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Modular Smartphone System

Olav Næss, April 2021

The modern smartphone is a quite complex system, containing various sensors and other useful components. But its reconfigurability - the potentials for configuring and expanding the hardware for various purposes and preferences - is bad.

Google made a half-hearted attempt at making a reconfigurable smartphone system. It was called the Ara system, and it was cancelled as it turned out that it was difficult to change modules in a few seconds.

This reconfiguration speed requirement was unwise. We who want this flexibility would certainly accept sitting at a table a few minutes, working with a screwdriver. It would be like changing plug-in cards in a non-portable computer.

It was also unwise to replace the smartphone with a module collection, as this would be much more expensive and unreliable. A modern computer has a fully functional motherboard, and the plug-in cards are merely supplemental.

In the same manner, a modular smartphone system should use a conventional smartphone as the core and main module.

The whole system (depicted below) fits within a seemingly ordinary phone case, of the type which can be opened and closed like a book. These are normally shaped and produced for specific phone models, as they need holes for differen back camera configurations. And the phone is generally pushed into a tightly fitting edge frame having holes in certain places.

A more sensible point of departure would be the generalized model for all smartphones having approximately the same size. This case grips the phone from the sides, between two spring-loaded clamps. The clamps and the phone can slide up and down so that the back cameras can look over the top of the (hole-less) back-plate of the case. Such a case can be made in a few sizes like S/M/L/XL, and perhaps a few tablet sizes.

The configuration

The system illustration below shows a typical configuration. At the bottom end of the phone is a USB hub with a micro USB or a USB-C contact. A movable or exchangeable contact system may accomodate both. A small hub version may extend to only one side so that a 3.5mm audio connection isn't blocked.

The hub has two USB cables going out to:

On the other end and the lower side it has various USB ports.

External cameras

The main camera will be a 15-20mm thick cylindrical (super)zoom camera. The lens front is angled (with an internal mirror) like it was in the thin (20mm thick) Minolta cameras.

Also the top end of the left page is reserved for the cameras. Both areas are Velcro-covered, and the camera has Velcro on its outer (plane) side, so the camera can be placed to the left or right.

It should be possible to rotate the cylindrical camera at least 180° within the outer casing, so that the zoom lens can see forwards and backwards. In intermediate angles, the phone can be placed on e.g. a table for shooting/filming steadily forwards. Being able to zoom in on one's own face, is much better than looking in a mirror.

It should be possible to mount another mini camera on the end of the zoom camera. This could be a strong wide angle camera. If the front of the cameras had rails for filter holders, a filter or macro lens could slide out of the way or over to the other camera. (Cameras tend to have macro capabilities only when zoomed to Wide - a bad alternative.)

The phone, as well as the components below and above, could be mounted on a metal plate covering the whole page. It should then be possible to slide the plate upwards until the camera to be used get an unobstructed view above the upper edge of the case - in the same manner as is done with a traditional universal case. The plate should have a window as indicated by the dotted rectangle in the illustration. This should be large enough to give all back cameras an unobstructed view.

Alternatively, the phone, hub and cameras could be fixed to the case, and this case could have such a window. There should then be plastic/metal plates available for closing the window. These could have holes exactly in front of the cameras, and this little plate would be the only system part to be adapted to the specific phone model. If the plate is of metal, it could have threads for screwing in accessory lenses.

A mirror-less zoom camera

A mirror-less lens - looking along its cylinder axis - could be used on the left page. The case will then be opened 90° for self-portraits and 270° for normal shooting. (And 180° for sneaky shooting.)

Camera rotation will now be used for changing between portrait and landscape mode.

It will, however, not be easy to accomodate a second cylindrical camera with this configuration.

The phone system case can stand up as a tripod when opened 60-300°, but only the mirrored camera will then have a vertical adjustment capability.

The other page

The page facing the phone should be covered with Velcro, and the modules for this system should have matching Velcro backs. The whole page could be covered by one large battery, or have an assortement as shown in the illustration: one half-size battery + a secondary hub with USB-attached modules. These could be for

Alternative hubs in this position could also interface to I2C, SPI and/or UART.

A module at the case edge could be a heat imaging camera. (A conventional heat camera like Flir could be placed on the end of a hub.)

The thickness of the modules could be 6 or 8mm. If the thin modules are used, a thin e-paper display could cover this page (exept the camera space). It could be 2mm thick, except for the electronics part which is plugged into the two upper module connectors. It should download a book from the phone, and could then be used for reading while the phone is turned off.

It should be possible to have a thin middle page between the two main pages. This would normally be for a screen protector covering the left side modules. And/or a display could be there.

The phone may be used only as a computer, or may be replaced by a computer. It may then not be important to fold the system for pocketability, so it can be mounted - opened or closed - on the back of a large display.


An optional keyboard could be mounted as a page at the left side. When attached, the display is used in landscape mode. If the keyboard can be used detached, it can be used lying flat on a table, while the system stands like a (90-270° opened) book, thus permitting the display to be used in portrait mode.