Rotary Cellphone (Original Project Post)

UPDATE, JANUARY 2021:

Quick history: This project went viral in early 2020. Concurrently, I was in the process of starting an open source tech company (Sky's Edge) for robotics, but everyone was asking me to sell the rotary cell phone. I reluctantly released a kit-version of the project described on this page, which I maintain for posterity, of which just over a hundred were sold. Having resigned myself to making un-smartphones a significant part of Sky's Edge, I concluded early on that there should be a much more refined, well-thought out version of the phone that would be easier to build, made from injection molded parts, operate on the 4G network, and possibly even be something that I could produce as a ready-made phone. I'm now accepting pre-orders for this new version (in kit-form), which I intend to start shipping before summer of 2021. HERE'S THE LINK. Note that these pre-orders are financing the production of the phone (like Kickstarter, but without actually using Kickstarter). Naturally, it's all still open source... I'll publicize the design data as soon as it's ready to ship.

Originally Posted February 10th, 2020:

Why a rotary cellphone? Because in a finicky, annoying, touchscreen world of hyperconnected people using phones they have no control over or understanding of, I wanted something that would be entirely mine, personal, and absolutely tactile, while also giving me an excuse for not texting. 

The point isn't to be anachronistic. It's to show that it's possible to have a perfectly usable phone that goes as far from having a touchscreen as I can imagine, and which in some ways may actually be more functional. More functional how? 

• Real, removable antenna with an SMA connector. Receptions is excellent, and if I really want to I could always attach a directional antenna.
• When I want a phone I don't have to navigate through menus to get to the phone "application". That's bullshit.
• If I want to call my husband, I can do so by pressing a single dedicated physical key which is dedicated to him. No menus. The point isn't to use the rotary dial every single time I want to make a call, which would get tiresome for daily use. The people I call most often are stored, and if I have to dial a new number or do something like set the volume, then I can use the fun and satisfying-to-use rotary dial.
• Nearly instantaneous, high resolution display of signal strength and battery level. No signal metering lag, and my LED bargraph gives 10 increments of resolution instead of just 4.
• The ePaper display is bistatic, meaning it doesn't take any energy to display a fixed message.
• When I want to change something about the phone's behavior, I just do it.
• The power switch is an actual slide switch. No holding down a stupid button to make it turn off and not being sure it really is turning off or what.

So it's not just a show-and-tell piece... My intent is to use it as my primary phone. It fits in a pocket; It's reasonably compact; calling the people I most often call is faster than with my old phone, and the battery lasts almost 24 hours.

Open Source Design:

3/21/2020 UPDATE: The latest version of all this information will be kept here instead. The below links are left intact for posterity.

The build notes will be updated soon and can be found here

The build video is here

The firmware is on github here (please contribute)

The latest KiCad files (the complete electrical design) are here

The STL files for the 3D printed enclosure and buttons are on the Thingiverse here

Project History:

Originally I was intent on making this a quick and dirty project. I laid everything out flat to make a proof of principle phone and used an Arduino Micro as the controller:

Then I thought I'd just stuff it into a 3D printed enclosure. Let's call this v1:

But this proved hopelessly delicate. Couldn't open it to fix something without breaking something else. OK, I guess a board layout is warranted. Did that and came up with v2:

It worked but had all sorts of issues. Battery life less than 2 hours. Used the Adafruit FONA 2G, which was a big mistake because I didn't realize the 2G networks are shutting down. Tantalizingly close to having the phone I really wanted. 

New design again. This is the final/current version. Whereas v2 used the ATmega2560 microcontroller, v3 uses the ATmega2560V, which is the low-power version of the chip. It's programmed in the Arduino IDE as though it's an Arduino Mega2560.

Top level schematic:

USB bridge:

This doesn't work. The bastard:

The layout looks like this. All the real KiCad design files are available in the link above:

Debugging the serial connection to the FONA:

Note the Rigol MSO1104Z in the background. A WONDERFUL random present from my husband David one year:

Complete, top down:

Showing the ePaper display:

The curved ePaper  on tha back was a later development in the creative process but it's now my favorite part. I think of the screen as having two sections... the part that's facing toward the top of the phone, and the part that's wholly on the back. In this way I can have relevant messages display on the top part "pager style", like the most recent missed call:

And still have the back available for other messages, or for  contacts lists, etc:

Another view: