

• Connecting with EAP-PEAP or EAP-TTLS: In case of EAP-PEAP (or EAP-TTLS), the client key and certificate are not necessary, only a username and password pair. If it is required to validate the server's public key, an appropriate CA certificate (chain) must also be provided.

from network import WLAN

wlan = WLAN(mode=WLAN.STA)
wlan.connect(ssid='mywifi', auth=(WLAN.WPA2_ENT, 'username', 'password'), identity='myidentity', ca_certs='/flash/cert/ca.pem')