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Modular Moto Z Android phone supports DIY and RPi HAT add-ons

Jul 29, 2016 — by Eric Brown — 7,048 views

Motorola and Element14 have launched a development kit for creating add-on modules for the new modular Moto Z smartphone, including an adapter for RPi HATs.

We don’t usually cover smartphones here at HackerBoards because most don’t offer much opportunity for hardware hacking. Yet, Lenovo’s Motorola Mobility subsidiary has spiced up the smartphone space this week by announcing a modular, hackable “Moto Mods” backplate expansion system for its new Android-based Moto Z smartphones.

Moto Z phone and backplate (left) and combined with a Moto Mods Projector
(click images to enlarge)

In addition, Motorola has teamed up with Element14 to offer a $125, hardware-based Moto Mods Development Kit for building custom Moto Mods. Using this, developers can build their own Moto Mods add-ons for applications such as infrared cameras, e-ink displays, game controllers and printers to metal detectors, inventory tag readers, blood pressure monitors, and air pollution sensors, says Element14.

Moto Z modularity
(click images to enlarge)

The company is also providing MDK developers with four optional Personality Cards, that act as reference designs for functions to be included within custom, application-specific Moto Mods. These currently include $40 Audio, $40 Battery, $50 Display, and $40 Temperature Sensor cards. The cards integrate end-to-end examples with open-sourced, Nuttx RTOS-based Moto Mods firmware and an Android app.

Moto Mods Development Kit exploded view
(click image to enlarge)

Element14 also shipped a $40 Moto Mods HAT Adapter Board that lets you add commercially available Raspberry Pi HAT add-ons to the phone. The adapter lets you attach most commercial Raspberry Pi HATs and control them from the Moto Z phone, as if it were a Raspberry Pi (see farther below).

The Moto Z Droid and Moto Z Force Droid phones run Android 6.0 on a Qualcomm Snapdragon 820 SoC (see farther below for details.) The phones are currently available to consumers with three Moto Mods options: a $60 Incipio offGRID Power Pack, an $80 JBL SoundBoost Speaker, and a $300 Moto Insta-Share Projector.

The Moto Z Droid (see farther below) is only 5.19mm thick without a Moto Mods backplate. According to this AnandTech review, the Power Pack option adds 6.2mm, for a total of less than 11.4mm. The 6.9mm thick Force model, however, ends up at 13.2mm and 242 grams. This is only slightly thinner than the original, 13.7mm thick Motorola Droid slider phone from 2009, one of the first Android phones to seriously compete with the iPhone. The AnandTech review praised the overall concept and the Moto Mods magnetic attachment technology, but had a problem with the weight of the systems and the draw on battery.

Motorola, which started building Linux-based mobile phones in the early years of the millennium, such as the circa-2004 A780, has long been pushing modular technology. Like earlier Moto branded Android phones, the Moto Z offers the usual wide array of cosmetic options, which you can mix and match using its “build yours” shopping pages.

The backplate technology appears to have been inspired by the modular backplate modules of the Project Ara concept phone developed at Motorola’s Advanced Research and Projects (ATAP) R&D group when Google owned Motorola. Project Ara, which is now owned by Google along with ATAP, was itself based on the similar, and related, Phonebloks project.

Conceptually, Moto Mods are more similar to the The Other Half backplates envisioned for the original Jolla phone in that only one module can be used at a time. Other modular phones include the Fairphone 2, which lets you add internal snap-in modules for mainboard, display, mic, cameras, and battery. A similar internal approach to modularity is being attempted by the open source, Linux-based Neo900 phone project, which recently resumed buying components after some PayPal troubles.

Inside the Moto Mods Development Kit

The Moto Mods Development Kit has the same basic architecture and form-factor as the commercial Moto Mods options. The MDK connects to the back of the Moto Z (or Z Force) with a snap-on magnetic attachment system called Smart Surface that enables hot swapping of Moto Mods. All communication and power travels over a system of pins made from 23K gold with a hydrophobic nano coating, says Element14. A hole is cut out for the rear camera, and the phone’s wireless, audio, and imaging performance are unaffected, says the company.

Architecture overviews of the Moto Mods (left) and Moto Mods Development Kit
(click images to enlarge)

The MDK comprises a Reference Moto Mod, a Perforated Card that acts as a breadboard, and an example cover. The Reference Moto Mod provides the core interfaces to the Moto Z platform, as well as a “Moto Mod Micro Controller,” generally referred to as the “MuC,” which runs the open source NuttX RTOS. (NuttX is still the most widely used OS for APM/ArduPilot and PX4 drones, although Linux is coming on fast thanks to the Linux Foundation’s Dronecode project.) The Reference Moto Mod also features GPIO, standard peripheral interfaces, and power and charging control.

Reference Moto Mod and Personality Card details
(click images to enlarge)

The MuC is a Cortex-M4 based STML476, which according to the ST product page runs at up to 80MHz with up to 128KB of SRAM and up to 1MB flash. The MuC runs custom firmware, and communicates both with peripherals and the Moto Z, with which it shares a “Greybus” abstraction layer. It also includes a MuC bootloader that uses Trusted Firmware Transfer Format (TFTF) for firmware updates.

Reference Moto Mod block diagram
(click image to enlarge)

The Reference Moto Mod is equipped with a Moto High Speed Bridge (Moto Bridge) IPC for high-speed interfaces including CSI (camera), DSI (display), and I2S (audio). The power and charging block provides regulated and unregulated power control, battery selection, and charging paths.

Moto Mods MuC (left) and Bridge architecture diagrams
(click images to enlarge)

Three USB ports are available. There’s a USB Type-C for USB 3.1 OTG and USB 2.0 host signals, and a USB Type-C for debug. In addition, there’s a micro-USB B connector for USB 2.0 host and MyDP (Mobility DisplayPort, or SlimPort), which enables DP signals over USB.

The MDK ships with a Perforated Board that acts as a breadboard for experimentation. It includes 26 rows of solder points at 2.54mm pitch and power bus pins on each side.

Moto Mods HAT Perforated Board
(click image to enlarge)

The Perforated Board, as well as optional Personality Boards and custom Moto Mods created using the MDK, attach to the Reference Moto Mod via an 80-pin connector. Each Personality Card includes an onboard EEPROM queried by the MuC bootloader when it’s attached. If needed, the MuC bootloader will request the Moto Z to download and install the latest firmware needed for the card.

The open source NuttX-based Moto Mod Firmware is used to control internal Moto Mod functions. NuttX is configured at compile time using the same configuration tool as the Linux Kernel. Beyond this, firmware development mostly involves updating the hardware Manifest with specific configurations and writing device protocol drivers, says Motorola.

Moto Mod Android SDK

The final piece is the Moto Mod Android SDK, which lets Android apps discover, communicate and interact with Moto Mods. Motorola has integrated support for many Moto Mod protocols directly into Android. In addition, new APIs enable developers to build their own applications and communicate with a custom-designed Moto Mod. Developers can host their Android apps in the Google Play store, and the apps are automatically downloaded and installed when the associated Moto Mod is attached for first time.

Moto Mods Android software architecture
(click image to enlarge)

Exclusive rights to selling the Moto Mods Development Kit (MDK) are owned by Element14, the North American division of UK-based Raspberry Pi manufacturer Premier Farnell. The latter is being acquired by Avnet in a £691 million ($907 million) deal.

As part of the Moto Mods Developer Program, Lenovo Capital will be applying $1 million to bring the best Moto Mods ideas to market. Developers can build their prototypes using the MDK, and then submit them to Motorola for review. The best ideas will be pitched for potential funding at Lenovo Capital.

Moto Mods HAT Adapter Board

Element14’s HAT Adapter Board provides an interesting and immediate differentiator for the Moto Z: the ability to run most Raspberry Pi HAT (Hardware Attached on Top) add-ons, and access them from Android apps. This HAT Adapter plugs into the MDK’s 80-pin connector like other Personality Cards, and provides RPi compatible 40-pin expansion header, 15-pin camera, and 15-pin display connectors exactly where HAT cards expect to find them.

Moto Mods HAT Adapter Board
(click image to enlarge)

The catch is that existing Raspbian based firmware and drivers must be ported to the MuC’s NuttX stack. Certain tasks and queues may require redesign. You also need to create an Android app to access the HAT’s functions.

Moto Z Phones

The Moto Z phones are now available from multiple sources, including Verizon Wireless, with off-contract prices starting at $624 and $720 (Force) with 32GB storage. The phones run Android 6.0.1 “Marshmallow” on a Qualcomm Snapdragon 820 with four Cortex-A72-like cores and an Adreno 530 GPU. The phones ship with 4GB of LPDDR4, and you can boost onboard UFS storage to 64GB or further expand via microSD.

Moto Z
(click image to enlarge)

The Moto Z phones feature 5.5-inch, 2560 x 1440 AMOLED touchscreens, 5-megapixel front-facing cameras, and 13- or 21-megapixel (Force) rear-facing cameras. They are further equipped with WiFi-AC, Bluetooth 4.1 LE, LTE, GPS, NFC, speakers, and a wide range of sensors, not to mention whatever you might want to add with a custom Moto Mod. Battery life is 30 or 40 hours, depending on the model.

Moto Mods video overview

Further information

The $125 Moto Mods Development Kit, $40 to $50 Personality Cards, and $40 Moto Mods HAT Adapter Board are now available for sale at Element14, although the HAT adapter is listed as out of stock. The Moto Z Droid and Moto Z Droid Force are available for $624 and $720, respectively, off contract with 32GB storage.

More information may be found at the Element14 Moto Mods MDK product page, which offers links to buying pages. More on the Moto Z may be found in the Motorola Moto Z announcement and Moto Z and Moto Mods product page.

More technical information on Moto Mods and the MDK may be found at the Moto Mods Developer site.

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