TT’s Jottings-Blog of VU2SWX

A USB  boot disk is a cool idea. It allows you to carry your favorite operating system in your pocket. Since  all modern PC provide USB boot from BIOS , you can use any computer and work on your on desktop. It is also possible to make data persistent. With ubuntu 9.04 Jaunty Jackalope  it is very easy to make an install disk.   Here is how you can do it.

Get hold of a USB disk which is large enough to hold ubuntu  and your data. I used a 2 GB Jetflash disk.  First, I partitioned it into two using gparted. Both were formatted to fat32 file system. See the figure below. ( You can also choose to install on a single partition).

Next click on System-> Admininstration -Create USB statrup disk. See the Screenshot below.

This will start the aplication unetbootin as shown below.

Click on other button and select the jaunty desktop iso image and then select the USB partition you want to install Ubuntu.

If you want to keep data persistent across  reboots you can check that  option and select the size for data block.  Unetbootin will create a single file named casper-rw on the flash drive and your home directory will be mounted in that file. It is a good idea to keep data persistent as you can walk into any Internet cafe and work with your data.

Click on Make startup disk and wait for some time, your USB boot/install disk is ready.

My summer vacation has just started and I am trying  my hands on several things.. This morning while searching for some components in my junk box, some old audio cassettes came out. In fact, I had a collection of around 200 rare cassettes in the 90s. Most of  them are useless now.

One of the cassettes that came  out was a Jugalbandi recital from Dr. Blamuralikrishna and Pt.Hariprasad Chaurasia .   I remembered the sweet mohanam/bhoopali jugalbandi from the maestros   and instantly decided to recover it and make Mp3s.  My first problem was finding out a cassette player .After some search, I located an old Videocon cassette player.  Its power supply was faulty.. I was able to play the cassette  after 3 hours of hard labour.

Audacity was used to grab the tracks and convert it to mp3. The music is very much mellifluous.  Later ,   I searched   the Internet for  details about the volume.  It is  is listed on music india online. You listen to it here. I could not find any on line shops selling this particular volume.

The  bitx, I  built using the ugly construction method was too ugly to look at.   The board  was rebuilt using Manhattan style construction last week end . Now the board looks tidy and neat. The added advantage is that  I can plug and play with any section.  Individual sections are built on smaller PCBs and all sections are  glued to a larger copper clad sheet.

However, the power output in transmit mode was very low.  Up on investigation , it was noticed  that the band pas filter was not performing well.

This morning, I decided to  experiment with the band pass filter.  My board is based on version 3 schematic of the bitx and the band pass filter was built from old IFTs recovered from a junk radio reviver.  The filter was  not tuning properly. The output at the end of the filter was very low ( 100 mv)  May be the ferrite  used  in the IFT is of inferior quality.

I looked around my junk box and found out some small resistor looking  inductors. I decided to try the  band pass filter  from the original design. This design uses 2 ?h inductors wound on tap washers. Fortunately, I had a few 1?h

I built the circuit as shown below and soldered it to the board.  Oops. The performance went down. I was getting only 50mv  on transmit and the receiver performance also suffered.  Again ,I suspect the  junk box components. I thought of rewinding the coil using tap washer.   Ferrite slugs and torrid cores  are not easily available in this part of the world.

. I looked around the junk box again and found out a set of coils used for 3 band broadcast radio.  I decided to rebuild the  version 3 band pass filter again

The coils were rewound .  I  used 11 turns for the main winding and 3 turns for coupling winding The coil inductance was varying form 2.7 to 1.65 micro henries.  The completed filter was installed and bitx powered up . Now I was  getting around 700mv RF  from the filter stage.  I am yet to test the power amplifier section . I hope I will get 5 watts as advertised.   With the new filter in place the receiver performance has improved tremendously. I can hear lot of stations both on CW and  SSB.

The signal I got while whistling to the mic is also shown below.

As a part of laboratory experiments  for an embedded system course being held at Model finishing School Trivandrum, 2 nos . of mini2440 arm development kits have been purchased by the them  from e bay .  One  of the  kits  is presently with me . My task is to learn it and teach embedded  Linux ( or what ever I learn 😀  ) to the participants of the above course.  I have been playing around it for the past two days and it looks very interesting. See the pictures.

The specifications of the board looks like this.

* Processor — Samsung S3C2440 (ARM920T core) clocked at up to 533MHz

* Memory — 64MB SDRAM (up to 100MHz)

* Flash — 64MB NAND flash; 2MB NOR flash

* Flash expansion — 1 x SD card interface

* Display — LCD controller with four-wire resistive touchscreen interface; optional 3.5- or 7-inch LCD displays

* Networking — 1 x 10/100 Ethernet RJ-45 interface (DM9000 chip)

* WiFi — optional WiFi module

* USB — 1 x USB Host; 1 x USB Slave (B-type interface)

* Serial — 3 x serial ports

* Audio — 1 x stereo audio output interface; 1 x mic interface

* Camera — 1 x 20-pin (2.0mm space) camera interface; optional CMOS or USB cameras

* Other I/O:

o 1 x 10-pin (2.0mm space) JTAG interface

o 4 x user LEDs

o 6 x user buttons

o 1 x PWM control buzzer

o 1 x adjustable resistance, for AD conversion test

o 1 x I2C bus AT24C08 chip, for I2C bus test

o 1 x 34-pin 2.0mm GPIO interface

o 1 x 40-pin 2.0mm system bus interface

* Power — RTC battery; power supply interface

* Clock — internal real-time clock and 12Mhz passive crystal system clock source

* Dimensions — 3.9 x 3.9 inches (100 x 100mm)

* Operating system — Linux 2.6.13;

The board comes with a 4 inch detachable LCD screen. The cost of the board is around $ 89 plus shipping and customs duty. The end price was around Rs 7500 in India. The kit  is preloaded with Linux and the accompaining DVD has all the tools needed for development. The board can also run windows CE,

I have not yet done any serious stuff with the kit.  The user interface is based on qtopia, and it provides  basic  GUI features.

There is handwriting recognition software and an on screen keyboard for data entry.

There are various applications  for common tasks.  I was able to browse Internet and access  the embedded web server  on the board.

I plan to rebuild the system and try to make it boot from a usb stick or SD card.  Let me see how much I can hack on this. Stay tuned for furthur updates.

( This document was written in connection with a one day ubuntu ramastering workshop held at College of Engineering Attingal. See this post)

System Requirement

You need a reasonably  good PC with Ubuntu 9.04 installed. It should have plenty of free space ( say 4 GB ) and minimum 1 GB

Preparing the host system

Create a work directory

# mkdir jaunty

Create the following sub directoires

# mkdir  jaunty/cdrom
# mkdir  jaunty/tmp
# mkdir jaunty/root
#mkdir jaunty/remaster

Mount the jaunty iso image on jaunty/cdrom directory
#mount -o loop jaunty.iso jaunty/cdrom

Copy everything from the cdrom to jaunty/image directory

#cp -r jaunty/cdrom  jaunty/image

Now the  image directory has  the content of your cdrom.

You may refer to this post for an explanation of the contents of the image directory.

Rebuilding the squashfs image.

We are going to rebuild filesystem.squashfs under jaunty/image/casper

Move the filesystem.squashfs image to jaunty/tmp directory

#mv  jaunty/image/casper/filesystem.squashfs jaunty/tmp

Mount the filesystem.squashfs under jaunty/root direct

#mount -o loop jaunty/tmp/filesystem.squashfs jaunty/root

Copy the contents of fileystem.squashfs  to jaunty/remaster

#cp -r jaunty/root jaunty/remaster

Now the jaunty/remaster directory holds the uncompressed root filesystem for your live CD.

Copy resolv.conf and sources.list from the host system

#cp /etc/resolv.conf jaunty/remaster/etc/

Preserve   original sources.list.

#cp jaunty/remaster/etc/apt/soures.list   jaunty/remaster/etc/apt/soures.list.backup

#cp /etc/apt/sources.list /jaunty/remaster/etc/apt/

Make sure that sources.list points to jaunty archive

Now you can chroot to  jaunty/remaster .

#chroot jaunty/remaster

Now run the following ( You are inside chroot )

# mount /proc

# mount /sys

# mount -t devpts none /dev/pts

The above commands mount the respective directories inside chroot.

# apt-get update

Install/remove necessary packages using apt.

Cleanup the unwanted files.

#apt-get clean
#rm -rf /tmp/*
#rm /etc/resolv.conf
#umount -l -f /proc

#umount -l -f /sys

#umount /dev/pts
Exit chroot
#exit

Now replace the sources.list with the original sources.list

#cp jaunty/remaster/etc/apt/soures.list.backup   jaunty/remaster/etc/apt/soures.list

Repack squashfs

# cd jaunty
#mksquashfs remaster image/casper/filesystem.squashfs

Recreate filesystem.manifest& filesystem.manifest.desktop:
Run the following  commands.

# chroot remaster  dpkg-query -W –showformat=’${Package} ${Version}\n’ |  tee image/casper/filesystem.manifest

#cp -v image/casper/filesystem.manifest{,-desktop}

# REMOVE=’ubiquity casper live-initramfs user-setup discover xresprobe os-prober libdebian-installer4′

# for i in $REMOVE
do
sed -i “/${i}/d” image/casper/filesystem.manifest-desktop
done

Recreate md5sum

#cd image && find . -type f -print0 | xargs -0 md5sum > md5sum.txt

Recreate the iso image.

# mkisofs -r -V “Jaunty_remix” -cache-inodes -J -l -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -o ../ubuntu-jaunty-remix.iso .
# cd ..

You can test the new image with virtual box.