04 WIFI

1 WIFI Module Overview

GM-3568JHF development board integrates RTL8723DU wireless network module, providing complete IEEE 802.11 b/g/n wireless network connection function. The module connects to the main control chip via USB interface, supporting 2.4GHz frequency band wireless communication, providing flexible wireless network access capabilities for the development board.

1.1 RTL8723DU Module Technical Specifications

Parameter	Specification
Chip Model	Realtek RTL8723DU
Interface Type	USB 2.0
Wireless Standard	IEEE 802.11 b/g/n
Working Frequency	2.4GHz (2.412~2.484GHz)
Transmission Rate	Max 150Mbps (802.11n)
Modulation	OFDM, CCK, BPSK, QPSK, 16-QAM, 64-QAM
Antenna Configuration	1T1R (One Transmit One Receive)
Transmit Power	Max 20dBm
Receive Sensitivity	-70dBm @ 150Mbps
Encryption Support	WEP, WPA/WPA2-PSK, WPA/WPA2-Enterprise

1.2 Performance Indicators

Mode	Max Rate	Typical Range	Power Consumption
802.11b	11Mbps	100m	Low
802.11g	54Mbps	50m	Medium
802.11n	150Mbps	30m	Medium High

2 WIFI Connection Configuration

The development board uses the RTL8723DU module, and the system has pre-adapted the WIFI driver and related software components.

2.1 Connecting to WIFI

As shown in the figure, find the network icon in the upper right corner of the system and click to connect to WIFI. WIFI

Use ifconfig command to view IP address and other information.

root@linaro-alip:/# ifconfig
···
wlx78228877b4a5: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.137.149  netmask 255.255.255.0  broadcast 192.168.137.255
        inet6 fe80::d175:3cd1:73ca:ecc8  prefixlen 64  scopeid 0x20<link>
        ether 78:22:88:77:b4:a5  txqueuelen 1000  (Ethernet)
        RX packets 69  bytes 954099 (931.7 KiB)
        RX errors 0  dropped 143  overruns 0  frame 0
        TX packets 72  bytes 116372 (113.6 KiB)
        TX errors 0  dropped 23 overruns 0  carrier 0  collisions 0

2.2 Connectivity Test

Execute the following command to check the obtained IP address, and test whether the communication between the development board and the PC is normal via the ping command. 192.168.49.85 is the actual IP address of the PC. Please ensure that the development board and the PC are in the same local area network.

root@linaro-alip:/# ping 192.168.49.85 -I wlx78228877b4a5 -c 8
ping 192.168.49.85 -I wlx78228877b4a5 -c 8
PING 192.168.49.85 (192.168.49.85) from 192.168.137.149 wlx78228877b4a5: 56(84) bytes of data.
64 bytes from 192.168.49.85: icmp_seq=1 ttl=127 time=5.14 ms
64 bytes from 192.168.49.85: icmp_seq=2 ttl=127 time=3.66 ms
64 bytes from 192.168.49.85: icmp_seq=3 ttl=127 time=2.83 ms
64 bytes from 192.168.49.85: icmp_seq=4 ttl=127 time=2.81 ms
64 bytes from 192.168.49.85: icmp_seq=5 ttl=127 time=9.44 ms
64 bytes from 192.168.49.85: icmp_seq=6 ttl=127 time=2.77 ms
64 bytes from 192.168.49.85: icmp_seq=7 ttl=127 time=3.46 ms
64 bytes from 192.168.49.85: icmp_seq=8 ttl=127 time=3.09 ms

--- 192.168.49.85 ping statistics ---
8 packets transmitted, 8 received, 0% packet loss, time 7011ms
rtt min/avg/max/mdev = 2.771/4.150/9.442/2.128 ms

2.3 TCP Bandwidth Test

Use the iperf3 tool to test the network communication bandwidth between the development board and the PC as follows.

Server Side

Connect the development board to the Internet and install the iperf3 tool, executing the following commands:

root@linaro-alip:/# sudo apt update
root@linaro-alip:/# sudo apt install iperf3

The development board acts as the server, executing the following command:

root@linaro-alip:/# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------

Client Side

The iperf3 tool for Windows can be obtained from the test toolkit.

Open PowerShell in Windows system, enter the path where the iperf3 tool is located. Use Windows as the client to send data by executing the following command:

.\iperf3.exe -c 192.168.137.149 // 192.168.137.149 is the server IP address

2.4 Test Results

Server Side

root@linaro-alip:/# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Accepted connection from 192.168.137.1, port 65396
[  5] local 192.168.137.149 port 5201 connected to 192.168.137.1 port 65397
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  4.88 MBytes  40.9 Mbits/sec
[  5]   1.00-2.00   sec  5.40 MBytes  45.3 Mbits/sec
[  5]   2.00-3.00   sec  5.22 MBytes  43.8 Mbits/sec
[  5]   3.00-4.00   sec  5.36 MBytes  45.0 Mbits/sec
[  5]   4.00-5.00   sec  5.14 MBytes  43.1 Mbits/sec
[  5]   5.00-6.00   sec  5.22 MBytes  43.8 Mbits/sec
[  5]   6.00-7.00   sec  5.40 MBytes  45.3 Mbits/sec
[  5]   7.00-8.00   sec  5.12 MBytes  43.0 Mbits/sec
[  5]   8.00-9.00   sec  5.38 MBytes  45.1 Mbits/sec
[  5]   9.00-10.00  sec  5.24 MBytes  43.9 Mbits/sec
[  5]  10.00-10.05  sec   266 KBytes  45.9 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-10.05  sec  52.6 MBytes  43.9 Mbits/sec                  receiver
-----------------------------------------------------------

Client Side

WIFI_2

3 Command Line WIFI Configuration

3.1 Connecting WIFI with wpa_supplicant

1) Scanning for Available Networks

# Enable WIFI interface
sudo ifconfig wlx78228877b4a5 up

# Scan available WIFI networks
sudo iwlist wlx78228877b4a5 scan | grep ESSID

# Or use iw command
sudo iw dev wlx78228877b4a5 scan | grep SSID

2) Creating wpa_supplicant Configuration File

# Create configuration file
sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

# Add the following content
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
update_config=1
country=CN

# WPA/WPA2-PSK Network Configuration
network={
    ssid="YourWiFiName"
    psk="YourPassword"
    key_mgmt=WPA-PSK
    priority=1
}

# Open Network Configuration
network={
    ssid="OpenWiFi"
    key_mgmt=NONE
    priority=2
}

# WEP Network Configuration
network={
    ssid="WEPNetwork"
    wep_key0="your_wep_key"
    key_mgmt=NONE
    wep_tx_keyidx=0
}

3) Connecting to WIFI Network

# Start wpa_supplicant
sudo wpa_supplicant -B -i wlx78228877b4a5 -c /etc/wpa_supplicant/wpa_supplicant.conf

# Obtain IP Address
sudo dhclient wlx78228877b4a5

# Check Connection Status
wpa_cli -i wlx78228877b4a5 status

3.2 Managing WIFI with NetworkManager

Command Line Tool nmcli

# View WIFI Status
nmcli radio wifi

# Scan WIFI Networks
nmcli dev wifi list

# Connect to WIFI Network
nmcli dev wifi connect "SSID" password "PASSWORD"

# View Saved Connections
nmcli connection show

# Disconnect WIFI
nmcli dev disconnect wlx78228877b4a5

# Delete Saved Connection
nmcli connection delete "SSID"

4 WIFI Hotspot Mode (AP Mode)

4.1 Installing hostapd

sudo apt-get update
sudo apt-get install hostapd dnsmasq

4.2 Configuring hostapd

# Create hostapd configuration file
sudo nano /etc/hostapd/hostapd.conf

# Add the following content
interface=wlx78228877b4a5
driver=nl80211
ssid=GM-3568JHF-AP
hw_mode=g
channel=7
wmm_enabled=0
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=12345678
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

4.3 Configuring DHCP Service

# Backup original configuration
sudo cp /etc/dnsmasq.conf /etc/dnsmasq.conf.backup

# Edit dnsmasq configuration
sudo nano /etc/dnsmasq.conf

# Add the following content
interface=wlx78228877b4a5
dhcp-range=192.168.4.2,192.168.4.20,255.255.255.0,24h

4.4 Configuring Network Interface

# Set Static IP
sudo ifconfig wlx78228877b4a5 192.168.4.1 netmask 255.255.255.0

# Enable IP Forwarding
echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward

# Configure NAT Rules
sudo iptables -t nat -A POSTROUTING -o end0 -j MASQUERADE
sudo iptables -A FORWARD -i end0 -o wlx78228877b4a5 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i wlx78228877b4a5 -o end0 -j ACCEPT

4.5 Starting Hotspot Service

# Start hostapd
sudo hostapd /etc/hostapd/hostapd.conf &

# Start dnsmasq
sudo systemctl start dnsmasq

# Check Service Status
sudo systemctl status hostapd
sudo systemctl status dnsmasq

5 Troubleshooting

1) WIFI Module Not Recognized

Check Steps:

# Check USB Device
lsusb | grep Realtek

# Check Kernel Module
lsmod | grep rtl

# Manually Load Driver
sudo modprobe rtl8xxxu

# Check Firmware Files
ls /lib/firmware/rtlwifi/

2) Unable to Connect to WIFI Network

Possible Causes and Solutions:

# Check Network Interface Status
ip link show wlx78228877b4a5

# Restart Network Interface
sudo ifconfig wlx78228877b4a5 down
sudo ifconfig wlx78228877b4a5 up

# Check wpa_supplicant Log
sudo journalctl -u wpa_supplicant

# Reconfigure Network
sudo wpa_cli -i wlx78228877b4a5 reconfigure

3) Weak Signal or Unstable Connection

Optimization Suggestions:

# Check Signal Strength
iwconfig wlx78228877b4a5 | grep "Signal level"

# Scan Channel Usage
sudo iwlist wlx78228877b4a5 scan | grep Frequency

# Change Channel (AP Mode)
sudo iwconfig wlx78228877b4a5 channel 6

# Adjust Transmit Power
sudo iwconfig wlx78228877b4a5 txpower 20

4) Slow Network Speed

Diagnosis and Optimization:

# Check Current Connection Rate
iwconfig wlx78228877b4a5 | grep "Bit Rate"

# Check Network Congestion
ping -c 10 8.8.8.8

# Test Bandwidth with iperf3
iperf3 -c speedtest.server.com

# Optimize TCP Window Size
echo 'net.core.rmem_max = 16777216' >> /etc/sysctl.conf
echo 'net.core.wmem_max = 16777216' >> /etc/sysctl.conf

5) Hotspot Mode Issues

Common Issues Resolution:

# Check hostapd Status
sudo systemctl status hostapd

# View hostapd Log
sudo journalctl -u hostapd

# Check Firewall Settings
sudo iptables -L

# Restart Related Services
sudo systemctl restart hostapd
sudo systemctl restart dnsmasq