nadsat/vintage_net_mobile

Mobile networking for VintageNet

VintageNetMobile

This library provides a VintageNet technology for using cellular modems. Currently, it supports the following modems:

• Quectel BG96 - VintageNetMobile.Modem.QuectelBG96
• Quectel EC25 - VintageNetMobile.Modem.QuectelEC25
• u-blox TOBY L2 - VintageNetMobile.Modem.UbloxTOBYL2
• Sierra Wireless HL8548 - VintageNetMobile.Modem.SierraHL8548

See the "Custom Modems" section for adding new modules.

To use this library, first add it to your project's dependency list:

def deps do
  [
    {:vintage_net_mobile, "~> 0.1.2"}
  ]
end

You will then need to configure VintageNet. All cellular modems currently show up on "ppp0", so configurations look like this:

VintageNet.configure("ppp0", %{
      type: VintageNetMobile,
      vintage_net_mobile: %{
        modem: your_modem,
        service_providers: your_service_providers
      }
    })

The :modem key should be set to your modem implementation. Cellular modems tend to be very similar. If vintage_net_mobile doesn't support your modem, see the customizing section. It may just be a copy/paste away.

The :service_providers key should be set to information provided by each of your service providers. It is common that this is a list of one item. Circumstances may require you to list more than one, though. Additionally, modem implementations may require more information. (It's also possible to hard-code the service provider in the modem implementation as a hack. In that case, this key isn't used and should be set to an empty list. This is useful when your cellular modem provides instructions that magically work and the AT commands that they give are confusing.)

Information for each service provider is a map with some or all of the following fields:

• :apn (required) - e.g., "access_point_name"
• :usage (optional) - :eps_bearer (LTE) or :pdp (UMTS/GPRS)

Your service provider should provide you with the information that you need to connect. Often it is just an APN. The Gnome project provides a database of service provider information that may also be useful.

Here's an example with a service provider list:

  %{
    type: VintageNetMobile,
    vintage_net_mobile: %{
      modem: your_modem,
      service_providers: [
        %{apn: "wireless.twilio.com"}
      ]
    }
  }

VintageNet Properties

In addition to the common vintage_net properties for all interface types, this technology reports one or more of the following:

Property	Values	Description
signal_asu	0-31,99	Reported Arbitrary Strength Unit (ASU)
signal_4bars	0-4	The signal level in "bars"
signal_dbm	-144 - -44	The signal level in dBm. Interpretation depends on the connection technology.
signal_rssi	0-31 or 99	An integer between 0-31 or 99
lac	0-65533	The Location Area Code (lac) for the current cell
cid	0-268435455	The Cell ID (cid) for the current cell
mcc	0-999	Mobile Country Code for the network
mnc	0-999	Mobile Network Code for the network
network	string	The network operator's name
access_technology	string	The technology currently in use to connect to the network
band	string	The frequency band in use
channel	integer	An integer that indicates the channel that's in use
iccid	string	The Integrated Circuit Card Identifier (ICCID)
imsi	string	The International Mobile Subscriber Identity (IMSI)

Please check your modem implementation for which properties it supports or run VintageNet.get_by_prefix(["interface", "ppp0"]) and see what happens.

Custom modems

VintageNetMobile allows you add custom modem implementations if the built-in ones don't work for you. See the VintageNetMobile.Modem behaviour.

In order to implement a modem, you will need:

1. Instructions for connecting to the modem via your Linux. Sometimes this involves usb_modeswitch or knowing which serial ports the modem exposes.
2. Example chat scripts. These are lists of AT commands and their expected responses for configuring the service provider and entering PPP mode.
3. (Optional) Instructions for checking the signal strength when connected.

One strategy is to see if there's an existing modem that looks similar to yours and modify it.

Serial AT command debugging

When porting vintage_net_mobile to a new cell modem, it can be useful to experiment with the modem directly. To do this, add a dependency to elixircom, rebuild, and then on the device, you can do things like this:

iex> Elixircom.run("/dev/ttyUSB2", speed: 115200)

Will allow you to run AT commands. To test everything is okay:

iex> Elixircom.run("/dev/ttyUSB2", speed: 115200)
# type at and press enter

OK

Your modem should supply a complete list of AT commands. The following may be useful:

Command	Description
at+csq	Signal Strength
at+csq=?	Query supported signal strength format
at+cfun?	Level of functionality
at+cfun=?	Query supported functionality levels
at+creg?	Check if the modem has registered to a provider.
at+cgreg?	Same as above for some modems
at+qccid	Query to obtain the Integrated Circuit Card Identifier
at+cimi	Query to obtain the International Mobile Subscriber Identity

System requirements

These requirements are believed to be the minimum needed to be added to the official Nerves systems.

Linux kernel

Enable PPP and drivers for your modem:

CONFIG_PPP=m
CONFIG_PPP_BSDCOMP=m
CONFIG_PPP_DEFLATE=m
CONFIG_PPP_FILTER=y
CONFIG_PPP_MPPE=m
CONFIG_PPP_MULTILINK=y
CONFIG_PPP_ASYNC=m
CONFIG_PPP_SYNC_TTY=m
CONFIG_USB_NET_CDC_NCM=m
CONFIG_USB_NET_HUAWEI_CDC_NCM=m
CONFIG_USB_NET_QMI_WWAN=m
CONFIG_USB_SERIAL_OPTION=m

Buildroot (nerves_defconfig)

Both pppd and usb_modeswitch are needed in the nerves_defconfig:

BR2_PACKAGE_USB_MODESWITCH=y
BR2_PACKAGE_PPPD=y
BR2_PACKAGE_PPPD_FILTER=y

Busybox

Add the following to your nerves_defconfig:

BR2_PACKAGE_BUSYBOX_CONFIG_FRAGMENT_FILES="${NERVES_DEFCONFIG_DIR}/busybox.fragment"

and then create busybox.fragment with the following:

CONFIG_MKNOD=y
CONFIG_WC=y