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Hardware

The Hardware subdirectory contains the ECAD design files for the OpenAXES PCB and its fabrication outputs, and MCAD files for the housing and calibration fixture.

This documentation describes Open Hardware and is licensed under the CERN-OHL-S v2 or any later version. See License below for more information.

PCB

This directory comprises the Altium Designer and KiCad EDA files. Altium Designer is a globally renowned PCB and electronic design software. KiCad, on the other hand, is a free open source software suite for EDA. The use of these two platforms ensures our project is accessible to a broad range of users.

The OpenAXES hardware platform was originally developed using Altium Designer. To allow for the use of open source EDA software tools it has been ported to KiCad. Known differences in the design files are only found in the silkscreen layers, so that there are no restrictions on the underlying functionality of the PCB.

Getting Started

To work with the files contained in this directory, you will need to have the appropriate software installed on your local machine.

Once you have installed the appropriate software, clone the repository and navigate to the respective subdirectories to access the project files.

Fabrication outpus

Fabrication outputs are provided in the PCB/Altium/Project Outputs for OpenAXES subdirectory. Output files for both single PCB and a panel optimized for mass production are included.

Deprecated components

  • BMI160; pin-compatible replacement: BMI270

Housing

The housing for the OpenAXES IMU can be found in the hardware/case subdirectory. It was designed in FreeCAD 0.20 for 3D-printing with a 0.4 mm diameter FDM nozzle. If the 3D printer is tunes correctly, the two halves of the case will snap together and provide a tight fit for the PCB.

Photograph of the OpenAXES PCB and case

There are cutouts for the USB port, the power switch, the analog pads on the bottom of the PCB, and for the JTAG adapter. The two holes at the top can be plugged with short pieces of transparent 3D-printing filament (1.75 mm diameter). These will act as light guides for the top LEDs next to the battery.

Programming adapter

The programming adapter found in the hardware/programming-adapter directory comprises a 3D-printable fixture and a single-layer PCB with spring loaded pins. These work together with the case, holding the IMU in place and contacting the six pads on the underside of the IMU PCB, for JTAG programming or debugging.

3D model and photograph of the programming adapter

The adapter can be used with any JTAG adapter compatible with the CC2652 processor and the Code Composer Studio IDE. During development, we used the LAUNCHXL-CC26X2R1 evaluation board from TI as a JTAG programmer. All JTAG signals on that board are accessible on a pin header, which is normally populated with jumpers. By removing the jumpers, the JTAG interface on the evaluation board can be used for external boards:

3D model and photograph of the programming adapter

Calibration fixture

The calibration fixture found in hardware/calibrator is an icosahedron (20-sided polyhedron) with a recess that accepts the IMU case. This fixture can be used together the with scripts in the calibration directory to obtain the sensor calibration coefficients for each individual unit.

Photograph of the calibration fixture with an IMU

License

Copyright 2023 Nils Stanislawski and Fritz Webering

This documentation describes Open Hardware and is licensed under the CERN-OHL-S-v2 or any later version.

You may redistribute and modify this documentation under the terms of the CERN OHL-S-v2 (https://ohwr.org/cern_ohl_s_v2.txt) or any later version. This documentation is distributed WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE. Please see the CERN OHL v2-S for applicable conditions

Source Location: https://github.com/IMS-AS-LUH/OpenAXES

For detailed license information on individual files, please see the file LICENSE.txt in the root folder of this repository.