Wifi

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TODO: {{#todo: Complete (10.20.2015-14:23->JJ+);(10.20.2015-13:43->JJ+);(10.23.2015-11:50->MD-);(10.26.2015-16:50->JJ+);(10.27.2015-15:30->JJ+); (10.28.2015-15:05->JJ+);(10.28.2015-16:35->MD-); (11.2.2015-14:45->JJ+); (11.3.2015-19:35->MD-); (11.4.2015-14:40->JJ+);(11.05.2015-15:40->MD+); (11.10.2015-15:05->JJ-);(11.13.2015-14:00->MG+);(11.13.2015-14:44->KY+)|Jeffrey Jung|OE 5.0,Complete,JJ,MD,MG}}

This guide will illustrate how to set up and connect to a wireless network using the ThinkPenguin Wireless N USB Adapter for GNU/Linux and the built-in WiFi on the SoM-200GS carrier.


Background

While many boards from EMAC are not natively designed to connect to wireless networks, most of these systems do have USB ports. Using a USB wireless network adapter, a system can be equipped with wireless networking capability. Such a USB adapter can be ordered by contacting the sales team here at EMAC. Request the product by its part number, PER-USB-00005-R.


This page describes the actions needed to connect to a wireless network using either a wireless network USB adapter, or the built-in Wi-Fi found on EMAC products like the SoM-200GS carrier. We chose to use the ThinkPenguin USB adapter for this page because it is well supported by the Linux kernel.


General Information

Set Up

Before the device can be connected to the network, some additional software may need to be installed. Boards with Wi-Fi built in should already have the proper software and drivers to support connecting to a wireless network. If so, skip to the Wireless Networking section.

  1. In order to obtain the new packages, connect the system to a physical network.

  2. This process requires modifying some system files, so start by enabling read and write permissions to the filesystem.

    root@ipac9x25:~# mount -o remount,rw /

  3. A check for any updates to the package list is typically a good practice before installing new software. Use the opkg manager to update the package list.

    root@ipac9x25:~# opkg update

  4. One of the best tools to establish the connection to wireless networks is the wpa-supplicant package. This supplicant will allow the system to make connections to WPA and WPA2 protected networks. Install this package with the opkg tool.

    root@ipac9x25:~# opkg install wpa-supplicant

  5. Install the wireless firmware

    • If using the USB adapter, the appropriate firmware may need to be installed. The ThinkPenguin USB adapter requires the installation of the linux-firmware-ath9k package.

    root@ipac9x25:~# opkg install linux-firmware-ath9k

    • The firmware package for the built-in Wi-Fi on EMAC's 200GS carrier board is linux-firmware-sd8787.

    root@som9x25:~# opkg install linux-firmware-sd8787

  6. Independent of whether you're connecting with an adapter or using built-in capabilities, the iw and wireless-tools packages will complete the needed software to get a connection started.

    root@ipac9x25:~# opgk install iw
    root@ipac9x25:~# opkg install wireless-tools

All the necessary software required to make the wireless connection has now been obtained. The USB adapter can now be plugged in and will be recognized by the operating system.

Wireless Networking

Using the packages that have just been installed, the system can be connected to the wireless network.

  1. Changes to some configuration files will be necessary, so remount the root filesystem with read and write permissions.

    root@ipac9x25:~# mount -o remount,rw /

  2. Wireless networks can be found using the scan option of iw.

    root@ipac9x25:~# iw dev wlan0 scan
    A detailed list of the nearby networks will be printed out to the terminal. To identify the SSIDs and respective signal strengths of the network(s) more easily, pipe the output of the iw scan command through grep to scan for the keywords "SSID" or "signal". The closer the value of the signal strength is to 0, the stronger the connection.
    root@ipac9x25:~# iw dev wlan0 scan | grep SSID
    SSID: EMAC-A
    root@ipac9x25:~# iw dev wlan0 scan | grep signal
    signal: -78.00dBm
    root@ipac9x25:~#


    The /etc/wpa_supplicant.conf file will need to be modified to provide the necessary connection information, the details of which depend upon the type of encryption used for the wireless network.

  3. For an open network, uncomment the following lines in /etc/wpa_supplicant.conf and fill in the correct SSID for the network to which the machine should connect. 

    ###open network
#network={
#      ssid="SSID"
#      scan_ssid=1
#       key_mgmt=NONE
#}

  4. Networks protected by either WEP or WPA2 encryption will need a pre-shared key (PSK), which is generated for the specific network and its password. To get the PSK, use wpa_passphrase with the SSID and password for the desired network as arguments. Copy the last psk line and paste into the /etc/wpa_supplicant.conf file.

    root@ipac9x25:~# wpa_passphrase SSID Password

    network={

    ssid="SSID"
    #psk="Password"
    psk=b99d2c0fb66194f93ad52b71051e1095dc76e12529321334b3feb18332608eb7

    }

  5. The contents of the /etc/wpa_supplicant.conf should now look similar to the following:

    root@ipac9x25:~# cat /etc/wpa_supplicant.conf

    network={

    ssid="SSID"
    proto=WPA
    key_mgmt=WPA-PSK
    psk=b99d2c0fb66194f93ad52b71051e1095dc76e12529321334b3feb18332608eb7

    }

    root@ipac9x25:~#


  6. The root@som9x25:~# /etc/init.d/wpa_supplicant start command will attempt to establish a connection with the network.

    As the command is running, watch the terminal output for the status of the connection. A connection has been established when output stops and the last line reads:
    IPv6 ADDRCONF(NETDEV_CHANGE):wlan0: link becomes ready
    A connection has failed if output to the terminal continues and the following line is seen repeatedly:
    IPv6: ADDRCONF(NETDEV_UP):wlan0: link is not ready
    Successful connection (waiting a full minute to ensure output to the terminal stopped);
    root@ipac9x25:~# /etc/init.d/wpa-supplicant start

    Successfully initialized wpa_supplicant
    rfkill: Cannot open RFKILL control device

    root@ipac9x25:~# wlan0: authenticate with 1c:7e:e5:40:10:fd

    wlan0: send auth to 1c:7e:e5:40:10:fd (try 1/3)
    wlan0: send auth to 1c:7e:e5:40:10:fd (try 2/3)
    wlan0: authenticated
    wlan0: associating with AP with corrupt beacon
    wlan0: associate with 1c:7e:e5:40:10:fd (try 1/3)
    wlan0: RX AssocResp from 1c:7e:e5:40:10:fd (capab=0x431 status=0 aid=6)
    wlan0: associated
    IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

    Failed connection (waiting more than a minute as output continues to print to the terminal). The repeated lines indicate an issue establishing the connection.
    root@ipac9x25:~# /etc/init.d/wpa-supplicant start

    Successfully initialized wpa_supplicant IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready

    root@ipac9x25:~# IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

    cfg80211: Calling CRDA to update world regulatory domain
    IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
    cfg80211: Calling CRDA to update world regulatory domain
    IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
    IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
    cfg80211: Calling CRDA to update world regulatory domain
    IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
    IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
    cfg80211: Calling CRDA to update world regulatory domain
    IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
    IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
    cfg80211: Calling CRDA to update world regulatory domain
    IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
    IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
    cfg80211: Calling CRDA to update world regulatory domain
    IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
    IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
    cfg80211: Calling CRDA to update world regulatory domain
    IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready

    A failed connection is likely the result of an improper password. Use wpa_passphrase to make sure you have the right psk for the password.

  7. The ifconfig command will be used to determine that the device is wirelessly connected to the network. Look to see that wlan0 has an IP address.

    wlan0 Link encap:Ethernet HWaddr A8:54:B2:42:89:8D
    inet addr:10.0.4.148 Bcast:10.0.255.255 Mask:255.255.0.0
    UP BROADCAST RUNNING MULTICAST MTU:1500 METRIC:1
    RX packets:3395 errors:0 dropped:6 overruns:0 frame:0
    TX packets:60 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:1000
    RX bytes:346619 (338.4 KiB) TX bytes:6318 (6.1 Kib)

  8. Disconnect any physical connections from the system and ping to www.emacinc.com to verify that the system can wirelessly connect to the Internet.

    root@ipac9x25:~# ping -c 3 www.emacinc.com

    PING www.emacinc.com (172.16.0.10): 56 data bytes 64 bytes from 172.16.0.10: seq=0 ttl=63 time=1.910 ms 64 bytes from 172.16.0.10: seq=1 ttl=63 time=1.748 ms 64 bytes from 172.16.0.10: seq=2 ttl=63 time=2.061 ms

    --- www.emacinc.com ping statistics --- 3 packets transmitted, 3 packets received, 0% packet loss round-trip min/avg/max = 1.748/1.906/2.061 ms

    root@ipac9x25:~#


Troubleshooting

If your come across any issues communicating though the network, try these suggestions as starting points to resolve the problem(s).

  • View the /etc/resolv.conf file to view the DNS servers provided from the DHCP server.
  • Inspect the routing table using the route command, as shown here:
root@ipac9x25:~# route -n

Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 10.0.2.1 0.0.0.0 UG 0 0 0 eth0 10.0.0.0 0.0.0.0 255.255.0.0 U 1 0 0 eth0

root@ipac9x25:~#

Conclusion

After connecting to a network the first time, the system will be able to connect to the same network when rebooted or powered on. Connecting to a new network will require going through the procedures set out under the Wireless Networking section to revise the network settings.


This page walked the reader through the procedure to connect a machine to a wireless network via a USB Wifi adapter or built-in wireless, and the process to acquire the necessary software tools to make the connection for the first time. While there are plenty of USB wireless adapters available for sale, we used an adapter intended for use on Linux machines with a driver supported by EMAC OE Linux. Other USB wireless adapters may be used to connect EMAC devices to wireless networks, but they will often face issues with driver support or other compatibility issues. Requests to purchase the adapter should be sent to sales@emacinc.com; please include a reference to the EPN, PER-USB-00005-R, when sending a request to purchase this adapter.


Further Information

Where to Go Next
Pages with Related Content
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