Determine file system type

It will avoid me to stackoverflow it every time…

[myuser@myserver ~]$ df -T
Filesystem     Type     1K-blocks    Used Available Use% Mounted on
/dev/sda1      xfs       10473900 2185416   8288484  21% /
...
/dev/sdb1      xfs      209611780  315256 209296524   1% /ephemeral

Works fine unless the FS is not yet mounted…. Otherwise use “file”:

[myuser@myserver ~]$ sudo file -sL /dev/sdb1
/dev/sdb1: SGI XFS filesystem data (blksz 4096, inosz 256, v2 dirs)

Openshift installation on GCE using terraform

I wanted to try to install openshift on a GCE cluster with the official “ansible installer” available on github https://github.com/openshift/openshift-ansible. Nevertheless I did not manage to have the installer creating the VM on GCE and I’m not even sure it is possible (even if it seems based on libcloud). In the meantime I discover Terraform which allow describing an infrastructure in a common language and deploying it on multiple cloud (including GCE and AWS).

Finally I decided to work on a project that will include these 2 topics “Openshift installation with ansible” and “infrastructure creation with terrafrom”.
I did not had to search too long before I found an open source project that aim to do that:
https://github.com/christian-posta/openshift-terraform-ansible

“This repo contains Ansible and terraform scripts for installing openshift onto OpenStack or AWS EC2.

The repo is organized into the different deployment models. Currently tested with EC2 and OpenStack, but can be extended to Google Compute, Digital Ocean, etc. Happy to take pull requests for additional infrastructure.”

That was perfect since I wanted to use GCE. I decided to contribute to this project by adding the GCE support.

Here is an overview of the whole process (more detail on the github project) :

  1. Used Terrafrom to create the VMs cluster on the cloud
    this is based on an Infrastructure file and Terrafrom.
  2. Use Ansible to customize the VMs
    this part use Ansible and an external Opensource project made by cisco to create dynamically a Ansible Inventory file from the Terrafrom files: https://github.com/CiscoCloud/terraform.py. This is not obvious today since the Cisco code is copied in the repo (see my comment later)
  3. Use the Openshift-Ansible installer to install Openshift on these VMs
    This part use the official installer but require a manual action first to create the ansible inventory file.

Remove static “Terraform.py” script

During my changes on the repo I noticed that it was relying on an Cisco project to create an Ansible inventory from the Terrafrom files. Nevertheless instead of cloning the cisco repo (like it is done for Openshift-Ansible Repo) it was committed.
I think it was done like this since the original creator was thinking to modify it later on but for now it prevent us to benefit from the changes done on the official github repository of Cisco. This is particularly true for my usecase since there was a bug preventing to create the inventory file for GCE in the actual version (but fix on the github last versions).
I thus decided first to create a PR to clone the Cisco repo in the procedure and remove the old version which was committed.

https://github.com/christian-posta/openshift-terraform-ansible/pull/1

GCE Terrafrom integration

todo

Artifactory cache (no root/no internet)

Artifactory is a repository manager. It is the one used in my current company to store various packages like RPM/Puppet/Pypi/Vagrant… You can find more documentation on their website:
https://www.jfrog.com/open-source/

This post gathers my note to install an artifactory cache connected to another instance (master instance) to speed up the package retrieval. This procedure is used on a target server where you have no internet connection and no root access.

0/Download

Download Java + Artifactory free on a computer with internet access (or from Artifactory) and transfer them on the target server.

1/Untar/unpack

unzip jfrog-artifactory-oss-4.5.2.zip
tar zxvf jre-8u73-linux-x64.gz

2/Java install

export PATH=/home/sbox/jre1.8.0_73/bin:$PATH
export JAVA_HOME=/home/sbox/jre1.8.0_73

3/Artifactory install

nohup ./bin/artifactory.sh &

4/Add the link to Master repo (to act as cache)

Use the admin UI on port 8080 :

ArtifactoryCache

Be careful when choosing the KEY. I strongly suggest to use the name of the remote repo you want to cache locally otherwise you will have different URL to download from depending on if you want to download from the MASTER or this CACHE.

5/Test it

Curl http://www.<target server IP>/repository/KEY/<stuff>

Stuff is an artifact that should exist on the MASTER artifactory otherwise it will fails…

Electric Train V3

Feel free to have a look on the V2 first:
http://djynet.net/?p=759

The biggest change is in the camera able to follow the phone orientation to update its angle. I also replace the front/rear sensors.

TrainV3

Camera tracking

I used the html5 API to detect the phone orientation:

if (window.DeviceOrientationEvent) {
  // Our browser supports DeviceOrientation
  window.addEventListener("deviceorientation", deviceOrientationListener);
} else {
  console.log("Sorry, your browser doesn't support Device Orientation");
}
function deviceOrientationListener(event) {
  var c = document.getElementById("myCanvas");
  var ctx = c.getContext("2d");

  ctx.clearRect(0, 0, c.width, c.height);
  ctx.fillStyle = "#FF7777";
  ctx.font = "14px Verdana";
  ctx.fillText("Alpha: " + Math.round(event.alpha), 10, 20);
  ctx.beginPath();
  ctx.moveTo(180, 75);
  ctx.lineTo(210, 75);
  ctx.arc(180, 75, 60, 0, event.alpha * Math.PI / 180);
  ctx.fill();

  ctx.fillStyle = "#FF6600";
  ctx.fillText("Beta: " + Math.round(event.beta), 10, 140);
  ctx.beginPath();
  ctx.fillRect(180, 150, event.beta, 90);

  ctx.fillStyle = "#FF0000";
  ctx.fillText("Gamma: " + Math.round(event.gamma), 10, 270);
  ctx.beginPath();
  ctx.fillRect(90, 340, 180, event.gamma);
  
  var aMsg = event.alpha.toString()+"_"+event.beta.toString()+"_"+event.gamma.toString();
  console.log("aMsg" + aMsg);
  doSend(aMsg);
}

Which send the 3 orientation information to the Tornado python server running on the Raspberry pi of the train. First I was doing JSON REST call to send the string containing the information but it was too slow to have the camera moving in real time. This was the perfect opportunity to use websocket for more real time communication.


function onOpen(evt) { 
        console.log("CONNECTED");
        doSend("Hi there!");
    }
    function onClose(evt) { 
        console.log("DISCONNECTED");
    }
    function onMessage(evt) { 
        console.log('message: ' + evt.data);
    }
    function onError(evt) { 
        writeToScreen('error' + evt.data);
    }
    function doSend(message) { 
        websocket.send(message);
    }
function testWebSocket() {
        websocket.onopen = function(evt) { onOpen(evt) };
        websocket.onclose = function(evt) { onClose(evt) };
        websocket.onmessage = function(evt) { onMessage(evt) };
        websocket.onerror = function(evt) { onError(evt) };
}
        

if (!'WebSocket' in window){
    console.log("Sorry, your browser doesn't support Websockets");
} else {
var wsUri = "ws://192.168.10.1:80/ws";
var websocket = new WebSocket(wsUri);
    testWebSocket();
}

Which is received on the server side and put in a variable (see the class Handler_WS) :

    def on_message(self, iMessage):
        """Methode call when the server receive a message"""
        logging.info('Receive incoming message:'+str(iMessage))
        #self.write_message("toto")
        self.aTrainRef._cellAngles=str(iMessage)

This variable is then read every 125ms by the “foo” function:

tornado.ioloop.PeriodicCallback(lambda: foo(aTrain), 125).start()

At the end the real method called is in charge of updating the turret position. The whole stuff is based on an existing framework called servoBlaster which will take care of driving the Servo.

def updateTurretFromScreenAngle(self):
        if (self._cellAngles!=""):
            #Update Gamma
            aGamma = self._cellAngles.split("_")[2]
            aGammaF = float(aGamma)
            aGammaI = int(aGammaF)
            aGammaisNegative = False
            if (aGammaI<0): aGammaI=(aGammaI*-1)-40 aGammaisNegative = True else: aGammaI=140-aGammaI if ((aGammaI>0)and(aGammaI<100)):
                self._turretHeight = 100 - aGammaI
                self.sendPos(ConstModule.CONST_SERVO_HEIGHT,self._turretHeight)
            #Update Alpha
            ...

Servo Blaster is library able to drive Servo on the Raspberry pi using software PWM. It is pretty hard to do since the Pi is not running a real-time OS. It relies on very low level interruption to ensure the timing needed to have a proper PWM are respected. You can have more info on it here:

https://github.com/richardghirst/PiBits/tree/master/ServoBlaster

It basically start a daemon (which I added in the crontab to be launch at boot time) on which you can interact with writing the desired position of each servo in /dev/servoblaster like:

echo 3=120 > /dev/servoblaster 

I also used servo blaster to send PWM info to the motor driver to change the train speed (since this functionality was broken when I moved from Arduino to Rapsberry Pi).

Contact sensors

I replace the old contact sensor by some new sensor able to detect an incoming obstacle before impact.

TrainSensorNew

They are still binary sensors that will turn high if they detect an obstacle but they have a wider range between 2 and 10 centimeters. This allows the train to detect incoming obstacle and stop before hitting it. The sensor is available on ADAfruit:
https://www.adafruit.com/products/1927

Demo

I made some videos on this new version on YouTube:

Code

As always the code is available here:
https://bitbucket.org/charly37/train/overview

Electric train V2

Following the first version of the electric train : http://djynet.net/?p=731

After some weeks of works I’m proud to announce the Version 2 of the electric train:

TrainV2

Wifi capabilities

The train can now be control with Wifi. It creates a wifi hotspot at boot time allowing people to connect to access a UI with some commands. The Wifi hotspot creation is describe HERE

Web

The train now offers a Web UI which allows controlling it and seeing the camera broadcast. The UI is done in Angular JS (with Bootsrap Angular UI). The Web server used to render the page is a python one : Tornado.

In addition of the UI it offers REST API to control the train (which are called today by the UI but could be used for a native Android application). The Web creation setup is detail HERE (TODO).

Embedded camera

The train is now equipped with a camera (the official Raspberry camera). The camera stream is broadcast and available on the train Web UI. The camera broadcast setup is describe HERE

Raspberry Pi brain

I replace the Arduino board with a Raspberry Pi A+. This extra boost of power was needed to broadcast the camera stream and create a wifi hotspot.

UBEC Power source

The biggest surprise I had when creating the new version was lot of unexpected Raspberry Pi reboot. Every time I was starting to move the train the Raspberry Pi was rebooting. I quickly suspect it was due to the motor which either took too much current or create perturbation that the 7805 cannot handle by itself. I done some research to understand how this issue was usually handle in R/C world and find out that they already have the perfect solution : BEC.

It is used to power the command part of the RC model from the same source than the motor. It provides a smooth tension and is able to absorb the impact of the motors on the power source with use of self and capacitor (wikipedia link). Since it is standard component in R/C world you can buy them pretty easily on the Web :

UBEC

The final result is visible in this video : TODO

Raspberry Pi Wifi hotspot

I need my Raspberry Pi to create its own private dedicated Wi-Fi network so that people can connect on it an access some service it provide (like camera broadcast).

To do so I’ve done some search and find out several tutorial to do it (see links at the end of the post). This post is just a sum up of what worked in my case (in case I need to redo it). I strongly suggest to check the links at the end of the article.

The solution rely on 2 software:

  • hostapd
    HostAPD is a user space daemon for access point and authentication servers. That means it can will turn your Raspberry Pi into an access point that other computers can connect to. It will also handle security such that you can setup a WiFi password.
  • isc-dhcp-server
    isc-dhcp-server is the Internet Systems Consortium’s implementation of a DHCP server. A DHCP server is responsible for assigning addresses to computers and devices connection to the WiFi access point.
    Some people use udhcpd which is lighter version

The first thing to do is install the software :

sudo apt-get update
sudo apt-get install isc-dhcp-server hostapd

DHCP configuration

Then configure the DHCP server with 2 files :

  • /etc/default/isc-dhcp-server
#This will make the DHCP server hand out network addresses on the wireless interface
Change “INTERFACES=""” to “INTERFACES="wlan0"”
  • /etc/dhcp/dhcpd.conf

comment the following lines :

option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;

make the DHCP as master on the domain by removing the comment at lines

#authoritative;

define a network and dhcp config by adding the following block (This configuration will use the Google DNS servers at 8.8.8.8 and 8.8.4.4. )

subnet 192.168.10.0 netmask 255.255.255.0 {
range 192.168.10.10 192.168.10.20;
option broadcast-address 192.168.10.255;
option routers 192.168.10.1;
default-lease-time 600;
max-lease-time 7200;
option domain-name "local-network";
option domain-name-servers 8.8.8.8, 8.8.4.4;
}

Network interface

Now that the DHCP server is configured we will setup the network card (wifi dongle in our case) with static IP

edit the file :

/etc/network/interfaces

remove everything related to “wlan0” and past :

allow-hotplug wlan0

iface wlan0 inet static
address 192.168.10.1
netmask 255.255.255.0

and now the last configuration step is the hostapd server

HostApd

create new file:

/etc/hostapd/hostapd.conf

past :

interface=wlan0
driver=nl80211
#driver=rtl871xdrv
ssid=MyPi
hw_mode=g
channel=6
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=raspberry
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

Be aware of the driver choice : nl8021.

Then the last file to configure :

/etc/default/hostapd

Find the line #DAEMON_CONF=”” and edit it so it says DAEMON_CONF=”/etc/hostapd/hostapd.conf”

Don’t forget to remove the # in front to activate it!

Then you can test with :

sudo /usr/sbin/hostapd /etc/hostapd/hostapd.conf

If it does not works with an error related to the driver….you need to DL the one made by adafruit (see llinks at the end)

Extra

To start the 2 services :

sudo service isc-dhcp-server start
sudo service hostapd-server start

and if you want to start them at boot time :

sudo update-rc.d isc-dhcp-server enable
sudo update-rc.d hostapd enable

Useful links found in my research:

Broadcast Raspberry Pi camera

I need to broadcast the stream of my Raspberry pi camera mounted in front of the train. More info on the “train” project here (part1) and here TODO

PHOTO TODO

This is the results of my search on the possible solutions :

motion

more for security or motion detection

with VLC

The camera stream is send to vlc which forward it over the network

raspivid -o - -t 0 -hf -w 640 -h 360 -fps 25 | cvlc -vvv stream:///dev/stdin --sout '#rtp{sdp=rtsp://:8554}' :demux=h264

-Slow, Delay

+Easy

Direct capture with the new recent v4l2 driver

cvlc v4l2:///dev/video0 --v4l2-width 1920 --v4l2-height 1080 --v4l2-chroma h264 --sout '#standard{access=http,mux=ts,dst=0.0.0.0:12345}'

+Easy

-Require VLC

with ffmpeg//ffserver

https://www.ffmpeg.org/

A complete, cross-platform solution to record, convert and stream audio and video.

–The stream is capture and stream by ffmpeg

raspivid -n -vf -hf -t 0 -w 960 -h 540 -fps 25 -b 500000 -o - | ffmpeg -i - -vcodec copy -an -metadata title="Streaming from raspberry pi camera" -f flv $RTMP_URL/$STREAM_KEY

with MJPG streamer

MJPG-streamer takes JPGs from Linux-UVC compatible webcams, file system or other input plugins and streams them as M-JPEG via HTTP to web browsers

http://sourceforge.net/projects/mjpg-streamer/

with gstreamer

GStreamer is a library for constructing graphs of media-handling components. The applications it supports range from simple Ogg/Vorbis playback, audio/video streaming to complex audio (mixing) and video (non-linear editing) processing.

http://gstreamer.freedesktop.org/

RPi caminterface

RaspiMJPEG is an OpenMAX-Application based on the mmal-library, which is comparable to RaspiVid. Both applications save the recording formated as H264 into a file

http://elinux.org/RPi-Cam-Web-Interface

WebRTC UV4L

WebRTC is a very powerful standard, modern protocol and gives a number of nicefeatures

http://www.linux-projects.org/modules/news/article.php?storyid=174

-only works with pi2

picamera

The project consists primarily of a class (PiCamera) which is a re-implementation of high-level bits of the raspistill and raspivid commands using the ctypes based libmmal header conversion, plus a set of encoder classes which re-implement the encoder callback configuration in the aforementioned binaries. Various classes for specialized applications also exist (PiCameraCircularIO, PiBayerArray, etc.)

https://picamera.readthedocs.org/en/release-1.10/install2.html

avconv

avconv is a very fast video and audio converter that can also grab from a live audio/video source. It can also convert between arbitrary sample rates and resize video on the fly with a high quality polyphase filter.

CRTMPServer

http://www.rtmpd.com/

crtmpserver it is a high performance streaming server able to stream (live or recorded)

live555

http://www.live555.com/liveMedia/

Not tested

PiStreaming

https://github.com/waveform80/pistreaming

Not tested


Finally I decided to use “RPi caminterface” which has the best feedback. I confirms it works out of the box (which save me lot of times).
I could maybe migrate to “WebRTC UV4L” if I decide to go to a Pi2 in the future…


 

Here are the links I find during my search :

Electric train hack proto

This will be a very quick post since there is nothing new on this project….except maybe the use of openscad to do the design of the train structure.

Original goal is to have a small electric train running all over the office hanging on the celling. This is the prototype 😉

Train_proto

I simply buy an electric train on Amazon :

http://www.amazon.com/Bachmann-Trains-Thoroughbred-Ready–Scale/dp/B001RG7LDU/ref=sr_1_12?s=toys-and-games&ie=UTF8&qid=1437179429&sr=1-12

Then I rip it apart to understand how it works to be able to hack it.

Train principle

The train itself is very very stupid and is just some metal structure (pretty heavy by the way) with a motor.

Train_rip

The power for the motor comes directly from the rail through the wheels:

Train_wheel

The rails on the other side are smarter since there is a control panel to change the train speed/direction.

Rail_train

The principle is thus very simple…..The command panel generate a different tension in the rail to increase/decrease the speed. It can also invert the tension to go revert.

Hack it

I wanted several things:

  • Possibiility to control the train from phone
  • Train should works without a close circuit (in the office we only have one straigt way).

I decided to put the logic in the train rather than the rail. To do so I used an Arduino Micro (same as leonardo but smaller) with a motor controller and a BT receiver. There is nothing new here that I already done/explain in previous project except the motor controller.

The Bluetooth communication with an Android APP is the same software that the one used in this previous project : http://djynet.net/?p=639

The motor controller is the one of Sparkfun (HERE) and can control up to 2 motors. I used it to be able to change the motor rotation direction and speed (with PWM from arduino). This is indeed mandatory because the train will have to go in the 2 directions due to the linear rail circuit (one strait line).

The rails have now a constant tension of 12V from a AC/DC converter which power all the cards. The train is equipped with 2 sensors at front and rear. They are used to detect collision at the end of rail road and change the motor direction to go reverse

collision_sensor

The program is pretty simple since it just monitor collision sensor to change direction and serial bus for incoming Bluetooth message.

Finally I needed to put all that on the top of the train base with a nice 3D printed support. This was the good opportunity to try 3D printing. I done the design with OpenScad

Thus it might be the application you are looking for when you are planning to create 3D models of machine parts but pretty sure is not what you are looking for when you are more interested in creating computer-animated movies.

OpenSCAD is not an interactive modeller. Instead it is something like a 3D-compiler that reads in a script file that describes the object and renders the 3D model from this script file.

To sum up….you code your design and then compile it to generate the STL file 😉

I just created a basic shape with the place for the sensor at both end and then upload it on shapeways (a cloud 3D printing service).

train_3d_base

It fit perfectly the train and here is the final result once everything is mounted on it:

train_final

All the code (Arduino, Android, OpenScad) is available on my bitbucket account here.

Next step…..why not a camera on the train streaming live 😉

Bluetooth Low Energy device and Android communication

Long time I didn’t post an article since I was busy with my move to Boston…..

I was so tired of having to type my Android Password all the time I wanted to use my phone (when listening to music for example) that I decided to do something about it….. Nevertheless I didn’t want to remove the password protection on my phone since it contains lot of important information.

First I decided to have a look on NFC communication to be able to unlock the phone with a NFC card. I didn’t have lot of success with this lead since the NFC module is stop when the device is locked (as far as I understand).

Then I thought about using Bluetooth communication since I already had some experience on BT communication under android (link). I also wanted to have a look on Bluetooth last version “Bluetooth low energy”. It seems a promising technology (Apple Ibeacon, Smartwatch, Activity tracker…). I finally decided to create a service on Android which will detect the BLE devices in range and depending on that can remove/reset the android security policy. Basically if my BLE device is in range the service will remove the android security policy so the phone will no longer require a password. Moreover as soon as the BLE device is no longer in range the service will revert to the previous security policy (see video for concrete example).

I didn’t focus too much on the hardware part which is simply composed of a BLE beacon. To do it I simply used a Arduino Leonardo and a BLE Arduino shield: http://redbearlab.com/bleshield/

BLE_Ardu

The Arduino code is the example provided in the shield library available here

The Android part of the project is composed of 2 parts: BLE interface and Android Device Policy interface.

BLE interface

The first important thing to understand is that the support of BLE is only working fine with Android > 4.4 (the official doc mentioned 4.3 but some people report issue when trying to use 4.3 and BLE). Be sure to use the API >= 4.4.

There is pretty good tutorial on Google Android Website available here : https://developer.android.com/guide/topics/connectivity/bluetooth-le.html

I mainly follow it (with lot of simplification to kept the only necessary step) to dialogue with my BLE device. It would be useless to describe it here but the process is pretty straightforward :

  • Declare valid permission (some website indicate that the BLUETOOTH_ADMIN is only necessary to turn on/off the BT and thus you don’t need it if the BT is already ON….this is correct for BT but not for BLE. )
  • Activate BT if necessary. Similar to the BT process
  • Scan for BLE devices : Don t forget to stop scanning ASAP otherwise it will empty your phone battery. Implement the scan callback (called every time that the scan finds a device
  • Connect to the BLE : BLE connection is different from the usual BT. There is more granularity in the association process due to the fact that the BLE device can expose several different services with different access level. For example the device could let you access public information without any access check and offer private functionality (like administration) with user access control.
  • Register to BLE change : Once connected we also reegister to the BLE device status changes. This will be used by the process to activate (or not) the Android security policy. This is done by implementing the callback “onConnectionStateChange”
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
                Log.i("MyActivity", "onConnectionStateChange");
                gatt.readRemoteRssi();
                if(newState ==  BluetoothProfile.STATE_CONNECTED) {
                    aDeviceInRange = true;
                    deactivate_lock();
                    Log.i("MyActivity", "Device is in range");
                }
                else {
                    aDeviceInRange = false;
                    Log.i("MyActivity", "Device is not in range");
                    activate_lock();
                }
    
                runOnUiThread(new Runnable() {
    
                    @Override
                    public void run() {
                        Log.i("MyActivity", "scanning");
    
                        TextView t = (TextView)findViewById(R.id.textView4);
                        t.setText("Status : " + String.valueOf(aDeviceInRange));
                    }
                });
            }
    

 Android Device Policy changes

Unlike the BLE connection there is no clear documentation about “how to change android security setting”. If you look for it you will find 2 things : KeyguardManager/KeyguardLock and WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD.

So let’s be clear …. There is no way to do it with the “layout flag”. The best you will achieve is to be able to turn on the phone and display your application but you will not be able to exit your application. If you try to exit your application the OS will ask for the password. That is the best you can do today with this solution.

The other one “KeyguardManager/KeyguardLock” could (or could not) work depending on your luck ! Indeed it has been deprecated since API 13 as explained on the official documentation here : http://developer.android.com/reference/android/app/KeyguardManager.KeyguardLock.html

Hopefully it works fine in my case so I didn’t dig too much for another solution but if it doesn’t works for you I suggest to check the android device administration class available here (but continue reading) : http://developer.android.com/guide/topics/admin/device-admin.html

The lock/unlock code is thus pretty simple with the 2 following functions :

    public void activate_lock() {
        Log.i("MyActivity", "click on activate lock button");
        boolean isAdmin = mDevicePolicyManager.isAdminActive(mComponentName);
        if (isAdmin) {
            boolean result = mDevicePolicyManager.resetPassword("test",DevicePolicyManager.RESET_PASSWORD_REQUIRE_ENTRY);
            KeyguardManager kgManager = (KeyguardManager)getSystemService(Activity.KEYGUARD_SERVICE);
            KeyguardManager.KeyguardLock lock = kgManager.newKeyguardLock(Context.KEYGUARD_SERVICE);
            lock.reenableKeyguard();
        }else{
            Toast.makeText(getApplicationContext(), "Not Registered as admin", Toast.LENGTH_SHORT).show();
        }
    }

    public void deactivate_lock() {
        Log.i("MyActivity", "click on remove lock button");
        boolean isAdmin = mDevicePolicyManager.isAdminActive(mComponentName);
        if (isAdmin) {
            mDevicePolicyManager.resetPassword("",0);
            KeyguardManager kgManager = (KeyguardManager)getSystemService(Activity.KEYGUARD_SERVICE);
            KeyguardManager.KeyguardLock lock = kgManager.newKeyguardLock(Context.KEYGUARD_SERVICE);
            lock.disableKeyguard();
        }else{
            Toast.makeText(getApplicationContext(), "Not Registered as admin", Toast.LENGTH_SHORT).show();
        }
    }

The full code (not sure it include the last changes done just before I move to Boston) available on my BitBucket account here and a demo video is available on youtube here.

Next steps

None ! indeed I just read an article about android 5.0 and this exact functionality has been integrated on the OS itself so my app is no longer useful. The full article is available on TC : http://techcrunch.com/2014/10/28/android-5-lollipop-security-features/ but it solve the exact same problem as you can see from the abstract below :

Lollipop adds some new lock methods that make it easier to keep your 
device secure, which is a huge boon to the overall integrity of the 
platform. The biggest roadblock to mobile device security is actually 
user apathy, which sees people skipping basic security practices like 
implementing a lock screen pin code because it’s inconvenient when 
you’re checking your device every few minutes. Lollipop offers Smart 
Lock to help address this, which uses paired devices to let you tell 
your device it’s okay to open up without requiring a password or 
other means of authentication.