Motion Sensing Done Right

Many of our clients face a common challenge when undertaking IoT projects. They are experts in their own fields, and most of of them have a great idea, a proof-of-concept (PoC), or a sophisticated algorithm that addresses some specific need. They have simulated their solution in Matlab or Python and are eager to build and test a minimum viable product (MVP).

Unfortunately, designing a physical IoT device – or even prototyping one – is no easy task. Our experience has demonstrated that designers have a genuine need for a common, extensible, user-friendly, open source IoT platform that facilitates seamless interaction between the physical and the digital. Which is where we come in.

Our primary focus is on products and projects that sample motion, sense the physical world, and transmit the resulting data over Bluetooth Low-Energy (BLE) to smart devices running Android, iOS, Windows, and Linux. We created Bluetera I by stitching together key functionality, including communication hardware and basic motion sensing algorithms, as a way to provide the missing IoT platform our clients needed.

Bluetera II is the full realization of this same objective. It is open hardware running open firmware that includes motion sensors, power management, communication, and user-facing software – all woven together into a robust infrastructure for rapid IoT prototyping.

Bluetera II Demos

The demos in the video above were created primarily using the Windows-WPF application shown below. (You can find source code for this and other demos in our GitHub repository.)

Features

• Hardware - A tiny (18 x 18 mm) device with 9-axis motion sensors, an ARM MCU with BLE, battery charging circuitry, and multi-purpose IOs for externals sensors and peripherals
• Firmware - Open source infrastructure with embedded command and control, motion algorithms with built-in data exchange and IMU control, a BLE stack with an additional Protobuf abstraction layer, power management, and battery monitoring
• Open Source - Everything, from hardware to firmware to the software running on your mobile device or PC is strictly open-source. No strings attached
• Motion - 9-axis motion fusion based on the Madgwick Algorithm, which produces rotation data (quaternions) from the 6-axis InvenSense IMU and STM compass. The result is a stable, 1 kHz stream of rotation measurements and raw data.
• Google Protobuf - A communication abstraction layer that provides a simple yet flexible serial pipe between the physical layer (e.g. sensors) and the digital layer (e.g. your mobile device). Protobuf makes adding new messages and functionality as easy as 1-2-3.
• Power - A JST socket, a Micro USB connector, battery charging circuitry, and power management firmware allow you to power the device with any small, external Lithium-Ion battery.
• Extensions - 20 I/Os to support digital and analog peripherals and sensors, I²C, SPI, UART, PWM, and more.
• USB Type 2 - A Micro USB connector and firmware support for the USB 2 protocol enable fast, wired communication with the host and allow Bluetera II to serve as a BLE dongle.
• Rapid Development - A breadboard connected to the tiny Bluetera II provides a standard development matrix and facilitates quick and easy prototyping and debugging with external sensors and peripherals.
• SDK - Simplifies software development, with support for multiple operating systems and platforms, includes APIs, algorithms, and demos. The Bluetera II SDK is compatible with Linux, Android, iOS, and Windows. It also includes a plugin for the Unity 3D development platform.

Everything You Need for Your IoT Design

The exact contents of your order will depend on the package you select when backing our campaign, but the Bluetera II Developer Edition includes the following:

• 1x Bluetera II module
• 1x Extension board
• 1x Battery cable with a male JST connector
• 2x Male headers for Bluetera II
• 2x Female headers for the extension board
• 2x Headers to connect the extension board to an extension matrix
• 1x CSR BLE dongle (not shown)

The Bluetera II board itself includes a female JST connector that accommodates an external Lithium-Ion battery. (When soldering the battery cable to the battery, please take care to connect the VCC and GND correctly.)

Balance Range & Size to Suit Your Application

Bluetera II’s range is greatly affected by your choice of BLE module, which also impacts the overall dimensions of the board. The BC840 includes a highly compact, short-range PCB antenna. The BC840M includes a longer-range antenna that is slightly larger (but still quite small). And, if you want a Bluetera II that is somehow not tiny, your best bet is to choose a BC840E and attach a giant external antenna.

For most use cases, we recommend the long-range printed antenna (BCM840M). You can find more information on the manufacturer’s website.

Technical Specifications

Pinout Diagram

Comparison Table

Support & Documentation

All of our technical documentation resides in our GitHub repository, which is divided into four main sections:

• Bluetera Platform - A top-down overview of the entire system

and an installation guide

• Bluetera Hardware - Module schematics
• Bluetera Firmware - Firmware source code, a project build guide, and

instructions on programming and debugging your Bluetera II

• Bluetera SDKs - Software source code (currently available for Windows and Android), a project build guide, and a few examples

Protobuf Documentation

Google’s Protocol Buffers (often shortened to Protobuf) is a language-neutral, platform-neutral, extensible mechanism for serializing structured data. For Bluetera II, we use Protobuf to quickly add both uplink and downlink messages, which allows developers to focus on business logic instead of boilerplate code. Adding new functionality is as easy as:

• Modifying the protocol schema file (bluetera.proto)
• Adding a handler, in firmware, to implement the business logic
• Adding a handler or controller in the desktop application

Motion Sensor Documentation

Bluetera’s firmware uses the Madgwick sensor fusion algorithm, which transforms acceleration, gyro, and magnetometer data into quaternion rotation measurements.

The Madgwick algorithm is not only accurate and resource-efficient, it is open source (unlike most vendors’ fusion libraries) and remarkably customizable. This gives you the freedom to tailor the algorithm’s parameters for your specific application. In one use case, for example, we needed a high (1 kHz) quaternion data rate, but we could afford some drift after a while. Satisfying this requirement would not have been possible with vendor code, but Madgwick made it easy.

Manufacturing Plan

Our current plan is to work with Atid-el, a local manufacturer, to assemble the entire kit. We have also looked into working with PCBWAY in China, as we have used their service in the past, both for Bluetera I and for Bluetera II prototypes.

The MCUs will arrive at the production facility pre-programed with our latest Firmware, which will include self-test capabilities. Following production but prior to shipment, each Bluetera II unit will be hooked to an external power source, via the USB adapter, and tested.

Fulfillment & Logistics

Once we have tested and verified all units, the entire batch will be sent to the US for distribution to backers via Crowd Supply’s fulfillment services.

Delivery within the US is included in the listed price, while delivery outside the US will incur the international surcharge specified for the relevant pledge level. Deliveries to EU countries, Switzerland, Australia, and Canada will have VAT and customs duties paid in advance, so backers in these countries will have no need to deal with Customs.

See Crowd Supply’s article on Ordering, Paying, Shipping: The Details for more information on delivery, VAT payments, etc.

Risks & Challenges

Designing, developing, building, and testing hardware is never easy. Bugs can always slip by, and they are not always easy to fix. Fortunately, we have extensive knowledge related to designing, developing, and testing IoT hardware. Bluetera II is our fourth IoT project, and our second product in the Bluetera series. Our experience with the first-generation Bluetera board, in particular, will reduce R&D risks substantially and help us deliver a high-quality, second-generation product.

Shipping logistics come with their own set of risks: component shortages, bad batches, and shipping delays, to name just a few. We are working with well-respected vendors and production facilities to avoid problems like these, and we have a Plan-B manufacturing alternative just in case.

Naturally, we will keep backers appraised through project updates should any setbacks occur during manufacturing or fulfillment.