简介 随着工业发展，嵌入式设备接入网络的需求日益增多，在没有有线或者无线以太网的环境下，直接通过3G/4G Modem连接运营商网络来接入互联网不失为一个好方法，本文就着重介绍基于ARM平台的嵌入式设备在Embedded Linux下使用3G/4G Modem的方法。 目前市面上的3G/4G modem和主机的连接方式主要有串口、USB和mini-PCIE，串口模块比较传统且使用比较简单，而mini-PCIE在工业设备中目前应用还不广泛，因此本文使用USB 3G/4G modem来进行演示。 硬件准备 嵌入式平台基于Toradex Colibri i.MX6工业产品级ARM核心板搭配Colibri开发载板，Embedded Linux采用Toradex官方发布兼容Yocto Project 的Linux V2.5版本。 3G Modem使用华为 E303s WCDMA Modem，支持中国联通的3G网络 Linux Kernel准备 关于Linux kernel源代码下载及基本编译更新操作请参考这里，本文不再赘述，只简单列出操作如下： a). 下载Linux kernel源代码 b). 下载安装Toolchain，并link到 “ ~/gcc-linaro “ 目录 $ wget http://releases.linaro.org/14.11/components/toolchain/binaries/arm-linux-gnueabihf/gcc-linaro-4.9-2014.11-x86_64_arm-linux-gnueabihf.tar.xz $ tar xvf gcc-linaro-4.9-2014.11-x86_64_arm-linux-gnueabihf.tar.xz $ ln -s gcc-linaro-4.9-2014.11-x86_64_arm-linux-gnueabihf gcc-linaro   c). 设置环境变量 $ export ARCH=arm $ export PATH=~/gcc-linaro/bin/:$PATH $ export CROSS_COMPILE=arm-linux-gnueabihf-   d). 配置 $ make colibri_imx6_defconfig $ make menuconfig      //添加下面列出功能 -------------------- [*] Network device support  --->        <*>   PPP (point-to-point protocol) support        <*>     PPP BSD-Compress compression         <*>     PPP Deflate compression        [*]     PPP filtering        <*>     PPP MPPE compression (encryption)        [*]     PPP multilink support        <*>     PPP over Ethernet        <*>     PPP support for async serial ports        <*>     PPP support for sync tty ports   [*] USB support  --->        <*>     USB Modem (CDC ACM) support   [*] USB support  --->     <*>   USB Serial Converter support  --->               <*>   USB driver for GSM and CDMA modems --------------------   e). 重新编译kernel image $ make -j3 uImage LOADADDR=10008000 2>&1 | tee build.log   f). 升级目标板 根据本章节开始提供的参考升级目标板到新的kernel image 相关软件准备 1). PPP Toradex image默认已经安装，如果其他ARM平台image也是基于Yocto/OpenEmbedded环境编译，可以在local.conf文件中添加如下选项后编译 ----------------- IMAGE_INSTALL_append = " ppp" ----------------- 2). usb-modesiwtch-2.3.0 a). 需要libusb-1.0.x，先从这里下载源文件并解压 b). 使用上一章节配置的ToolChain如下设置交叉编译libusb $ sudo CC="/home/xxx/gcc-linaro/bin/arm-linux-gnueabihf-gcc" CXX="/home/xxx/gcc-linaro/bin/arm-linux-gnueabihf-g++" ./configure --host=arm-linux-gnueabihf --prefix=/home/xxx/gcc-linaro --disable-udev $ make $ make install c). 从这里下载usb-modesiwtch并解压 d). 如下修改usb-modesiwtch 目录下Makefile ---------------- CC          = ~/gcc-linaro/bin/arm-linux-gnueabihf-gcc CFLAGS      += -Wall -I/home/xxx/gcc-linaro/include -L/home/xxx/gcc-linaro/lib ---------------- e).交叉编译usb-modesiwtch $ make f). 从这里下载usb-modeswitch-data，和上面步骤编译出的usb-modesiwtch可执行文件一起上传到目标板 配置Modem连接网络 目前比较新的3G/4G都支持Ethernet模式和Fallback模式，而老一些的模块只支持Fallback模式，请根据所需模块情况自行参考下面操作。 1). Ethernet模式 a). 将E303s 3G Modem连接目标板，由于Modem上包含为了给Windows系统提供驱动而部署的存储分区，Linux默认将设备识别成USB Mass Storage设备 root@colibri-imx6:/home# lsusb Bus 001 Device 004: ID 12d1:1f01 Huawei Technologies Co., Ltd. E353/E3131 (Mass storage mode) …… b). 如下修改usb-modeswitch-data-20160112/usb_modeswitch.d目录下的12d1:1f01文件 ----------------------- # Huawei E303s Ethernet Mode DefaultVendor=0x12d1 DefaultProduct=0x1f01 TargetVendor=0x12d1 TargetProduct=0x14db MessageEndPoint = "0x01" MessageContent="55534243123456780000000000000a11062000000000000100000000000000" ------------------------ c). 使用usb-modeswitch工具将modem设置为Ethernet mode root@colibri-imx6:/home# ./usb_modeswitch -c 12d1:1f01 …… root@colibri-imx6:/home# [  840.027676] usb 1-1.1: USB disconnect, device number 4 [  840.284299] usb 1-1.1: new high-speed USB device number 6 using ci_hdrc [  840.427810] cdc_ether 1-1.1:1.0 eth1: register 'cdc_ether' at usb-ci_hdrc.0-1.1, CDC Ethernet Device, 58:2c:80:13:92:63   lsusb查看 root@colibri-imx6:/home# lsusb Bus 001 Device 005: ID 12d1:14db Huawei Technologies Co., Ltd. E353/E3131 …… d). 查看网络，出现eth1，正确获取ip并连接到网络，下面就可以用使用以太网同样方法使用网络了 root@colibri-imx6:/home# ifconfig …… eth1      Link encap:Ethernet  HWaddr 58:2C:80:13:92:63            inet addr:192.168.1.100  Bcast:192.168.1.255  Mask:255.255.255.0           inet6 addr: fe80::5a2c:80ff:fe13:9263/64 Scope:Link           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1           RX packets:37 errors:0 dropped:0 overruns:0 frame:0           TX packets:69 errors:0 dropped:0 overruns:0 carrier:0           collisions:0 txqueuelen:1000           RX bytes:6899 (6.7 KiB)  TX bytes:10381 (10.1 KiB) …… e). 验证网络连接 root@colibri-imx6:/home# ping www.baidu.com PING www.baidu.com (61.135.169.121): 56 data bytes 64 bytes from 61.135.169.121: seq=0 ttl=51 time=88.261 ms 64 bytes from 61.135.169.121: seq=1 ttl=51 time=77.998 ms 64 bytes from 61.135.169.121: seq=2 ttl=51 time=68.410 ms 64 bytes from 61.135.169.121: seq=3 ttl=51 time=68.242 ms 64 bytes from 61.135.169.121: seq=4 ttl=51 time=68.166 ms 2). Fallback模式 有一些较老型号的2G/3G Modem只支持这个模式，无需再用usb-modeswitch转换，可以直接参考下面转换后的操作部分。 a). 如下修改usb-modeswitch-data-20160112/usb_modeswitch.d目录下的12d1:1f01文件 ----------------------- # Huawei E303s Fallback Mode DefaultVendor=0x12d1 DefaultProduct=0x1f01 TargetVendor=0x12d1 TargetProduct=0x1001 MessageEndPoint = "0x01" MessageContent="55534243123456780000000000000011063000000100010000000000000000" NoDriverLoading=0 ------------------------ b). 使用usb-modeswitch工具将modem设置为Fallback mode root@colibri-imx6:/home# ./usb_modeswitch -c 12d1:1f01 …… root@colibri-imx6:/home# [ 2090.566190] usb 1-1.1: new high-speed USB device number 8 using ci_hdrc [ 2090.701092] option 1-1.1:1.0: GSM modem (1-port) converter detected [ 2090.713488] usb 1-1.1: GSM modem (1-port) converter now attached to ttyUSB0 [ 2090.723517] option 1-1.1:1.1: GSM modem (1-port) converter detected [ 2090.731817] usb 1-1.1: GSM modem (1-port) converter now attached to ttyUSB1 [ 2090.740318] option 1-1.1:1.2: GSM modem (1-port) converter detected [ 2090.748184] usb 1-1.1: GSM modem (1-port) converter now attached to ttyUSB   lsusb 查看 root@colibri-imx6:/home# lsusb Bus 001 Device 008: ID 12d1:1001 Huawei Technologies Co., Ltd. E169/E620/E800 HSDPA Modem …… c). 测试连接 root@colibri-imx6:/home# ls -l /dev/ttyUSB* crw-rw----    1 root     dialout   188,   0 Apr 11 09:49 /dev/ttyUSB0 crw-rw----    1 root     dialout   188,   1 Apr 11 09:49 /dev/ttyUSB1 crw-rw----    1 root     dialout   188,   2 Apr 11 09:49 /dev/ttyUSB2   root@colibri-imx6:/home# minicom -D /dev/ttyUSB0 ------------------ Welcome to minicom 2.7 OPTIONS: I18n Compiled on Nov  3 2015, 04:06:26. Port /dev/ttyUSB0, 09:53:44 Press CTRL-A Z for help on special keys   AT OK -------------------- d). 编写ppp连接配置文件wcdma, wcdma-chat-connect和wcdma-chat-disconnect root@colibri-imx6:/etc/ppp/peers# vi wcdma ----------------- nodetach lock /dev/ttyUSB0 115200 user "card" password "card" crtscts #hide-password show-password usepeerdns noauth noipdefault novj novjccomp noccp defaultroute ipcp-accept-local ipcp-accept-remote connect '/usr/sbin/chat -s -v -f /etc/ppp/peers/wcdma-chat-connect' disconnect '/usr/sbin/chat -s -v -f /etc/ppp/peers/wcdma-chat-disconnect' ----------------------   root@colibri-imx6:/etc/ppp/peers# vi wcdma-chat-connect -------------------- ABORT "BUSY" ABORT "NO CARRIER" ABORT "NO DIALTONE" ABORT "ERROR" ABORT "NO ANSWER" TIMEOUT 120 "" AT OK ATZ OK AT+CGDCONT=1,"IP","3gnet",,0,0 OK-AT-OK ATDT*99# CONNECT dc --------------------------   root@colibri-imx6:/etc/ppp/peers# vi wcdma-chat-disconnect ----------------------- ABORT "ERROR" ABORT "NO DIALTONE" SAY "NSending break to the modem " ""k" ""+++ATH" SAY " Good bay " --------------------------- e). 连接网络 root@colibri-imx6:/etc/ppp/peers# pppd call wcdma …… ATDT*99#^M^M CONNECT  -- got it   send (d) Serial connection established. Using interface ppp0 Connect: ppp0 <--> /dev/ttyUSB0 CHAP authentication succeeded: Welcome!! CHAP authentication succeeded Could not determine remote IP address: defaulting to 10.64.64.64 local  IP address 10.91.228.253 remote IP address 10.64.64.64 primary   DNS address 221.12.1.227 secondary DNS address 221.12.33.227   查看网络状态 root@colibri-imx6:/etc/ppp/peers# ifconfig …… ppp0      Link encap:Point-to-Point Protocol            inet addr:10.23.107.61  P-t-P:10.64.64.64  Mask:255.255.255.255           UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1           RX packets:6 errors:0 dropped:0 overruns:0 frame:0           TX packets:6 errors:0 dropped:0 overruns:0 carrier:0           collisions:0 txqueuelen:3           RX bytes:84 (84.0 B)  TX bytes:102 (102.0 B) f). 测试网络 root@colibri-imx6:/etc/ppp/peers# echo nameserver 221.12.1.227 > /etc/resolv.conf                 //设置DNS服务器 root@colibri-imx6:/etc/ppp/peers# ping www.baidu.com PING www.baidu.com (61.135.169.121): 56 data bytes 64 bytes from 61.135.169.121: seq=0 ttl=52 time=218.477 ms 64 bytes from 61.135.169.121: seq=1 ttl=52 time=68.066 ms 64 bytes from 61.135.169.121: seq=2 ttl=52 time=107.773 ms 64 bytes from 61.135.169.121: seq=3 ttl=52 time=77.604 ms 64 bytes from 61.135.169.121: seq=4 ttl=52 time=77.339 ms   总结 根据上述两种模式的测试结果，第一种Ethernet mode相对速度要更稳定一些，因此对于支持两种模式的modem更建议采用Ethernet mode；另外串口modem使用配置也可以参考Fallback mode。本文虽以E303s为例，但其他3G/4G Modem的配置也是类似，只是需要确定对应模式的Vendor ID，Product ID和Message。 参考文档 https://www.toradex.cn/zh_cn/computer-on-modules/colibri-arm-family/nxp-freescale-imx6 https://www.toradex.cn/zh_cn/products/carrier-board/colibri-evaluation-carrier-board http://developer.toradex.com/software/linux/linux-software http://www.draisberghof.de/usb_modeswitch/ http://www.cnblogs.com/ziqiuqiandao/archive/2013/06/06/3120972.html