（二）为树莓派配置无线网卡

Wifi配置

我的Wifi配置基本上是跟着这个教程来的，下面将过程简述，并解释每个命令/语句的作用。

1、检查USB无线网卡是否已经正确识别

将无线USB网卡插入树莓派后启动树莓派，比较不建议热插拔，因为插入的一瞬间会有比较高的电流，如果电源输出不够可能导致树莓派重启。用自己的方法进入shell界面后输入命令：

 lsusb

如果树莓派已经正常识别，在显示类似于如下的信息中可以看到你的USB无线网卡设备ID和芯片型号

 Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. SMSC9512/9514 Fast Ethernet Adapter
 Bus 001 Device 004: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter

以我的EDUP为例，使用的是Realtek RTL8188CUS的芯片。

最新的raspbian已经有了wifi必要的包，直接插上就可以用了。不过最好还是可以看看iwconfig确认一下，输入

 iwconfig

显示如下：

 wlan0     IEEE 802.11bgn  ESSID:"BabyBeaR_du"  Nickname:""
           Mode:Managed  Frequency:2.412 GHz  Access Point: BC:96:80:19:FD:98
           Bit Rate:150 Mb/s   Sensitivity:0/0
           Retry:off   RTS thr:off   Fragment thr:off
           Power Management:off
           Link Quality=100/100  Signal level=100/100  Noise level=0/100
           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
           Tx excessive retries:0  Invalid misc:0   Missed beacon:0


 lo        no wireless extensions.


 eth0      no wireless extensions.

如果出现了wlan0，那说明网卡已经正常工作了。（这里的示例是已经用usb无线网卡连接上网络了，所以会显示ESSID。）如果这里的显示不正常，请安装连接wifi必要的包

 sudo apt-get install wireless-tools wpasupplicant firmware-realtek

2、设置wifi

输入如下命令可以搜索附近所有可连接的Wifi AP：

 iwlist wlan0 scan

 wlan0     Scan completed :
           Cell 01 - Address: 00:1D:7E:FB:BA:F1
                     ESSID:"tociek-net"
                     Protocol:IEEE 802.11bg
                     Mode:Master
                     Frequency:2.437 GHz (Channel 6)
                     Encryption key:on
                     Bit Rates:54 Mb/s
                     Extra:wpa_ie=dd1c0050f20101000050f20202000050f2040050f20201000050f2020000
                     IE: WPA Version 1
                         Group Cipher : TKIP
                         Pairwise Ciphers (2) : CCMP TKIP
                         Authentication Suites (1) : PSK
                     Extra:rsn_ie=30180100000fac020200000fac04000fac020100000fac020000
                     IE: IEEE 802.11i/WPA2 Version 1
                         Group Cipher : TKIP
                         Pairwise Ciphers (2) : CCMP TKIP
                         Authentication Suites (1) : PSK
                     Quality=100/100  Signal level=100/100
           Cell 02 - Address: 00:21:27:E9:EA:00
                     ESSID:"Jacek"
                     Protocol:IEEE 802.11bg
                     Mode:Master
                     Frequency:2.437 GHz (Channel 6)
                     Encryption key:on
                     Bit Rates:54 Mb/s
                     Extra:wpa_ie=dd1a0050f20101000050f20202000050f2020050f20401000050f202
                     IE: WPA Version 1
                         Group Cipher : TKIP
                         Pairwise Ciphers (2) : TKIP CCMP
                         Authentication Suites (1) : PSK
                     Extra:rsn_ie=30180100000fac020200000fac02000fac040100000fac020100
                     IE: IEEE 802.11i/WPA2 Version 1
                         Group Cipher : TKIP
                         Pairwise Ciphers (2) : TKIP CCMP
                         Authentication Suites (1) : PSK
                        Preauthentication Supported
                     Quality=61/100  Signal level=54/100

（这段返回信息是 从这个帖子 里复制的，我这边的wifi比较多，返回信息太长了，所以就不贴过来了）

值得注意的是，在windows下使用ICS建立的虚拟无线AP是无法被树莓派检测到的，具体原因不清楚，有时间了再研究。如这篇文章中我说过的，我这里没有wlan环境，之前也是一直用的windows建立的软AP。因此我把之前提到的那个小度WIFI插上了，还真能连上。。。

确定树莓派可以检测到你建立的wifiap之后，按照如下方法配置

使用如下命令获得wifi设置：

 wpa_passphrase SSID名称 密码

回显如下

 network={
         ssid="SSID名称"
         #psk="密码"
         psk=4b7084a26fea96aaf67518820cc1151fb8f47c5fc0674cd6e877a2ecd70b596e
 }

复制这段回显并保存到自己的配置文件中

 sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

然后配置/etc/network/interfaces

 sudo nano /etc/network/interfaces

如果自动获得IP地址，配置内容如下：

 allow-hotplug wlan0
 auto wlan0
 iface wlan0 inet dhcp
 pre-up wpa_supplicant -B w -D wext -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf
 post-down killall -q wpa_supplicant

如果设置固定IP地址，配置内容如下：

 allow-hotplug wlan0
 auto wlan0
 iface wlan0 inet manual
   address 192.168.1.137
   netmask 255.255.255.0
   network 192.168.1.0
   broadcast 192.168.1.255
   gateway 192.168.1.1
 wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
 iface default inet dhcp

无线wifi设置静态ip时，要将
allow-hotplug wlan0  
auto wlan0  
iface wlan0 inet static 
wpa-ssid 用户名
wpa-psk  密码
  address 192.168.1.137  
  netmask 255.255.255.0  
  network 192.168.1.0  
  broadcast 192.168.1.255  
  gateway 192.168.1.1  

iface default inet dhcp

连接网络

 sudo ifup wlan0

 rfkill: Cannot open RFKILL control device
 ioctl[SIOCSIWAP]: Operation not permitted
 ioctl[SIOCSIWENCODEEXT]: Invalid argument
 ioctl[SIOCSIWENCODEEXT]: Invalid argument
 Internet Systems Consortium DHCP Client 4.2.2
 Copyright 2004-2011 Internet Systems Consortium.
 All rights reserved.
 For info, please visit https://www.isc.org/software/dhcp/

 Listening on LPF/wlan0/a0:f3:c1:08:21:ac
 Sending on   LPF/wlan0/a0:f3:c1:08:21:ac
 Sending on   Socket/fallback
 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 7
 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 14
 DHCPREQUEST on wlan0 to 255.255.255.255 port 67
 DHCPOFFER from 192.168.1.1
 DHCPACK from 192.168.1.1
 Reloading /etc/samba/smb.conf: smbd only.
 bound to 192.168.1.137 -- renewal in 39240 seconds.

关闭连接使用如下命令

 pi@raspbmc:~$ sudo ifdown wlan0

 Internet Systems Consortium DHCP Client 4.2.2
 Copyright 2004-2011 Internet Systems Consortium.
 All rights reserved.
 For info, please visit https://www.isc.org/software/dhcp/

 Listening on LPF/wlan0/a0:f3:c1:08:21:ac
 Sending on   LPF/wlan0/a0:f3:c1:08:21:ac
 Sending on   Socket/fallback
 DHCPRELEASE on wlan0 to 192.168.1.1 port 67
 Reloading /etc/samba/smb.conf: smbd only