Created How to use the 4G extension (markdown)

How-to-use-the-4G-extension.md

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+4G extension in uConsole is power down by default
+
+## first We need to power on the 4G extension
+
+### cm4 
+
+run `enable_4g_cm4.sh` or `uconsole-4g-cm enable`, depends on the version of your os image, both can do the same job
+
+wait for couple seconds ,then use `mmcli -L` to see if there is a modem like
+```
+/org/freedesktop/ModemManager1/Modem/0 [QUALCOMM INCORPORATED] SIMCOM_SIM7600G-H
+```
+
+and if unpack your back shell , you will see a green LED light is flashing on 4G ext
+
+### A06 and D1
+
+run `enable_4g.sh` or `uconsole-4g enable` depends on the version of your os image, both can do the same job
+
+wait for couple seconds ,then use `mmcli -L` to see if there is a modem like
+```
+/org/freedesktop/ModemManager1/Modem/0 [QUALCOMM INCORPORATED] SIMCOM_SIM7600G-H
+```
+and if unpack your back shell , you will see a green LED light is flashing on 4G ext
+
+## Connect to 4G network
+
+for this purpose,we need `nmcli` to create a connection first
+
+### find out the primary port
+
+```
+mmcli -m any | grep "primary port"
+
+```
+you will get like `cdc-wdm0` or  `ttyUSB2` , if you got `cdc-wdm0` , we suggest blacklisting some kernel modules by
+
+```
+$ cat /etc/modprobe.d/blacklist-qmi.conf
+blacklist qmi_wwan
+blacklist cdc_wdm
+```
+
+`ttyUSB2` is what we want,but **cdc-wdm0** is still worth to try if you know it well 
+ 
+### Create 4g net connection and bring it up
+
+```
+sudo nmcli c add type gsm ifname ttyUSB2 con-name 4gnet apn [yourapn] gsm.username [gsmusername] gsm.password [gsmpassword]
+```
+
+```
+sudo nmcli c up 4gnet
+```
+
+then if everything goes right, you will see **ppp0** in `sudo ifconfig` , which means you got an PPPoE connection and have an IP address
+
+
+The connectivity of 4G may vary in different countries around the world, so please make appropriate adjustments based on the situation of your ISP operator, which may require some Linux-related skills.
+