Modular, wireless, open-source motion capture for everybody

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Back in 2016 I started looking for an open source motion capture suit but not finding anything I resolved to do myself. Fast forward two years, the situation hasn't improved much. There are now more suit options, but still not open source, and the only open suit I managed to find hadn't released the sources.

To contribute to solving this problem I'm evolving the first "hobby" suit into a cleaner, more robust one. This new version will be completely wireless, being composed of individual modules, which simplifies suiting up and prevents cable entanglement when in storage.

Finally, since each module is self-contained they can be used as individual inertial controllers for simple guidance or set in configurations different to that of a person, for example to provide feedback on mechanisms or animals.

Each module contains an nRF51822 microcontroller that reads orientation data from a BNO055 IMU and transmits it over BLE. 

In addition, an optional low-profile joystick can be mounted to add extra degrees of freedom to the system or to use for precision movements. 

The whole is powered by a 1400mAh Li-Ion battery and includes a USB integrated charger and a State-Of-Charge chip to keep track of the remaining percentage.

Modules can be put to work together in a mesh, or be used individually as a remote control with two smooth movement interfaces and jerk recognition to execute specifc actions.

  • 1 × BNO055 9DOF IMU
  • 1 × NRF51822 M0 microcontroller with BLE connectivity
  • 1 × MCP73831 Power Management ICs / Power Supply Support1
  • 1 × AP2112K Power Management ICs / Linear Voltage Regulators and LDOs
  • 1 × STC3117 State Of Charge IC

  • Estimated battery life

    Alvaro Ferrán Cifuentes04/16/2018 at 16:46 0 comments

    Since I'm still working on the PCB I can't measure the actual current being drawn by the system, so in order to get an estimate I turned to the datasheets of the various components I'm using.

    The largest consumers are the IMU, which in its highest consumption mode (9DOF @ 100Hz) draws about 13mA, and the controller. This one is divided into the CPU, asking about 5mA, and the BLE radio, which goes up to 30mA. The rest of the chips need very little current in comparison and can be neglected.

    The battery having a capacity of 1400mAh, a rough calculation puts the battery life at a over 28 hours of non stop data transmission per charge!

  • Basic schematics

    Alvaro Ferrán Cifuentes04/16/2018 at 16:39 0 comments

    The module's schematics are pretty simple:

    As we can see, the microcontroller will read over i2c both data from the IMU and the battery's State-Of-Charge (remaining percentage) as well as the joystick's position if it's present.

    All of this data will then be sent over Bluetooth 4.2 for the client to process.

    The battery is charged directly onboard, so plugging a microUSB cable is all that's needed.

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Tom Fleet wrote 10/25/2018 at 15:42 point

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