Just about every modem that can do actual real 4G cell phone connectivity is built around a SoC that blows the socks off your usual microcontroller.
The cheapest noname 4G USB stick you can buy now probably has a Qualcomm MSM8916 in it, and runs, I shit you not, Android.
As you can imagine, development with this kind of thing can be rather involved. No open development kits are available. There are no reference designs that don't require you to sign off on an NDA to access it, and Qualcomm wouldn't even want to talk to you unless you are at least "MOQ 100000+" tall.
The best you can do is get an existing modem module that hopefully doesn't bury too many of the interfaces you want, try to run your firmware on it, and then design your own board around that.
Which would probably yield a device that's inferior to most cheap smartphones or even feature phones.
The cheapest noname 4G USB stick you can buy now probably has a Qualcomm MSM8916 in it, and runs, I shit you not, Android.
You're not wrong, see also [1].
> and Qualcomm wouldn't even want to talk to you unless you are at least "MOQ 100000+"
These[2,3,4] definitely aren't MoQ "100000+" (I know this market), and yet they have gotten their hands on Android chipsets somehow, [2] even includes a cellular modem. Not cheap devices by any means though.
[1] https://nickvsnetworking.com/adventures-with-a-10-lte-mifi-d... [2] https://www.blindshell.com/eshop/blindshell-classic-3-eu [3] https://www.himsintl.com/en/blindness/view.php?idx=8 [4] https://www.humanware.com/microsite/bntouch/index.php?srslti...
Those products are almost always sourced from Chinese ODMs. They're the adults in the projects to the eyes of chip vendors, and the ODMs handle the quadrillion MOQ situation between them and vendors. Also products in [3] and [4] don't seem to support cellular? [3] smells AllWinner or MediaTek, [4] specifies TI OMAP in specifications page. Those are less NDA/bajilion MOQ bound.
Those specialized devices are usually made in partnership with some third party ODM that's big enough to get Qualcomm's attention. Same for things like warehouse barcode scanners that run Android.
Even if you could get attention of one, and get it to design and make a custom device that wouldn't break the bank? You are still likely to end up with that OEM owning the design and/or binding you with a small pile of NDAs.
Another option would be to find a supplier that can get you some "fell off the back of a truck" smartphone chipsets, and either design your own PCB and roll your own software, or use a "fell off the back of a truck" reference design, SDK and tooling too. You'd need to be a real hardcore motherfucker to do that though.
Reminds me of people using esp8266/esp32 chips just for wifi/bluetooth when paired with an AVR chip on an arduino.
I'm consistently puzzled why 5G versions of these SoC don't seem to exist for hardware hackers yet. I plain can't find any kind of 5G modem that isn't just a whole phone unless I pay like $1,000.
There are some available. For example: https://www.quectel.com/product/5g-redcap-rg255c-gl-m2/ - it costs around $120 per module. They have others: https://www.quectel.com/5g-iot-modules/
Which is pretty much what it costs for phone manufacturers right now.
I guess the real reason is that 4G is more than sufficient for pretty much anything, and it's going to be supported for the foreseeable future?
Where I live we are already talking about abandoning 2g, and 4g. (3g died a while back and 2g was kept as legacy network).
Really? Even satellites for off-grid messaging abandoned _5G_ and instead went with the good old LTE.
There was a DYI mobile phone project (real mobile phone, with GSM/3G calling and SMS). Abandoned now.
https://github.com/CircuitMess/CircuitMess-Ringo