Arduino Uno and DHT11 basic temperature-humidity sensor

It is easy integrate DHT11 temperature and humidity sensor with Arduino Uno board. You can find enough resources in the web how to connect DHT11 with Arduino.

Measured temperature and humidity can publish to a Web via APIs supported by

You can find the working code in the Github.


How to fix Arduino porgram upload issues with Ubuntu

When you upload the program to Arduino UNO board you may get an error saying

Serial port ‘/dev/ttyACM0’ not found. Did you select the right one from the Tools > Serial Port menu?

This error occurs when user do not have write privileges to device /dev/ttyACM0. User can fix this issue by giving enough rights to user or simply give all writes to the device. ( chmod  777 /dev/ttyACM0 [this is a hack ;)])

Apache Hadoop 1.0.0 released

Apache Hadoop 1.0.0 released. Release Note

Hadoop 1.0.0 released from 0.20.2xx.x development tree.  There is another new development in Hadoop space with version 0.23.0. New 0.23.0 version contains HDFS Federation and NextGen MapReduce (YARN).

Howto setup Xen 4.1 with Ubuntu 11.10 and run a VM (domU)

Ubuntu 11.10  released with the Linux 3.0.0. Now Linux  has the Xen dom0 support.

setup steps:

1. Install Xen hypervisor

apt-get install xen-hypervisor-4.1-amd64

2. create a domU configuration. ( node0.cfg )

disk = [ 'file:/mnt/vm/xen/vm_images/node0.iso,hda,w',
'file:/media/mnt/vm/xen/iso_files/oneiric-desktop-i386.iso,hdc:cdrom,r' ]

memory=1024 vcpus=1 name="node0"
vif=[ 'type=ioemu,bridge=virbr0' ]
builder = "hvm"
device_model = "/usr/lib/xen-4.1/bin/qemu-dm"
vnc=1 vncunused=1
serial = "pty" # enable serial console
on_reboot = 'restart'
on_crash = 'restart'

3. Start the domain

xm create /pathto/node0.cfg

In the first boot vm boots from cdrom and user can install new OS to vm.
by changing the boot order to boot=”c” user can boot from the hard disk.

4. List running domains.

xm list

Ubuntu 11.10 still need some path fixes to run user domains /vms ( domU ).
You may get an error in your /var/log/qemu-dm-node0.log saying :

Could not read keymap file: ‘/usr/share/qemu/keymaps/en-us’
create symbolic link named qemu-linaro in /usr/share with the name qemu.

For bridge networks default bridge may not include your default NIC.
If your vms ( domUs ) can not communicate with out side networks add
NIC to bridge.

brctl addif virbr0 eth0

Explore Connect Learn WSO2Con 2011

more  Photos and Videos

How to use StratosLive Column ( Family Data ) Store Service.

WSO2 CSS is Column ( Family Data ) Store based on Apache Cassandra . WSO2 CSS  can deploy with any WSO2 Carbon based product and it is available as a service in StratosLive  the PaaS offering of WSO2.

It is very easy to use CSS as a data store with widely available connectors like java based Hector and other thrift based connectors. StratosLive supports Hector API to communicate with the Cassanda based back-end CSS cluster. External applications can use StratosLive PaaS column data store feature with any Cassandra connector.

StratosLive app developers have to use tenant information to authenticate in the connection with CSS data store. Tenant admin can create tenant and authorize the user for data store access.

Check the full sample in OT SVN.

This sample create connection to StratosLive CSS as an external application. It writes random data to StratosLive CSS keyspace and read and output date via stdout.

Instructions to build and run the sample.

Build the project with Maven

Take a copy of the source using svn

mvn clean install

Build the project with dependency libraries

mvn clean assembly:assembly -o

Execute the program

java -jar target/org.wso2.carbon.cassandra.examples-3.2.1-jar-with-dependencies.jar

WSO2Con 2011

WSO2Con 2011 is happening in Colombo Sri Lanka between Sep 12 – 16 at Waters Edge. WSO2Con 2011 is the second WSO2 developer conference and it is more focus on new WSO2 PaaS offering named Stratos and the hosted service StratosLive.

WSO2Con 2011 main conference starts on 13th Sep and ends on 15th Sep. There are pre-conference tutorials and post conference tutorials to get real experience of the WSO2 product stack. Each conference day has two tracks therefore participants can select talks based on the interests.  Check the conference agenda early and select the track.

In this year conference WSO2 customers and partners are presenting their solutions developed with WSO2 products.