Mindsensors NXTCam v4 User Manual

NXTCam v4 User Guide

What is NXTCam

NXTCam is a real-time image processing engine. Think of
it as a vision sub-system with on-board processor and a
protocol interface that is accessible through a standard
NXT sensor port. This interface provides high-level,
post-processed information of the image NXTCam sees.
The processed information contains the bounding box
coordinates of the objects of interest in view of NXTCam,
in line tracking mode, this information contains
coordinates of line segments.

NXTCam does not send the image itself to NXT, however connecting NXTCam to a
PC with USB cable, and using a Viewer and Configuration software, you can see the
image on the PC.

NXTCam-v4 is compatible with NXTCam-v3 software and libraries.

NXTCam Specs

• Track up to 8 different colorful objects at 30 frames/second

• Configure the NXTCam using USB interface on Windows XP, Windows Vista.

• Supports two tracking modes: Object tracking and Line tracking.

• Provide real-time tracked object statistics (number of objects, color of

objects, bounding box coordinates or line coordinates) through a standard
NXT sensor port.

• Tracked image resolution of 88 x 144 pixels at 30 frames/second

• Perform full-resolution (176 x 144) pixels color image dumps to PC via USB

port.

• Maximum power consumption (42 mA at 4.7 V)

• Uses NXT compatible I2C protocol for communications.

• Supports Auto Detecting Parallel Architecture (ADPA) for NXT sensor bus.

This means that NXTCam can coexist with LEGO or third party digital
sensor on the same NXT port. ADPA support enables user to employ several
sensors on the same port without the need of external sensor multiplexer,
reducing the overall size without compromising the functionality.

What you will need before using NXTCam

Connector Cables

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For runtime operations (on the robot, in autonomous mode), the NXTCam connects
to NXT on a sensor port using a standard connector cable that comes with NXT (the
one with jacks similar to phone jacks).

For offline operations (for programming and configurations), NXTCam connects to
PC using mini-USB cable. (This is in addition to the cable
you would use to connect NXT to your PC). Adjacent
picture shows the mini-USB connector you would need on
your USB cable, this connector is commonly used for
digital cameras. If you need to acquire a cable separately, it should be a ‘5 wire’
cable.

USB Driver installation

In order for NXTCam to work properly, you will need to install USB drivers for your
operating system. Currently support exists for:

 Windows XP (i386 and AMD processors)
 Windows Vista (i386 and AMD processors)
 Mac OS X v10.4.10 (PowerPC G4)

Download the drivers and installation instructions from following location:

http://www.mindsensors.com/NXTCam_Driver_Installation.htm

Viewer and Configuration Software

To see the picture that’s in the field of view of NXTCam, capture that picture for
analysis and configure the Colormaps for onboard processing, you will need to install
and use Viewer and Configuration software on your PC.

Download Viewer and Configuration software for your operating system from
following location:

For MS-Windows XP/Vista: http://nxtcamview.sourceforge.net/ (developed by Paul
Tingey)

For Mac (10.5 or order):

http://www.mindsensors.com/index.php?
module=documents&JAS_DocumentManager_op=viewDocument&JAS_Document_id=
53

For Mac 10.6 or newer:

http://www.mindsensors.com/index.php?
module=documents&JAS_DocumentManager_op=viewDocument&JAS_Document_id=
180

For Linux:

https://github.com/jgraef/aNXTCam (developed by Janosch Gräf)

Programming Environment(s)

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NXTCam is supported for use in NXT-G using a custom block. Download the block
from following URL: http://www.mindsensors.com/NXTCam_NXT-G_Block.htm

This block provides functionality for tracking objects based on the Colormaps
downloaded on NXTCam.

Follow the installation instructions provided at this URL to install the block.

Note: While using with NXT-G, ensure to use firmware version 1.05.

LeJOS API’s are available at:

http://lejos.sourceforge.net/p_technologies/nxt/nxj/api/lejos/nxt/NXTCam.html

RobotC API’s are available at:

http://www.mindsensors.com/index.php?
module=documents&JAS_DocumentManager_op=viewDocument&JAS_Document_id=
50

NXC/NBC Library functions are available at:

http://www.mindsensors.com/index.php?
module=documents&JAS_DocumentManager_op=viewDocument&JAS_Document_id=
57

Connecting NXTCam

Wiring for NXTCam

NXTCam may be connected to any of the sensor ports of NXT using standard NXT
connector cable. In your program, select the appropriate port number to which
NXTCam is connected.

WARNING

Do not connect the NXTCam to any motor port, as the voltage applied by the motor
port may damage the electronics of NXTCam.

During offline operations, such as programming and configuration, NXTCam must be
connected to PC (using USB cable) as well as NXT (using standard NXT connector
cable) while NXT is powered ON.

During runtime (or autonomous) operations on NXT, the USB connection to PC must
be removed.

NOTE: While NXTCam is connected to NXT as well as PC, the PC communication
takes priority over any other communication.

In other words, while NXTCam is connected to PC as well as NXT, if you run a
program on NXT, it will not be able to talk to NXTCam.

Mounting NXTCam on your contraption

The holes on the NXTCam enclosure are designed for tight fit of
Technic pins (or axles) with ‘’ cross section. The holes however
are not designed for repeated insertions/removals of these pins.

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To mount NXTCam v2 on your contraption we suggest that you use two dark gray
‘Technic Axle 3 with Stud’ as shown.

Insert axles from the front (lens side) of the NXTCam and secure with a bushing on
the back or mount it on your contraption directly.

Alternately, you may use blue ‘Technic Axle Pin with Friction’, as shown.

While disassembling contraption, leave the axles and/or pins on NXTCam.

LED on NXTCam

The LED on NXTCam blinks initially when NXTCam is booting up
(when power is connected through USB port or NXT Sensor port).
During the normal operation the LED may blink occasionally.

Configuring NXTCam Colormaps using NXTCamView

What’s a Colormap?

The objects of interest are recognized by NXTCam by matching the stored color
values with the captured image. To do that, color values of the objects of interest
need to be stored in NXTCam’s memory. These color values are known as Colormaps.

NXTCam can store up to 8 Colormaps and provide processed information of the
objects matching those Colormaps.

Default Object Colormap

The NXTCam is shipped with a default Colormap to track a light source (white light).
Download a test program or write a test program, and try tracking a light source.

Objects of interest

Below are screen dumps of NXTCamView software, showing objects of interests and
their tracking information.

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The top left window in the picture below shows the field of view of NXTCam.
The objects of interest from this view are the red and blue pens. In the object
tracking mode, the bounding box coordinates are returned, as shown:

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