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Is it possible that there are no verified 4G USB dongles for RPI, or the following link is out of date?

If so, why is it? If not, where are they listed?

Yigal
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2 Answers2

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The elinux pages are sometimes out-of-date, but it is also worth noting that those lists are not exhauastive by nature, hopefully that does not require further explanation.

Whether a device will work is largely dependent on whether a driver for it exists, which is dependent on the operating system. Elinux is obviously linux-centric and I'll presume you're using some form of such too, e.g., Raspbian, although what's really of concern here is the kernel ("Linux" proper actually only refers to the kernel) since that's what controls hardware and where drivers are implemented, and there is really only one series of the kernel version in use on the pi regardless of distro.

There are various 4G USB modem drivers referenced by USB ID in the kernel source. The hard part, without actually having the dongle, is getting the USB ID appropriate to the chipset it uses. Sometimes you can find them online. USB IDs are in the form xxxx:xxxx, where the x's are hexadecimal digits. For example, searching "Airtel MF825A USB id" yields various hits including this one, from which it is pretty easy to garner the USB ID is 19d2:1408.

Now for the even more tedious part, checking the kernel source to see if there's a driver that references this. Despite the awkwardness, this is a pretty reliable technique because it is those numbers that USB devices report when they are plugged in, and then the kernel uses them to locate a driver.

All the USB networking driver sources are in the drivers/net/usb directory, which for the pi kernel in particular you can browse here although it is unlikely to be any different than the vanilla version in this context. Anyway, grep 19d2 * in that directory does turn up a list of things from the qmi_wwan driver, but it doesn't include 1408 -- however, there is a list of other models identified in comments there. If we have one of those, the question then is whether that driver was included in the pre-built pi kernel; you can browser the modules in your own /lib/modules/xxx (for xxx, check uname -r) or in the firmware repo in the Foundation's github. It's the kernel/drivers/net/usb directory we want to look in.1

And low and behold, qmi_wwan.ko is there, so things such as the "ZTE MF683", mentioned at line 718 of that source, should work.

That's an idealized version of a procedure. Basically, if you have something in mind start by searching online for "linux Acme XY700" and go from there. Don't include "raspberry pi" in the search or the results will be much more limited, but once you believe that the device does have a linux driver, you probably do want to make sure it is included in the pi kernel (e.g., by asking here directly).

1. Beware the difference between the kernel/drivers/net/... directory and kernel/net/... directory with this stuff.

goldilocks
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Here is also a 4G dongle verified in the miscellaneous section from Microsoft - that is if you are on Windows 10 IoT Core.

Jnr
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