Wednesday, June 11, 2008

Servo Car [ Sun SPOT app ] (8)

Let's glance over servocar-spots codes from here. First of all, check out source codes for release 1.0.0 as the following (For this, you need to have a subversion client installed on your computer and an account for, so please prepare both of them if you don't have).
$ mkdir work; cd work
$ svn co servocar-spots --username <username>
You can, of course, check out sources from trunk, but I'm explaining the details based on this release (1.0.0).

Then, build & deploy two Sun SPOT applications - one is for a remote controller named "ServoCar-Controller" and the other is for an actuator of servos named "ServoCar-OnCar".
$ cd servocar-spots/ServoCar-Controller
$ ant deploy
$ cd ../ServoCar-OnCar
$ ant deploy
Next, let's look at the ServoCar-Controller codes, especially related to Sun SPOT networking & accelerometer on EDemoBoard.

Tuesday, June 3, 2008

Servo Car [ Sun SPOT app ] (7)

Sun SPOT application (MIDlet) class has to extend "javax.microedition.midlet.MIDlet" and its life cycle begins from startApp() method.
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
// ...
public class SunSpotApplication extends MIDlet {
// ...

protected void startApp() throws MIDletStateChangeException {
System.out.println("Hello, world");
// ...
To rotate a servo with Sun SPOT, you only have to write the following 2 lines.
Servo serv0 = new Servo(EDemoBoard.getInstance().getOutputPins()[EDemoBoard.H0]);
For the details about "how to move/turn a servo motor", please refer to Servomechanism or Google says a lot about it. Here it's enough for you to know that a servo needs constant "square wave" to move/turn itself and its wave length directly maps to servo angle (or velocity for continuous rotation servo). A typical servo expects to see a pulse every 20 milliseconds and a 1500 microseconds (1.5 millisecond) pulse will make the motor turn to the 90 degrees (it's called "Neutral" position). Other pulses will do it based on their lengths as follows:
  • 1500 - value: 0 degrees
  • 1500 + value: 180 degrees
and the parameter "value" above may vary per servo, but typically it's from 250 to 500 (you may need to investigate your servo before using it). Servo#setValue(2000) just set this length to 2000 microseconds and keep sending pulse to the servo. It's all about your servo code on Sun SPOT!

If you have written embedded programs, you may notice it is not so easy to write the same program with C. Of course it depends on how many libraries you're provided, but typically you need a lot of include files as well as check how to use registers and command syntax for serial communication. Then, you also need to write a program that bring high a digital port, wait for around 1.5ms, bring low the same port (and loop these procedures for a while). Or even if you can use a bit high level operation like ATmega88 "8-bit Timer/Counter2 with PWM and Asynchronous Operation" to generate PWM (pulse-width modulation), the root complication is not solved as long as you use embedded C.

If you feel this is cool, NOW TIME TO CHANGE YOUR PLATFORM TO Sun SPOT!!

Tuesday, May 27, 2008

Servo Car [ Sun SPOT app ] (6)

Let's write a very simple Sun SPOT program for the servos here. We can begin it with the "SunSpotApplicationTemplate" project in ${SUNSPOT_DIRECTORY}/Demos directory (${SUNSPOT_DIRECTORY} is usually "C:\Program Files\Sun\SunSPOT" on Windows, but if you are true to my previous blog entry, it may be "C:\Sun\SunSPOT").

If you haven't had the Demos yet, you could also download it from the web site as we did before (see installing Sun SPOT SDK). Here is a quick summary to install Demos:
  1. access and click the Sun SPOT icon to launch Sun SPOT Manager tool
  2. Select "SDKs" tab
  3. Click "Demos" icon on the bottom-right corner (under Available SDKs)
  4. Press "Install" on the "Demo Installer" panel
Once you got it, please copy ${SUNSPOT_DIRECTORY}/Demos/CodeSamples/SunSpotApplicationTemplate directory into your working directory.
$ mkdir ~/work
$ cp -r ${SUNSPOT_DIRECTORY}/Demos/CodeSamples/SunSpotApplicationTemplate ~/work/ServoTest
$ cd ~/work/ServoTest
Then, modify the code src/org/sunspotworld/demo/ with your favorite editor as follows:
  1. remove the lines from L.56 "long ourAddr = .." to L.66 above "notifyDestroyed();"
  2. add the following code (add bold lines to your code)
public class SunSpotApplication extends MIDlet {
private static final int CENTER = 1500;
private static final int RANGE = 1000;

private ITriColorLED [] leds = EDemoBoard.getInstance().getLEDs();

protected void startApp() throws MIDletStateChangeException {
System.out.println("Hello, world");
new BootloaderListener().start(); // monitor the USB (if connected) and recognize commands from host

EDemoBoard demo = EDemoBoard.getInstance();
Servo serv0 = new Servo(demo.getOutputPins()[EDemoBoard.H0]);
Servo serv1 = new Servo(demo.getOutputPins()[EDemoBoard.H1]);

for (int i = 0; i < 4; i++) {
int r = (i % 2 == 0) ? RANGE / 2 : -RANGE / 2;
serv0.setValue(CENTER + r);
serv1.setValue(CENTER - r);
System.out.println("serv0 value: " + serv0.getValue());
System.out.println("serv1 value: " + serv1.getValue());

notifyDestroyed(); // cause the MIDlet to exit

Then build your project with "ant jar-app". This command compiles all the codes under the project and create jar file under "suite" directory.
$ ant jar-app
$ ls suite
Let's deploy this jar file into Sun SPOT Servo Car (configured before) and run the application. To do so, connect Sun SPOT to your PC via USB cable and execute the following commands.
$ ant deploy

Total time: 8 seconds
$ ant run
[java] SPOT Client starting...
[java] [waiting for reset]

[java] Local Monitor (purple-071018)
[java] SPOT serial number = 0014.4F01.0000.01A8

[java] ** VM stopped: exit code = 0 **

[java] Squawk VM Starting (purple-071018)...
[java] [NetManagementServer] starting on port 20
[java] Hello, world
[java] serv0 value: 2000
[java] serv1 value: 1000
[java] serv0 value: 1000
[java] serv1 value: 2000
[java] serv0 value: 2000
[java] serv1 value: 1000
[java] serv0 value: 1000
[java] serv1 value: 2000

[java] ** VM stopped: exit code = 0 **

[java] Exiting





Total time: 14 seconds

If you can watch one servo rotates clockwise (for 2 seconds), counterclockwise (for 2seconds), clockwise (for 2seconds) and counterclockwise (for 2seconds) while the other servo does reversely, your program is now successfully deployed into your Sun SPOT. Next time, let's investigate this code a little more.

Saturday, May 24, 2008

Servo Car [ Sun SPOT app ] (5)

I've written how to install Sun SPOT SDK, but missed a few things to mention. So I'm doing them here.

First of all, the Project Sun SPOT official URL is You can download SDK, tutorials and manuals here. You can also ask your questions at the forum in this site as well as purchase Sun SPOT Java Development Kit. So this is the start point for your Sun SPOT life.

Before installing Sun SPOT SDK on your computer, you need
installed on your computer (See the installation instructions in your Sun SPOT Java Development Kit for the detail).

Now, we've had all stuff, hardware & software, to write a code for the Sun SPOT Servo Car. Next time, I'm planning to begin with a very simple code other than this, but if you'd like to try it in advance, you can freely check out it from

Thursday, May 22, 2008

Servo Car [ Sun SPOT app ] (4)

Software setup

Let's write a first Sun SPOT application for Servo Car! Typically, Java IDE (like NetBeans) is very useful to write a large Sun SPOT application and I usually use it. However, to make things easy, let's begin with minimal developing environment -- Sun SPOT SDK, your favorite text editor & terminal.

Sun SPOT SDK has a color name according to its version. The current stable version (as of 5/23/2008) is v3 ("Purple" release), so let's use this version for the demo.

If you have a Sun SPOT Java Development Kit with Purple SDK CD-ROM, you may install it from CD. Otherwise, you can install SDK from This site keeps many different SDK versions other than Purple (v3) including beta versions, so I recommend the latter and will explain how to install SDK by using this site.

How to install Sun SPOT SDK
  1. access and click the Sun SPOT icon to launch Sun SPOT Manager tool
  2. Select "SDKs" tab
  3. Select purple-071018 (it may be labeled "Purple Beta RC5") from Available SDKs. If you don't see any versions in it, press "Refresh" button under Available SDKs.
  4. Press "Install" and "Sun SPOTs SDK Installer Tool" will be launched.
  5. Accept defaults other than "New SDK Directory Location". If you're a Windows user, it may begin with "C:\Program Files\Sun ..". There is no problem with this to develop Sun SPOT applications. But if you use Sun SPOT emulator, it causes some problems. So change this location ("C:\Program Files\Sun ..") to other place (e.g. "C:\Sun .."). For details, please refer to
  6. Press "Install". After installing, press "Done".
  7. You should see the installed SDK on "Installed SDKs" panel.
If you change the "New SDK Directory Location" according to the above procedure, please edit and change "sunspot.home" value to meet your change.

To confirm your installation, connect a Sun SPOT to PC via USB cable , open your favorite terminal emulator and check the following command output.

$ cd $(SDK_DIRECTORY_LOCATION) <- specify your directory 
ant info
[java] SPOT Client starting...
[java] [waiting for reset]

[java] Local Monitor (purple-071018)
[java] SPOT serial number = 0014.4F01.0000.01A8

[java] Application slot contents:
[java] C:\cygwin\home\miyake\tmp\ServoTest
[java] 2350 bytes
[java] last modified Fri May 23 11:58:24 JST 2008

[java] Startup:
[java] Squawk startup command line:
[java] -flashsuite:10900000
[java] -Xboot:268763136
[java] -Xmx:478000
[java] -Xmxnvm:128
[java] -dma:1024
[java] -MIDlet-1
[java] OTA Command Server is enabled
[java] Configured to run the current application

[java] Library suite:
[java] hash=0xa2fb25
[java] Installed library matches current SDK library
[java] Installed library matches shipped SDK library
[java] Current SDK library matches shipped SDK library

[java] Security:
[java] Owner key on device matches key on host

[java] Configuration properties:
[java] spot.external.0.firmware.version: 1.9
[java] spot.external.0.hardware.rev: 5.0
[java] EDEMOBOARD_REV_0_2_0_0
[java] spot.hardware.rev: 5
[java] true
[java] spot.mesh.traceroute.enable: false
[java] spot.ota.enable: true
[java] spot.powercontroller.firmware.version: PCTRL-1.79
[java] spot.sdk.version: purple-071018

[java] Exiting



Total time: 2 seconds

"ant info" checks the connected Sun SPOT information. If you see the same output as the above one, congratulations! Your installation was successful.

Sun SPOT Servo Car codes are now on

I've launched a new project ( on and imported all source codes for Sun SPOT Servo Car into it. Your feedbacks, comments and/or questions would be welcome!

Wednesday, May 21, 2008

Servo Car [ Sun SPOT app ] (3)

Hardware setup (cont'd)


In a standard breadboard the holes of the breadboard are connected underneath. Different sets of holes are connected to each other in a variety of ways. This time I selected a breadboard having the following layout (the holes on the same red lines are interconnected each other) .

A servo has 3 connectors: Vdd, GND and I/O pin. I/O pin is used to send a pulse, so this pin has to be connected to Sun SPOT Hxx (H0 -- H3) pin. Here I choose H0 for the servo of right wheel and H1 for the one of left wheel. For this servo, White line is I/O pin, Red one is Vdd and Black one is GND (see below). Check the spec for your servo.

A battery pack has, of course, two wires + and -, so we need the following connections to make a servo work well with Sun SPOT.
  • battery + <---> servo Vdd <---> Sun SPOT VH
  • battery - <---> servo GND <---> Sun SPOT GND
  • servo I/O pin <---> Sun SPOT H0 (or H1)
How to connect

1. Place 2 headers on the breadboard

2. Connect the first servo to the first header

3. Connect the battery to the breadboard

4. Connect Sun SPOT and the first header on the breadboard (SPOT's H0 to I/O pin, SPOT's VH to Vdd and SPOT's GND to GND)

5. Connect the second servo to the second header. To supply the power to the second servo, you also have to connect two headers as the following (with 2 x orange wires).

6. Connect Sun SPOT and the second header on the breadboard (SPOT's H1 to I/O pin)

7. Finish

Next time, let's write a simple program for those servos.

Tuesday, May 20, 2008

Servo Car [ Sun SPOT app ] (2)

Hardware setup

OK, let's begin with hardware setup. For a servo car, we need the following hardware parts:

Those are
  • Sun SPOT x 2 (one on the car and the other for remote controller)
  • breadboard x 1
  • header pin x 3
  • battery (1.5V x 4) and battery pack
  • servo x 2 (each for right/left wheel)
  • jumper wires
You may find some differences between this and the previous one. Yes, the previous one doesn't use a breadboard because many jumper wires on a car look awful. However, to make it easier (in other words, to avoid any solder or other hassles), let's begin with breadboard kit.

You can choose any servo for this servo car demo, but one caveat is that you have to pick up what is so called "continuous rotation" servo. "continuous rotation" means it rotates forever in the same direction (90/180 degrees rotation servo can't be used for this demo. You know why??)

Next time, I'm showing the connections between components.

Monday, May 19, 2008

Servo Car [ Sun SPOT app ]

It's about time for me to write the detail of Sun SPOT applications. iRobot Create + Sun SPOT is such a candidate, but let's begin with a simpler one - "Servo Car". Before delving into hardware & software spec, please see the following video to get a general idea of this demo.

Wednesday, May 14, 2008

OpenSolaris 2008.05

OpenSolaris 2008.05 is now released. I feel it's much easier to install this than to do Ubuntu 8.04 at least on my Laptop because everything works fine including wifi without any hassle. One thing I had to do is to configure keyboard layout (on x window) to swap Caps Lock and Control keys like the following:
  1. migrate to single-user mode

    From GRUB menu, press "e" to enter edit mode and then hit "e" again to edit the "kernel" line. Add " -m milestone=single-user" to the end of the line. Press return and "b" to boot into single user mode


    From command prompt, execute "svcadm milestone single-user" as the root user

  2. After login, execute

    # /usr/X11bin/xrogcfg

    to create & configure xorg.conf. On the GUI panel, do the following to setup keyboard.

    - press keyboard icon located topside -> select "Add new keyboard" -> "config" window appears, then configure

    Keyboard model -> Japanese 106-key
    Keyboard layout -> Japan
    Xkb options -> Control key position -> Swap Control and CapsLock

    - press ok on the "config" window
    - press Quit on the "xorgcfg" window (after doing this, press "yes" to accept default answers for all questions)

  3. execute svcadm to return to the multi-user mode.

    # svcadm milestone all

Wednesday, April 16, 2008

Sun Labs Open House 2008 Report (3)

On the second day (4/10/2008), I attended the following sessions
  • Project Caroline
  • Project Darkstar / Project Wonderland
Here is a summary for the sessions:

Project Caroline

Project Caroline is a hosting platform for development and delivery of dynamically scalable Internet-based services. The platform comprises a programmatically configurable pool of virtualized CPU, storage, and networking resources. Project Caroline helps software providers develop services rapidly, update in-production services frequently, and automatically flex their use of platform resources to match changing runtime demands.

Internet services move from just writing code to "writing AND running" code, but it's really hard to get started. This also means deployment becomes part of developer workflow. To overcome this hard task, Sun Labs has started a research project called "Project Caroline" developing a platform for development and deployment of long-running Internet services.

The main characteristics of this project is "full programmatic control of distributed resources", so you can control resources with Java, JRuby, Perl, Python, etc. For example, a layer 4 load balancer is created as follows by using Java.

scfg = new L4VirtualServiceConfiguration();
new RealService(intAddr.getUUID(), 8080)));
myLB = grid.createNetworkSetting(“myLB”, scfg);

This is another example to create DNS record:

bcfg = new HostNameBindingConfiguration();
myDNS = grid.getExternalHostNameZone().createBinding(
“myDNS”, bcfg);

In this session, there is a demo to control resources for Facebook application. For detailed documentation and samples of this project, please see

Project Darkstar / Project Wonderland

Project Darkstar is a software server, written entirely in Java, to handle massive-scale low-latency applications such as online games. This project is available as open source under GPLv2 license and commercial licenses can be provided. The main goal of this project is to provide an infrastructure that can use available resources very efficiently while giving developers a simple event-driven, single-system view of the world. The current focus of this project has been building out support for multi-node clustering, supporting multiple machines working together to host a single game. For the detail, please visit

Project Wonderland is the Java-based business grade virtual world toolkit. Within those worlds, users can communicate with immersive audio and even share applications, such as web browsers and OpenOffice documents. And Project Wonderland is implemented as serious game on top of Project Darkstar. In this session, an engineer deeply explained how to change Wonderland client design to overcome poor throughput and how to adjust it well to Project Darkstar Server.

Tuesday, April 15, 2008

Sun Labs Open House 2008 Report (2)

In the Sun Labs Open House 2008, there is a Sun SPOT HOL (hands-on lab). This HOL is exactly the same one as the one in JavaOne 2008 that will be held on May 6-9 2008. So if you have a chance to participate in, please try it by yourself. Unfortunately, I wasn't able to take part in the HOL because I had to hear another session at the same time. But the HOL instructor lent me the full kit for this HOL, so I was able to try it after returning to the hotel.

The goal of this HOL is to control a servo (HiTec HS-311 Servo) remotely based on the input from a bend sensor (Flexpoint Sensor Systems bend sensor) like the following video:

The exercise is divided into 5 parts as follows
  • bend sensor hardware setup
  • bend sensor programming on Sun SPOT
  • servo hardware setup
  • servo programming on Sun SPOT
  • networking between 2 Sun SPOTs
and use breadboard to design the circuit. So if you're a software developer, but a beginner for electronic circuit, this exercise is just good for you.

Wednesday, April 9, 2008

Sun Labs Open House 2008 Report

Today is the first day of Sun Labs Open House 2008 and I'm here in Menlo Park to participate in this event. I worked at Sun Labs last June for about 2 weeks to learn and create Sun SPOT demos, so my main purpose here is still for Sun SPOT, however, there were several cutting edge technologies other than it. So I'd like to introduce them as far as I can.

I heard some interesting JVM topics in the morning, but they are all internal-only sessions, so omit the details here. In the afternoon, I attended the following sessions:
  • Sun Small Programmable Object Technology (SPOT)
  • Project Live* [live star]
  • Project Squawk
and watched some demos. Here is a summary:

Sun Small Programmable Object Technology (SPOT)

This is a session to explain Sun SPOT overview & in-the-field including some demos. The agenda is divided into some topics: introduction, hardware, squawk, networking, security, solarium, emulator, in the field and hands on labs.

Sun SPOT device has three layers: battery, processor board with radio and sensor board. Processor board alone acts as a base-station that is connected to PC via USB to communicate with other Sun SPOT. And users can program the device entirely in Java using standard Java tools and/or IDE like NetBeans.

Here is Sun SPOT processor board (what is so called "eSPOT") spec:
  • 180 MHz 32 bit ARM920T core processor (Atmel AT91RM9200)
  • 512K RAM/4M Flash PROM
  • 2.4GHz 802.15.4 Radio Transceiver (TI CC2420)
  • USB interface - mini-b connector
  • Real Time Clock and Power Management Processor (Atmega88)
  • 3.6V rechargeable 750 mAh lithium-ion battery
  • 30 pin high density interboard connector
  • “Java on the metal” - No OS. Squawk VM runs on the bare metal
eDemoboard (sensor board) spec is:
  • 2G/6G 3-axis accelerometer
  • Light sensor
  • Temp sensor
  • 2 push buttons
  • 8 RGB 24 bit LEDS, power/control LED
  • 6 analog inputs readable by a 12 bit ADC
  • 5 General Purpose I/O pins (GPIO) and 4 high current output pins w/ Atmega88 IO processor
You can even make your own Sun SPOT hardware: eDemoboard is just a sample impl. shipped with Sun SPOT developer's kit (see the detail: eBones project).

Sun SPOT developer's kit includes
  • 2 x Full Sun SPOTs with eDemoSensor boards and batteries
  • 1 x base-station Sun SPOT
  • Software (Squawk VM, Java SDK, Netbeans)
  • Other equipments (USB cable, Mounting clips, 2 x wall mounts, 1 x PC board mount)
Sun SPOT radio is based on IEEE 802.15.4 (Zigbee) that is lower cost and power but slower than Bluetooth (802.15.1) or Wi-Fi (802.11). The radio spec is 128-byte packets, ~70m range, 250Kbps, 2.4 GHz and "autonomous mesh networking" extends communication range. It also has easy interface with internet-connected devices via HTTP, TCP/IP* (*TCP/IP implementation is now on going).

The new feature of security aspect (for a forthcoming SDK release) is SSL protocol support. To support SSL, you can just change the current syntax for opening a radio stream connection:

conn =“radiostream://” + addr + “:” + port);


conn =“sradiostream://” + addr + “:” + port);

Sun SPOT SDK also includes a great emulator, so you can try your program even if you don't have any real Sun SPOT!

In the field, Sun SPOT is utilized for several projects like "Project Blackbox" to keep track of conditions present in the box while in transit and Yggdrasil, common framework for data collection.

Project Live* [live-star]

Project Live* explores a new approach to software distribution and configuration of enterprise systems. Live* pushes the traditional installation process back to the factory. Software is distributed in the form of pre-installed immutable file system images that contain major software components, e.g. an OS, a database or an application server. At boot time Live* dynamically composes a collection of such modules into a single virtual software environment. Using a simple file system virtualization technology, Live* makes this composition entirely transparent to all existing software.

Also, similar to software in consumer electronics, Live* consolidates the system customization and configuration settings into a repository separate from the original software. This technology extends the concept of software distribution in the form of ready-to-run images like LiveCDs, with the true modularity and flexibility of customization.

In the demo room, the simplicity of Linux distribution upgrade is demonstrated as follows:
  • A user runs a Red Hat version A (for Live*) on xVM
  • the user makes a lot of customization on this system, e.g. network, font..
  • the user upgrades OS to a new Red Hat version B (for Live*).
  • After installation, he would usually need to reconfigure the above setting, but they are on Live* repository, so the user can use the new system seamlessly.
So, Live* software is even more advantageous when combined with VMware, xVM (Xen) or Virtual Box. It simplifies management while improving robustness and security.

Project Squawk

Squawk is a Virtual Machine designed for resource constrained devices like Sun SPOT (and now being planned to port to LEGO Mindstorms NXT and Custom FPGA). The Squawk
  • Implements J2ME CLDC 1.1/IMP 1.0 Profile
  • Runs on the bare metal (No OS)
  • Designed for memory constrained devices
  • Written mainly in Java
  • Runs multiple applications (isolates) that can be migrated across devices
  • Also runs on Solaris, Linux, Mac and Windows
  • Easy to port
Compared to Standard JVM, a lot of functions on Squawk JVM, e.g. loader, garbage collector, compiler and device driver, are written mainly in Java. With "isolates", One JVM OS process can run more than one applications on it and those applications can share some memories.

Tuesday, April 8, 2008

buziness trip for Sun Labs Open House 2008 (3)

Whenever I stay here at W silicon valley, I always go to "Sushi Boat"@Newark. As the name implies, it's a Japanese-style sushi restaurant though there are no Japanese chefs & staff here.

Monday, April 7, 2008

buziness trip for Sun Labs Open House 2008 (2)

I met again Sun SPOT members@Sun Labs today. It's been a while since I visited Sun Labs last June for 2 weeks to develop Sun SPOT applications. I was writing a Sun SPOT program at Sun Labs in the morning.

At lunch time, I went to Google@Mountain View to meet my friend. From Menlo Park (Sun's office), take 101 South to Rengstorff Ave, turn right at Amphitheatre Pkwy and follow this street (it takes about 10 minutes, so close!). I was treated to Google lunch here and his friend gave me a nice Google T-shirts (thanks a lot!).

In the afternoon, spent my time to continue Sun SPOT programming and talk with Sun Labs members.

Saturday, April 5, 2008

buziness trip for Sun Labs Open House 2008

I've been here in Silicon Valley to participate in Sun Labs Open House 2008. Sun Labs Open House is the annual opportunity to see what's new and exciting research at Sun Labs. It's open not for Sun employees, but for partners & customers.

I arrived at SFO (San Francisco) this morning after 10 hours' flight from Narita. It's 6 or 7 times for me to visit here, but I'm never tired of this place. After renting a car at the airport, I headed to Menlo Park office, then went to the hotel I'm staying. The hotel is W Silicon Valley, which is one of my favorite hotels.

And I'm trying to use this comfortable king size bed right now..

Friday, March 21, 2008

Let's Play with iRobot Create (2)

iRobot Create Open Interface (OI) has many functions, such as controlling LEDs, playing songs and investigating sensors. However, for iRobot Create + Sun SPOT demo, what you need is only
  • Start command
  • Mode command
  • Drive command
"Start" command is a trigger to start OI. iRobot Create has 4 operating modes (Off, Passive, Safe and Full) depending on its control level. In iRobot Create + Sun SPOT demo, you can always use "Full" mode in which you can perfectly contorl iRobot Create, but here I use "Safe" mode which is nearly the same as "Full" mode except having cliff, wheel-drop and internal charger safety features (for detail, see iRobot Create spec).

"Drive" command is used to drive iRobot Create's wheels, which is the main command for this demo. Let's try it with a serial connection + Realterm as previous.

Drive command syntax (in serial sequence) is

[137] [Velocity high byte] [Velocity low byte] [Radius high byte] [Radius low byte]

The range of velocity is -500 to 500 mm/s and that of radius is -2000 to 2000 mm. There are 3 special cases for this radius value as follows:
  • 0x8000 or 0x7FFF: Straight (+ Velocity moves forward and - Velocity moves backward)
  • 0xFFFF: Turn in place clockwise
  • 0x0001: Turn in place counter-clockwise
So, if you want your iRobot Create to perform as the following video,

you need to send the following commands:
  • 128 131 (Start OI and puts the OI into Safe mode)
  • 137 0 100 128 0 (move forward at 100 mm/s)
  • 156 1 44 (until traveling 300 mm (3 s))
  • 137 0 0 128 0 (stop)
  • 155 20 (wait for 20 * 1/10 = 2 s)
  • 137 255 156 128 0 (move backward at -100 mm/s)
  • 156 254 212 (until traveling -300 mm (3 s))
  • 137 0 0 128 0 (stop)
  • 155 20 (wait for 20 * 1/10 = 2 s)
  • 137 0 100 0 1 (move counter-clockwise at 100 mm/s)
  • 157 1 105 (until rotating 360 degrees)
  • 137 0 0 128 0 (stop)
  • 155 20 (wait for 20 * 1/10 = 2 s)
  • 137 0 100 255 255 (move clockwise at 100 mm/s)
  • 157 254 152 (until rotating -360 degrees)
  • 137 0 0 128 0 (stop)
I haven't mentioned the "Wait" command above yet, so let me explain it here. iRobot Create OI has a few "Wait" commands that literally wait a next command until some events occur. "Wait Distance (Opcode: 156)" waits until iRobot Create has traveled the specified distance in mm. So the above "156 1 44" waits 3 seconds when it moves at 100 mm/s. In turn, "Wait Angle (Opcode: 157)" waits until it has rotated through specified agnle in degrees. "Wait Time (Opcode 155)" waits for the specified time.

Apart from that, you may as well have a tool converting a decimal integer to a hex. In Ruby, you can use the following script to investigate the value -100, -300 and -360 we used above.

$ cat conv.rb
#!/usr/bin/env ruby

ARGV.each {|n|
s = sprintf("%.4x", n)
puts "#{n} => #{s} (#{s[0,2].hex} #{s[2,4].hex})"
$ ./conv.rb -100 -300 -360
-100 => ff9c (255 156)
-300 => fed4 (254 212)
-360 => fe98 (254 152)

To execute the above command with Realterm, power on iRobot Create, send "128 131" first and the rest command at once:

137 0 100 128 0 156 1 44 137 0 0 128 0 155 20 137 255 156 128 0 156 254 212 137 0 0 128 0 155 20 137 0 100 0 1 157 1 105 137 0 0 128 0 155 20 137 0 100 255 255 157 254 152 137 0 0 128 0

Until now, we use serial connection with Realterm to test and understand iRobot Create behavior, but it's much interesting to program iRobot Create? OK, let's delve into it from next time.

Thursday, March 13, 2008

Let's Play with iRobot Create

I've written iRobot Create + Sun SPOT demo abstract on the previous two posts. From now, let's delve into iRobot Create internals.

To control iRobot Create, you can use "iRobot Create Open Interface (OI)". iRobot Create has two electronic interface - 7 pin MINI-DIN connector and DB-25 connector to send OI commands. iRobot Create + Sun SPOT demo utilizes 7 pin MINI-DIN to control iRobot Create. Here, let's try some basic OI commands with this built-in serial connection.

Before proceeding, you need to have a serial terminal on your computer (You can download "Realterm" from iRobot Create site if you don't have any one. Realterm is a terminal officially recommended by iRobot).

iRobot Create kit includes a serial cable to 7 pin MINI-DIN and software drivers. To use Realterm (or other terminals), you must remember the serial COM port number to iRobot (on Windows, you can check it from device manager -> port).

After connecting to iRobot, launch Realterm on your computer and go to "Port" tab. Set Baud = 57600 and port number you checked above. Then click "Change" button (without this, your change won't be properly reflected). You can verify the connection by checking that the following output appears on Realterm when powering on iRobot. If you don't, please check if the port number is set correctly.

Each Open Interface command is very simple. Just one byte "Opcode" + some data bytes (0 or more). For example, to turn on iRobot Create's Play LED (which is near ">" button), send

128 132 139 2 0 0

This means
  • 128 (Opcode) = starts the OI
  • 132 (Opcode) = puts the OI Full mode
  • 139 (Opcode) = controls LEDs
  • 2 0 0 (Opcode 139's data bytes) = the first byte indicates which LED you use ("2" = Play LED, "8" = Advance LED (near ">>|" button) or "10" = both of them). the second byte means LED color (0 = green, 255 = red) and the third byte means LED intensity.
To send this command, select "Send" tab, input "128 132 139 2 0 0" in the top left field and press "Send Numbers". After powering on iRobot Create, Power LED lights up and Advance LED blinks. If you see only Play LED lighting up after sending this LED command, your first OI command works perfectly! Congratulations!

Saturday, March 8, 2008

iRobot Create with Sun SPOT (2)

I introduced a brief iRobot Create + Sun SPOT demo on the previous post, so here let me explain a bit deeply how this demo works.

Sun SPOT has many built-in devices, such as LEDs, light sensor, switches, accelerometer and GPIO (general purposes digital I/O) on its eDemo Board and also serves as an IEEE 802.15.4 wireless network node. You can write your programs using these devices as inputs (sensors & switches) and outputs (LEDs) as well as sensor networks with (your favorite!) Java language. It's because Sun SPOT platform has a main processor running the Java VM "Squawk".

I'm planning to write complete details for Sun SPOT on later posts, but here it's enough to go further to know that Sun SPOT has 3D accelerometer, digital I/O pins from/to external devices and IEEE 802.15.4 wireless network capability.

iRobot Create has driving motors and sound devices in addition to LEDs and digital I/O pins. So, now you can imagine how these two can be combined together.
  1. This demo uses one iRobot and two Sun SPOTs.
  2. One Sun SPOT (we call it "sender SPOT") works as a remote controller (you know Wii?) and measures 3D gravity accelerations with its accelerometer.
  3. Then, the sender SPOT tells these values to the other Sun SPOT (we call it "receiver SPOT") via wireless connection.
  4. The receiver SPOT receives these values via wireless connection and calculates which direction & how fast iRobot Create should move.
  5. Then, the receiver SPOT tells its calculation to iRobot Create via serial connection. This interface is called OI (Open Interface).
  6. iRobot Create moves around dynamically .
Next, I'm planning to delve into this iRobot Create OI (Open Interface) without Sun SPOT.

Friday, March 7, 2008

iRobot Create with Sun SPOT

Do you know iRobot Create, Sun SPOT or both of them? If you do, don't you think this combination is pretty cool?

iRobot Create is a derivation of iRobot Roomba which is known as a home cleaning robot. iRobot Create is a developer's version for this cleaning robot and a complete robot development kit that allows you to program new robot behaviors using iRobot Create’s Open Interface (OI).

On the other hand, Sun SPOT (Sun Small Programmable Object Technology) is a small, wireless, battery powered experimental platform from Sun Labs. Sun SPOT greatly simplifies to create a whole new breed of devices (See Sun SPOT for details).

Here, I'll plan to write some internal details of "iRobot Create + Sun SPOT" demo. In this demo, two Sun SPOTs are used; one is for a remote controller and the other is its receiver and controlling iRobot Create behavior (moving, powering on etc.). You can watch a brief demo in the following video: