簡介

隨著工業發展，嵌入式裝置接入網路的需求日益增多，在沒有有線或者無線乙太網的環境下，直接通過3G/4G Modem連線運營商網路來接入網際網路不失為一個好方法，本文就著重介紹基於ARM平臺的嵌入式裝置在Embedded Linux下使用3G/4G Modem的方法。

目前市面上的3G/4G modem和主機的連線方式主要有串列埠、USB和mini-PCIE，串列埠模組比較傳統且使用比較簡單，而mini-PCIE在工業裝置中目前應用還不廣泛，因此本文使用USB 3G/4G modem來進行演示。

硬體準備

嵌入式平臺基於Toradex Colibri i.MX6工業產品級ARM核心板搭配Colibri開發載板，Embedded Linux採用Toradex官方釋出相容Yocto Project 的

3G Modem使用華為 E303s WCDMA Modem，支援中國聯通的3G網路

Linux Kernel準備

關於Linux kernel原始碼下載及基本編譯更新操作請參考這裡，本文不再贅述，只簡單列出操作如下：

a). 下載Linux kernel原始碼

b). 下載安裝Toolchain，並link到 “ ~/gcc-linaro “ 目錄

$ 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). 設定環境變數

$ export ARCH=arm

$ export PATH=~/gcc-linaro/bin/:$PATH

$ export CROSS_COMPILE=arm-linux-gnueabihf-

d). 配置

$ make colibri_imx6_defconfig

$ make menuconfig      //新增下面列出功能

--------------------

[*] 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). 重新編譯kernel image

$ make -j3 uImage LOADADDR=10008000 2>&1 | tee build.log

f). 升級目標板

根據本章節開始提供的參考升級目標板到新的kernel image

相關軟體準備

1). PPP

Toradex image預設已經安裝，如果其他ARM平臺image也是基於Yocto/OpenEmbedded環境編譯，可以在local.conf檔案中新增如下選項後編譯

-----------------

IMAGE_INSTALL_append = " ppp"

-----------------

2). usb-modesiwtch-2.3.0

a). 需要libusb-1.0.x，先從這裡下載原始檔並解壓

b). 使用上一章節配置的ToolChain如下設定交叉編譯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). 從這裡下載usb-modesiwtch並解壓

d). 如下修改usb-modesiwtch 目錄下Makefile

----------------

CC          = ~/gcc-linaro/bin/arm-linux-gnueabihf-gcc

CFLAGS      += -Wall -I/home/xxx/gcc-linaro/include -L/home/xxx/gcc-linaro/lib

----------------

e).交叉編譯usb-modesiwtch

$ make

f). 從這裡下載usb-modeswitch-data，和上面步驟編譯出的usb-modesiwtch可執行檔案一起上傳到目標板

配置Modem連線網路

目前比較新的3G/4G都支援Ethernet模式和Fallback模式，而老一些的模組只支援Fallback模式，請根據所需模組情況自行參考下面操作。

1). Ethernet模式

a). 將E303s 3G Modem連線目標板，由於Modem上包含為了給Windows系統提供驅動而部署的儲存分割槽，Linux預設將裝置識別成USB Mass Storage裝置

[email protected]:/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目錄下的12d1:1f01檔案

-----------------------

# Huawei E303s Ethernet Mode

DefaultVendor=0x12d1

DefaultProduct=0x1f01

TargetVendor=0x12d1

TargetProduct=0x14db

MessageEndPoint = "0x01"

MessageContent="55534243123456780000000000000a11062000000000000100000000000000"

------------------------

c). 使用usb-modeswitch工具將modem設定為Ethernet mode

[email protected]:/home# ./usb_modeswitch -c 12d1:1f01

……

[email protected]:/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檢視

[email protected]:/home# lsusb

Bus 001 Device 005: ID 12d1:14db Huawei Technologies Co., Ltd. E353/E3131

……

d). 檢視網路，出現eth1，正確獲取ip並連線到網路，下面就可以用使用乙太網同樣方法使用網路了

[email protected]:/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). 驗證網路連線

[email protected]:/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

有一些較老型號的2G/3G Modem只支援這個模式，無需再用usb-modeswitch轉換，可以直接參考下面轉換後的操作部分。

a). 如下修改usb-modeswitch-data-20160112/usb_modeswitch.d目錄下的12d1:1f01檔案

-----------------------

# Huawei E303s Fallback Mode

DefaultVendor=0x12d1

DefaultProduct=0x1f01

TargetVendor=0x12d1

TargetProduct=0x1001

MessageEndPoint = "0x01"

MessageContent="55534243123456780000000000000011063000000100010000000000000000"

NoDriverLoading=0

------------------------

b). 使用usb-modeswitch工具將modem設定為Fallback mode

[email protected]:/home# ./usb_modeswitch -c 12d1\:1f01

……

[email protected]:/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 檢視

[email protected]:/home# lsusb

Bus 001 Device 008: ID 12d1:1001 Huawei Technologies Co., Ltd. E169/E620/E800 HSDPA Modem

……

c). 測試連線

[email protected]:/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

[email protected]:/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). 編寫ppp連線配置檔案wcdma, wcdma-chat-connect和wcdma-chat-disconnect

[email protected]:/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'

----------------------

[email protected]:/etc/ppp/peers# vi wcdma-chat-connect

--------------------

ABORT "BUSY"

ABORT "NO CARRIER"

ABORT "NO DIALTONE"

ABORT "ERROR"

ABORT "NO ANSWER"

TIMEOUT 120

"" AT

OK \rATZ

OK \rAT+CGDCONT=1,"IP","3gnet",,0,0

OK-AT-OK ATDT*99#

CONNECT \d\c

--------------------------

[email protected]:/etc/ppp/peers# vi wcdma-chat-disconnect

-----------------------

ABORT "ERROR"

ABORT "NO DIALTONE"

SAY "\NSending break to the modem\n"

""\k"

""+++ATH"

SAY "\nGood bay\n"

---------------------------

e). 連線網路

[email protected]:/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

檢視網路狀態

[email protected]:/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). 測試網路

[email protected]:/etc/ppp/peers# echo nameserver 221.12.1.227 > /etc/resolv.conf                 //設定DNS伺服器

[email protected]:/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

總結

根據上述兩種模式的測試結果，第一種Ethernet mode相對速度要更穩定一些，因此對於支援兩種模式的modem更建議採用Ethernet mode；另外串列埠modem使用配置也可以參考Fallback mode。本文雖以E303s為例，但其他3G/4G Modem的配置也是類似，只是需要確定對應模式的Vendor ID，Product ID和Message。

參考文件