轉自 http://blog.sina.com.cn/s/blog_7880d3350102wb92.html

在ARM平臺上實現4G模組的PPP撥號上網，參考網上的資料和自己的理解，從一無所知到開發完成花了一週多。最後看到ARM板ping通www.baidu.com時甚是高興，現將此過程整理如下。當然，除此之外要做的工作還有很多。

4G模組使用的SIMTECH 的SIM7100C，SIM7100C帶有UART和USB介面，在考慮速度上我們使用USB介面和ARM進行通訊。所以向linux核心新增3G模組的驅動(USB轉串列埠驅動)和PPP協議的支援，然後編譯核心並下載到開發板。

1. 編譯核心

◇ 大容量儲存驅動

> Device Drivers > USB support
make ARCH=arm menuconfig配置USB驅動：
<*>     USB Mass Storage support
[*]       USB Mass Storage verbose debug
<*>       Realtek Card Reader support
[*]         Realtek Card Reader autosuspend support
<*>       Datafab Compact Flash Reader support

◇ USB驅動

> Device Drivers > USB support
<*>   Inventra Highspeed Dual Role Controller (TI, ADI, ...)   
            MUSB Mode Selection (Dual Role mode)  --->             
    <*>     Platform Glue Layer (TI DSPS platforms)  --->           
        MUSB DMA mode (Disable DMA (always use PIO))  --->
<*>   USB Serial Converter support  --->
[*]      USBGeneric Serial Driver 
<*>     USBdriver for GSM and CDMA modems

◇ PPP驅動

> Device Drivers > 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      
<*>   SLIP (serial line) support      
[*]   CSLIP compressed headers
 

2. 交叉編譯libusb

下載usblib庫和libusb-compat

https://sourceforge.net/projects/libusb/files/

[email protected]:/opt/usb-tools/libusb-1.0.20# mkdir install
configure: error: "udev support requested but libudev not installed"(解決：新增--disable-udev)
[email protected]:/opt/usb-tools/libusb-1.0.20# ./configure --host=arm-none-linux-gnueabi --prefix=/opt/usb-tools/libusb-1.0.20/install --disable-udev
[email protected]:/opt/usb-tools/libusb-1.0.20# make
[email protected]:/opt/usb-tools/libusb-1.0.20# make install
 
新增環境變數 http://www.linuxidc.com/Linux/2011-03/33432.htm（PKG_CONFIG_PATH設定）

[email protected]:/opt/usb-tools/libusb-1.0.20# export PKG_CONFIG_PATH=/opt/usb-tools/libusb-1.0.20/install/lib/pkgconfig:$PKG_CONFIG_PATH
[email protected]:/opt/usb-tools/libusb-1.0.20# echo $PKG_CONFIG_PATH
 
編譯libusb-compat：

[email protected]:/opt/usb-tools/libusb-compat-0.1.5# ./configure --host=arm-none-linux-gnueabi --prefix=/opt/usb-tools/libusb-compat-0.1.5/install
[email protected]:/opt/usb-tools/libusb-compat-0.1.5# make
[email protected]:/opt/usb-tools/libusb-compat-0.1.5# make install
 
將生成的libusb-1.0.20和libusb-compat-0.1.5下的庫檔案複製到ARM板上的linux的/lib下面即可。
 
3. 交叉編譯4G模組驅動

交叉編譯GobiSerial.c(ARCH=arm CC=arm-none-linux-gnueabi-gcc)，得到GobiSerial.ko。複製到ARM板安裝驅動

#insmod GobiSerial.ko
 
4. 檢視驅動執行狀況

插上4G模組，虛擬出6個ttyUSB，它們分別是：

[email protected]:/# ls /dev/ttyUSB*
/dev/ttyUSB0  /dev/ttyUSB1  /dev/ttyUSB2  /dev/ttyUSB3  /dev/ttyUSB4  /dev/ttyUSB5
1) /dev/ttyUSB0-diag port for output developing messages
2) /dev/ttyUSB1- NMEA port for GPS NMEA data output
3) /dev/ttyUSB2-AT port for AT commands
4) /dev/ttyUSB3-Modem port for ppp-dial
5) /dev/ttyUSB4-audio port
6) /dev/ttyUSB5-Virtual Net card
 
插上U盤，提示裝置執行：

[75097.986054] usb 2-1: New USB device found, idVendor=058f, idProduct=6387
[75097.993167] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[75098.000689] usb 2-1: Product: Mass Storage
[75098.004995] usb 2-1: Manufacturer: Generic
[75098.009342] usb 2-1: SerialNumber: AC3DF2EE
[75098.024341] usb-storage 2-1:1.0: USB Mass Storage device detected
[75098.049922] scsi0 : usb-storage 2-1:1.0

lsusb命令檢視結果：

Bus 001 Device 002: ID 1e0e:9001
Bus 002 Device 002: ID 058f:6387
Bus 001 Device 001: ID 1d6b:0002
Bus 002 Device 001: ID 1d6b:0002

5. 交叉編譯PPP

參見：http://blog.sina.com.cn/s/blog_7880d3350102wb3e.html
 
6. 撥號指令碼設定

[email protected]:/etc/ppp# vi gprs-connect-chat
#Chat script for China Mobile, used SIMCOM sim4100 TD module.
TIMEOUT 15
ABORT "DELAYED"
ABORT "BUSY"
ABORT "ERROR"
ABORT "NO DIALTONE"
ABORT "NO CARRIER"
TIMEOUT 40
'' \rAT
OK ATS0=0
OK ATE0V1
OK AT+CGDCONT=1,"IP","CMNET"
OK AT+CGEQREQ=1,2,128,384,,,0,,,,,,
OK ATDT*99*1#
CONNECT
[email protected]:/etc/ppp/peers# vi gprsdial
#/etc/ppp/peers/gprsdial
# This is pppd script for China Mobile, used SIMCOM SIM7100 Module
# Usage: root>pppd call gprs
#Interface should be used is the interface which connects physics interface of S
/dev/ttyUSB3
115200
crtscts
modem
#noauth
debug
nodetach
#hide-password
usepeerdns
noipdefault
defaultroute
user "cmnet"
0.0.0.0:0.0.0.0
#ipcp-accept-local
#ipcp-accept-remote
#lcp-echo-failure 12
#lcp-echo-interval 3
#noccp
#novj
#novjccomp
#persist
connect '/usr/sbin/chat -s -v -f /etc/ppp/gprs-connect-chat'
#disconnect '/bin/chat -v -f /etc/ppp/gprs-disconnect-chat'
 
6. 撥號

[email protected]: pppd call gprsdial
 
6. 測試

撥號之後進行測試，發現可以ping通ip但是無法ping通域名。這需要設定/etc/resolv.conf來新增DNS解析伺服器的地址

檔案/etc/resolv.conf配置DNS客戶，它包含了主機的域名搜尋順序和DNS伺服器的地址，每一行應包含一個關鍵字和一個或多個的由空格隔開的引數。下面是一個例子檔案： 
domain test.com
search www.test.com test.com
nameserver 202.96.128.86
nameserver 202.96.128.166
nameserver   #定義DNS伺服器的IP地址
domain       #定義本地域名
search       #定義域名的搜尋列表
sortlist     #對返回的域名進行排序
主要是nameserver關鍵字，如果沒指定nameserver就找不到DNS伺服器，其它關鍵字是可選的。
    我這裡只設置了兩個DNS，如下：
ameserver 114.114.114.114
nameserver 8.8.8.8
 
參考文件：
How to use the SIM7100 module in Linux.pdf
http://blog.csdn.net/hanmengaidudu/article/details/17099737
http://www.linuxidc.com/Linux/2011-03/33430p2.htm
http://www.linuxidc.com/Linux/2011-03/33430.htm