Someone modded a Nokia 3210 to work with 4G!
He designed a replacement motherboard, and wrote his own firmware in C.
I think this is very cool, and can’t wait to see where it goes.
From the dev
Hi again!
A while ago I posted about building a replacement motherboard for the original 1999 Nokia 3210. Quite a few people asked for the source files, a working demonstration, and somewhere to follow the project. I finally have a proper update!
The project is now called Sisu, and I’ve published both the hardware design and firmware source.
The 3210 was my first phone. The goal is still to keep as much of that experience as possible: the original case, buttons, monochrome screen, familiar menus, sounds and games. LTE lets it keep making calls on networks where the original 2G hardware can no longer connect.
The prototype has made VoLTE calls and handled SMS(Tested in USA on AT&T network). The firmware is a new implementation written in C, recreating the old interface. And yes, Snake is there 
(and custom made Pac Man too!)
For anyone following the hardware, the current board uses an RP2354B and a Telit LE910C1-WWX modem. There have been a few board revisions since the first post, and I’m still working on antenna tuning and corrections for the next revision.
A few answers to questions from the earlier threads:
- Can you buy one? There are no boards or kits for sale yet. The files are available, but the current revision needs corrections described in the hardware errata.
- Do you need an original 3210? Yes. This replaces its motherboard and reuses the donor phone’s parts.
- Battery life? I’ve published the early measurements. They suggest almost 4 days in standby. The current prototype uses the original NiMH battery format; the lithium option discussed earlier isn’t supported in this version.
- WhatsApp and other extras? I considered some possibilities in the first thread, but have decided to keep Sisu focused on the original phone experience. No WhatsApp, Wi-Fi, Bluetooth or browser is planned. (Maybe Telegram as SMS dialog?.. idk, not too soon)
Everything now has a home:
Project website and progress
Hardware files · Firmware source
Discord
Thanks to everyone who kept checking in, offered help, or simply cheered the project on. Questions, contributions and other old-phone projects are very welcome!