硬件描述：EC20模块封装成标准的PCIe接口，和系统之家通讯主要通过usb通讯。

系统描述：此处使用的是Linux 3.0.1。

一、驱动支持

首先需要对Linux内核驱动做一定的修改，使操作系统能够支持EC20。

1. Add VID add PID

File: [KERNEL]/drivers/usb/serial/option.c

#if 1 //Added by Quectel
    { USB_DEVICE(0x05C6, 0x9090) }, /* Quectel UC15 */
    { USB_DEVICE(0x05C6, 0x9003) }, /* Quectel UC20 */
    { USB_DEVICE(0x05C6, 0x9215) }, /* Quectel EC20 */
    { USB_DEVICE(0x2C7C, 0x0125) }, /* Quectel EC25/EC20 R2.0 */
    { USB_DEVICE(0x2C7C, 0x0121) }, /* Quectel EC21 */
 #endif

2. Add the Zero Packet Mechanism

As required by the USB protocol, you need to add the mechanism for processing zero packets during bulkout transmission.

File: [KERNEL]/drivers/usb/serial/usb_wwan.c

static struct urb *usb_wwan_setup_urb(struct usb_serial *serial, int endpoint,
                      int dir, void *ctx, char *buf, int len,
                      void (*callback) (struct urb *))
{
    struct urb *urb;

    if (endpoint == -1)
        return NULL;    /* endpoint not needed */

    urb = usb_alloc_urb(0, GFP_KERNEL); /* No ISO */
    if (urb == NULL) {
        dbg("%s: alloc for endpoint %d failed.", __func__, endpoint);
        return NULL;
    }

    /* Fill URB using supplied data. */
    usb_fill_bulk_urb(urb, serial->dev,
              usb_sndbulkpipe(serial->dev, endpoint) | dir,
              buf, len, callback, ctx);

 #if 1      // 2017.3.7 add by zhaoxiaodong
    if (dir == USB_DIR_OUT) {
        struct usb_device_descriptor *desc = &serial->dev->descriptor;
        if (desc->idVendor == cpu_to_le16(0x05C6) && desc->idProduct == cpu_to_le16(0x9090))
            urb->transfer_flags |= URB_ZERO_PACKET;
        if (desc->idVendor == cpu_to_le16(0x05C6) && desc->idProduct == cpu_to_le16(0x9003))
            urb->transfer_flags |= URB_ZERO_PACKET;
        if (desc->idVendor == cpu_to_le16(0x05C6) && desc->idProduct == cpu_to_le16(0x9215))
            urb->transfer_flags |= URB_ZERO_PACKET;
        if (desc->idVendor == cpu_to_le16(0x2C7C))
            urb->transfer_flags |= URB_ZERO_PACKET;
    }
 #endif 

    return urb;
}

3. Add Reset Resume

Some USB host controllers/USB hubs will lost power or be reset when MCU entering into suspend/sleep

mode, and they cannot resume USB devices when MCU exiting from suspend/sleep mode; instead, they

will operate reset-resume. You should add the following statements.

For Linux Kernel Version newer than 3.4:

File: [KERNEL]/drivers/usb/serial/option.c

static struct usb_serial_driver option_1port_device = {
……
#ifdef CONFIG_PM
    .suspend = usb_wwan_suspend,
    .resume = usb_wwan_resume,
#if 1 //Added by Quectel
    .reset_resume = usb_wwan_resume,
#endif
#endif
};

For Linux Kernel Version older than 3.5:

File: [KERNEL]/drivers/usb/serial/ usb-serial.c

static struct usb_driver usb_serial_driver = {
    .name =     "usbserial",
    .probe =    usb_serial_probe,
    .disconnect =   usb_serial_disconnect,
    .suspend =  usb_serial_suspend,
    .resume =   usb_serial_resume,
 #if 1      // 2017.3.7 add by zhaoxiaodong
    .reset_resume = usb_serial_resume,
 #endif 

    .no_dynamic_id =    1,
    .supports_autosuspend = 1,
};

4. Modify Kernel Configuration

Step 1:

cd <your kernel directory>

Step 2:Set your environment variables, and import your board’s defconfig. The following is an example

for Raspeberrypi board

export ARCH=arm
export CROSS_COMPILE=arm-none-linux-gnueabimake bcmrpi_defconfig

Step 3:

make menuconfig

Step 4:Enable CONFIG_USB_SERIAL_OPTION

[*] Device Drivers →
　　[*] USB Support →
　　　　[*] USB Serial Converter support →
　　　　　　[*] USB driver for GSM and CDMA modems

Step 5:Configure Kernel to Support PPP

[*] Device Drivers →
　　[*] Network device support →
　　　　[*] PPP (point-to-point protocol) support

5. 编译内核

make

将编译好的内核下载到开发板。

二、模块测试

将重新编译好的内核下载到开发板之后，待系统重新启动，肉驱动添加正确，在/dev/目录下会出现如下设备节点：

/dev/ttyUSB0  /dev/ttyUSB1  /dev/ttyUSB2  /dev/ttyUSB3

EC20的AT端口是/dev/ttyUSB2，现在你可以使用UART端口工具如“minicom”或“busybox microcom”测试AT功能，结果如下：

#busybox microcom /dev/ttyUSB2
ati;+csub
Quectel
EC20F
Revision: EC20CEFDR02A09M4G

SubEdition: V04

OK

三、拨号

方案一

通过几个不同的配置文件，在拨号的时候选择相应的配置文件，现将配置文件列举如下：

/etc/ppp/peers/quectel-ppp

# /etc/ppp/peers/quectel-pppd
# Usage:root>pppd call quectel-pppd
#Modem path, like /dev/ttyUSB3,/dev/ttyACM0, depend on your module, default path is /dev/ttyUSB3
/dev/ttyUSB3 115200
#Insert the username and password for authentication, default user and password are test
user "test" password "test"
# The chat script, customize your APN in this file
connect 'chat -s -v -f /etc/ppp/peers/quectel-chat-connect'
# The close script
disconnect 'chat -s -v -f /etc/ppp/peers/quectel-chat-disconnect'
# Hide password in debug messages
hide-password
# The phone is not required to authenticate
noauth
# Debug info from pppd
debug
# If you want to use the HSDPA link as your gateway
defaultroute
# pppd must not propose any IP address to the peer
noipdefault
# No ppp compression
novj
novjccomp
noccp
ipcp-accept-local
ipcp-accept-remote
local
# For sanity, keep a lock on the serial line
lock
modem
dump
nodetach
# Hardware flow control
nocrtscts
remotename 3gppp
ipparam 3gppp
ipcp-max-failure 30
# Ask the peer for up to 2 DNS server addresses
usepeerdns

/etc/ppp/peers/quectel-chat-connect

# /etc/ppp/peers/quectel-chat-connect
ABORT "BUSY"
ABORT "NO CARRIER"
ABORT "NO DIALTONE"
ABORT "ERROR"
ABORT "NO ANSWER"
TIMEOUT 30
"" AT
OK ATE0
OK ATI;+CSUB;+CSQ;+CPIN?;+COPS?;+CGREG?;&D2
# Insert the APN provided by your network operator, default apn is 3gnet
OK AT+CGDCONT=1,"IP","3gnet",,0,0
OK ATD*99#
CONNECT

/etc/ppp/peers/quectel-chat-disconnect

# /etc/ppp/peers/quectel-chat-disconnect
ABORT "ERROR"
ABORT "NO DIALTONE"
SAY "\nSending break to the modem\n"
""  +++
""  +++
""  +++
SAY "\nGoodbay\n"

编辑好这几个文件之后，便可以通过pppd进行拨号：

# pppd call quectel-ppp &

如果拨号成功会有以下信息打印出来：

[root@zx64352 peers]# pppd call quectel-ppp
pppd options in effect:
debug           # (from /etc/ppp/peers/quectel-ppp)
nodetach                # (from /etc/ppp/peers/quectel-ppp)
dump            # (from /etc/ppp/peers/quectel-ppp)
noauth          # (from /etc/ppp/peers/quectel-ppp)
user test               # (from /etc/ppp/peers/quectel-ppp)
password ??????         # (from /etc/ppp/peers/quectel-ppp)
remotename 3gppp                # (from /etc/ppp/peers/quectel-ppp)
/dev/ttyUSB3            # (from /etc/ppp/peers/quectel-ppp)
115200          # (from /etc/ppp/peers/quectel-ppp)
lock            # (from /etc/ppp/peers/quectel-ppp)
connect chat -s -v -f /etc/ppp/peers/quectel-chat-connect               # (from /etc/ppp/peers/quectel-ppp)
disconnect chat -s -v -f /etc/ppp/peers/quectel-chat-disconnect         # (from /etc/ppp/peers/quectel-ppp)
nocrtscts               # (from /etc/ppp/peers/quectel-ppp)
modem           # (from /etc/ppp/peers/quectel-ppp)
hide-password           # (from /etc/ppp/peers/quectel-ppp)
novj            # (from /etc/ppp/peers/quectel-ppp)
novjccomp               # (from /etc/ppp/peers/quectel-ppp)
ipcp-accept-local               # (from /etc/ppp/peers/quectel-ppp)
ipcp-accept-remote              # (from /etc/ppp/peers/quectel-ppp)
ipparam 3gppp           # (from /etc/ppp/peers/quectel-ppp)
noipdefault             # (from /etc/ppp/peers/quectel-ppp)
ipcp-max-failure 30             # (from /etc/ppp/peers/quectel-ppp)
defaultroute            # (from /etc/ppp/peers/quectel-ppp)
usepeerdns              # (from /etc/ppp/peers/quectel-ppp)
noccp           # (from /etc/ppp/peers/quectel-ppp)
abort on (BUSY)
abort on (NO CARRIER)
abort on (NO DIALTONE)
abort on (ERROR)
abort on (NO ANSWER)
timeout set to 30 seconds
send (AT^M)
expect (OK)
AT^M^M
OK
 -- got it

send (ATE0^M)
expect (OK)
^M
ATE0^M^M
OK
 -- got it

send (ATI;+CSUB;+CSQ;+CPIN?;+COPS?;+CGREG?;&D2^M)
expect (OK)
^M
^M
Quectel^M
EC20F^M
Revision: EC20CEFDR02A09M4G^M
^M
SubEdition: V04^M
^M
+CSQ: 14,99^M
^M
+CPIN: READY^M
^M
+COPS: 0^M
^M
+CGREG: 0,0^M
^M
OK
 -- got it

send (AT+CGDCONT=1,"IP","3gnet",,0,0^M)
expect (OK)
^M
^M
OK
 -- got it

send (ATD*99#^M)
expect (CONNECT)
^M
^M
CONNECT
 -- got it

Script chat -s -v -f /etc/ppp/peers/quectel-chat-connect finished (pid 785), status = 0x0
Serial connection established.
using channel 1
Using interface ppp0
Connect: ppp0 <--> /dev/ttyUSB3
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x1f2b413> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x0 <asyncmap 0x0> <auth chap MD5> <magic 0xd11eadc2> <pcomp> <accomp>]
sent [LCP ConfAck id=0x0 <asyncmap 0x0> <auth chap MD5> <magic 0xd11eadc2> <pcomp> <accomp>]
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0x1f2b413> <pcomp> <accomp>]
rcvd [LCP DiscReq id=0x1 magic=0xd11eadc2]
rcvd [CHAP Challenge id=0x1 <40aedf97298706e7675d614c0cea9175>, name = "UMTS_CHAP_SRVR"]
sent [CHAP Response id=0x1 <1bf312e7aa43615e474c49c28fbbaca5>, name = "test"]
rcvd [CHAP Success id=0x1 ""]
CHAP authentication succeeded
CHAP authentication succeeded
sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <ms-dns1 0.0.0.0> <ms-dns2 0.0.0.0>]
rcvd [IPCP ConfReq id=0x0]
sent [IPCP ConfNak id=0x0 <addr 0.0.0.0>]
rcvd [IPCP ConfNak id=0x1 <addr 10.35.149.45> <ms-dns1 218.4.4.4> <ms-dns2 218.2.2.2>]
sent [IPCP ConfReq id=0x2 <addr 10.35.149.45> <ms-dns1 218.4.4.4> <ms-dns2 218.2.2.2>]
rcvd [IPCP ConfReq id=0x1]
sent [IPCP ConfAck id=0x1]
rcvd [IPCP ConfAck id=0x2 <addr 10.35.149.45> <ms-dns1 218.4.4.4> <ms-dns2 218.2.2.2>]
Could not determine remote IP address: defaulting to 10.64.64.64
local  IP address 10.35.149.45
remote IP address 10.64.64.64
primary   DNS address 218.4.4.4
secondary DNS address 218.2.2.2

此时也会在/etc/ppp/目录下生成resolv.conf文件，存放pppd拨号获取到的DNS，可以将改文件拷贝到/etc/目录下，这样便可以进行DNS解析了，至此开发板也可以通过EC20模块连接到互联网了。

方案二

方案一中的端口号、APN、用户名、密码等都是直接写在配置文件中，这样如果要更换这些内容的话要频繁修改配置文件，既消耗时间，又不太方便。所以便将几个配置文件融合到一个脚本中，并且可以通过传递参数那样修改需要修改的内容，脚本内容如下：

/etc/ppp/peers/quectel-pppd.sh

#!/bin/sh

#quectel-pppd devname apn user password
echo "quectel-pppd options in effect:"
QL_DEVNAME=/dev/ttyUSB3
QL_APN=3gnet
QL_USER=user
QL_PASSWORD=passwd
if [ $# -ge 1 ]; then
    QL_DEVNAME=$1  
    echo "devname   $QL_DEVNAME    # (from command line)"
else
    echo "devname   $QL_DEVNAME    # (default)"
fi
if [ $# -ge 2 ]; then
    QL_APN=$2  
    echo "apn       $QL_APN    # (from command line)"
else
    echo "apn       $QL_APN    # (default)"
fi
if [ $# -ge 3 ]; then
    QL_USER=$3 
    echo "user      $QL_USER   # (from command line)"
else
    echo "user      $QL_USER   # (default)"
fi
if [ $# -ge 4 ]; then
    QL_PASSWORD=$4 
    echo "password  $QL_PASSWORD   # (from command line)"
else
    echo "password  $QL_PASSWORD   # (default)"
fi

CONNECT="'chat -s -v ABORT BUSY ABORT \"NO CARRIER\" ABORT \"NO DIALTONE\" ABORT ERROR ABORT \"NO ANSWER\" TIMEOUT 30 \
\"\" AT OK ATE0 OK ATI\;+CSUB\;+CSQ\;+CPIN?\;+COPS?\;+CGREG?\;\&D2 \
OK AT+CGDCONT=1,\\\"IP\\\",\\\"$QL_APN\\\",,0,0 OK ATD*99# CONNECT'"

pppd $QL_DEVNAME 115200 user "$QL_USER" password "$QL_PASSWORD" \
connect "'$CONNECT'" \
disconnect 'chat -s -v ABORT ERROR ABORT "NO DIALTONE" SAY "\nSending break to the modem\n" "" +++ "" +++ "" +++ SAY "\nGood bay\n"' \
noauth debug defaultroute noipdefault novj novjccomp noccp ipcp-accept-local ipcp-accept-remote ipcp-max-configure 30 local lock modem dump nodetach nocrtscts usepeerdns 

拨号

/etc/ppp/peers/quectel-pppd.sh &

输出信息跟方案一输出一样，同样会生成/etc/ppp/resolv.conf文件。

注：在进行拨号之前一定要确保没有默认网关，如果已经设置了其他网卡的默认网关了，则4G模块没法正常上网，需要删除原来的默认网关，现以网卡eth0为例：

route del default
route del -host 255.255.255.255 dev eth0