Google has released the official Project Ara Module Developers Kit (MDK). The kit is of course supposed to provide developers with guidelines necessary to do their magic, but it also gives us more insight into Project Ara's basic building blocks.
Project Ara is based on an endoskeleton and the “endo” will be available in three different sizes. The 2x5 and 3x6 form factors are coming first, but later they’ll be complemented by a phabletish 4x7 form factor. The bigger the endo, the more freedom developers and consumer have to play around with.
Project Ara endoskeleton layout
The Mini layout is reserved for compact entry-level devices, with three different screen sizes along with an optional numeric keypad, which is quite rare on Android phones. The Medium layout features four different screen sizes and an optional QWERTY keyboard. The Large form factor is coming later, but it will also feature four different screen sizes and an optional keyboard.
We are a bit worried by the decision to use so many different aspect ratios, but luckily Android developers already have to deal with 4:3 and 16:9 displays – and everything in-between, of course.
The MDK outlines 11 different screen sizes in a range of form factors and (presumably) a lot of different resolutions. It’s a bit much really, but keep in mind that we are not looking at an actual product. Developers and vendors may settle for fewer screen sizes to cut costs and boost compatibility, trading off modularity for a somewhat lower BOM.
A word on modules and module sizes
Project Ara is the first full modular mobile platform and all modules will be standardised. The same approach could in theory be used for something completely different, including tablets or even DIY projects. Why bother with proprietary gear if you can use a Moto approved camera or battery module in your DIY project?
The modules will come in a few standard sizes. From the looks of it there are three module sizes, 2x2, 2x1 and 1x1. Google already has an arrangement with 3D Systems to 3D print some modules. 3D Systems recently announced that the first modules may come sooner than expected. It appears that the company will print module housings, but it is also developing conductive filament that could be used to print some circuitry (namely to connect the module’s brains to the connectors, or to print the connector itself in one go).
Pricing remains a big concern. Motorola already said its basic “gray phone” should cost about $50. However, that price only includes the 2x5 endoskeleton and the cheapest components known to man. It is highly unlikely that the 3x6 form factor with a proper screen and processor will end up close to that, or indeed the Moto G, which is still the best bang for buck Android phone you can buy today.