Position sensor

Introduction

This Android application uses the built-in accelerometer and gyroscope to implement an Inertial Navigation Unit (INU) and trace the path the user has taken so far.

Certain INU parameters are configurable via adb shell and a TCP socket connection. Instructions below.

Pre-requisites

Compile

• Android SDK 27
• Android Build Tools v27.0.2
• Android Support Repository

Run

• Minimun SDK version 21
• adb shell

Getting Started

To interface with the application via the command line connect the phone to the computer via USB and then run the following from the command line to:

adb forward tcp:6100 tcp:6666

The above command forwards the computer (host) port 6100 to the app's port 6666 change the first parameter to whatever you need, leave the second parameter intact.

Once setup the forwarding rule, open up any TCP socket application and connect to the specified host port (port 6100 in the above example)

Once connected, send the following string to start listening to position updates:

start [-p polling rate] [-e event detection threshold] [-xt movement detection threshold (x-axis)] [-yt movement detection threshold (y-axis)]

For example, running

start -p 500 -e 0.2 -xt 1.5 -yt 1.0

Will start the position updates with an log rate of 500ms, set the event detection threshold to 0.2 and movement detection threshold to 1.5 for the x-axis and 1.0 for the y-axis

The default values are -p 100ms, -e 0.3, -xt 1.0 and -yt 1.0, if not specified.

The app output format is as follows:

[xraw:val, yraw:val, xsqr:val, ysqr:val, compass:val, pitch:val]

xraw and yraw are the acceleromenter's raw output value.

xsqr and ysqr are the squarewave output value, let it be 1, -1 or 0

compass is the degree with respect to earth's geomagnetic north

pitch is the smartphone's 'lean' value in degrees.

Workflow

Included is a basic TCP socket script called client.py and the apk called Application-debug.apk

Usual workflow would go as follows:

1. Execute adb forward tcp:6666 tcp:6666
2. Start the application, stay at 'camera' mode
3. Execute client.py script and type start with your desired parameters (start alone works fine with default parameters)
4. Check client.py stdout for sensor log output

Demo

The number in the middle of the camera view represents the movement orientation with respect to the magnetic north.

The view below is where the user's trajectory path is drawn in real time. The backgroud 'map' view is static and only serves as a placeholder.

SideNotes

You have to be in the 'camera' mode for the TCP command to work, don't send the command when in 'chart' mode. Fix is on the way

Whenever running a new configuration, kill and restart the app first, and then initiate a new TCP connection.