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A laboratory manual for basic analog communication experiments

I was in need of a manual for introducing the analog communication lab experiments to students who had no prior exposure to electronic circuits or analog communication techniques. Since I found no such book which matched my needs, I planned  to prepare a laboratory manual which could help students with the basic understanding of electronic circuit theory to learn and experiment the fundamentals of analog communication techniques.

am6332

The lab manual discusses different methods of implementing analog modulation and demodulation using transistors, switching IC CD4016, opamp IC 741, PLL IC CD4046, timer IC 555 etc along with passive components like  IFTs(Intermediate Frequency Transformers), capacitors and resistors. Introduction of every new circuit component is associated with an appendix section which contains details from the manufacturer’s data sheet. Every experiment is explained with associated circuit diagrams, which were drawn using gEDA schematic editor. Signal waveforms associated with the experiments were simulated in octave and given along with the experiment.

The project is on progress. The current version is available here.

Comments on improvement in conceptual clarity, diagrams, typography or language is most welcome. If you have ideas on expanding the contents with more experiments please let me know.

The github repository of the project is here: https://github.com/kavyamanohar/analogcommunication.

This work is licensed under Creative Commons Attribution-Share Alike 4.0 India License.

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Meera Tamil font in Ubuntu Trusty Tahr

Ubuntu Trusty Tahr is going to be released on April 17th 2014.Meera Tamil

Meera Tamil font, a free licensed unicode font for Tamil will be available in this release.

The font is already available in Debian. In both Ubuntu and Debian you can install the font by

sudo apt-get install fonts-meera-taml

Thanks Vasudev for packaging it for Debian.

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Configurable node logger with winston

For an advanced logging system for nodejs applications, winston is very helpful. Winston is a multi-transport async logging library for node.js. Similar to famous logging systems like log4j, we can configure the log levels and winston allows to define multiple logging targets like file, console, database etc.

I wanted to configure logging as per usual nodejs production vs development environment. Of course with development mode, I am more interested in debug level logging and at production environment I am more interested in higher level logs.

I am sharing my singleton logger instance setup code.

 

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Mediawiki moves to json based localisation file format

Mediawiki is moving from PHP array based localisation file format to json format.

This is based on the RFC: https://www.mediawiki.org/wiki/Requests_for_comment/Localisation_format

A lot of extensions were also migrated to the new localisation format, thanks to Siebrand Mazeland

The json based localization file format was first introduced in our frontend javascript i18n library https://github.com/wikimedia/jquery.i18n

If you are interested in seeing some of the sample json files see https://gerrit.wikimedia.org/r/#/c/122787/ , claimed as “largest patch set in the history of MediaWiki” 

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Brackets, my favorite javascript IDE

I use Brackets for web development. I had tried several other IDEs but Brackets is my current favorite IDE. A few things I liked is listed below

Some extensions I use with Brackets are:

  1. Markdown Preview for easy editing of markdown
  2. Brackets Git for git integration
  3. Themes for Brackets For Monokai Darksoda theme I use
  4. Brackets Linux UI
  5. Interactive Linter realtime JSHint/JSLint/CoffeeLint reports into brackets as you work on your code
  6. WD Minimap for SublimeText like code overview
  7. Beautify for automatic code formatting as you save using jsbeautify

Beautify extension helps me a lot because most of the MediaWiki related code I write needs be as MediaWiki javascript coding convention. I never get it right if I format manually. The convention is a bit different from usual js code formatting. In general you need to use a lot of whitespaces. This extension was using a default jsbeautify formatting configuration and I wanted it to be customizable per project so that I can write my own .jsbeautifyrc file to get my code formatted as per conventions.

There was an enhancement bug for this. I wrote a patch for handling project specific jsbeautifyrc and Martin Zagora merged it to the repo. Here is my .jsbeautifyrc for MediaWiki https://gist.github.com/santhoshtr/9867861

Brackets is in active development and I look forward for more features. The most important bug I would like to get fixed, that all code editors I tried suffer including brackets is support of pain free complex script editing and rendering. Brackers uses CodeMirror for the code editor and I had reported this issue . It is not trivial to fix and root cause is related to the core design. Along with js,css,html, php etc I have to work with files containing all kind of natural language text and this feature is important to me.

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NotoSansMalayalam and nta

NotoSansMalayalam has the following ligature rules for ന്റ (nta)- All uses Akhand Opentype featurenotosansml-nta1

  1. uni0D7B(ൻ) + uni0D4D(്) + uni0D31(റ) => ൻ + ് + റ
  2. uni0D28(ന) + uni0D4D(്) + uni200D(ZWNJ) +uni0D31(റ) => ന്‍ + റ
  3. uni0D28(ന) + uni0D4D(്) + uni0D31(റ) => ന് +റ

notosansml-nta

The first one is what is defined in Unicode chapter 09 section 9.9[pdf]. The second is what Microsoft Kartika used to use for /nta/ as a bug. The last one is what all other fonts follows. If this is what standards can achieve, what can I say?

Spurious glyphs in NotoSansMalayalam

NotoSansMalayalam is a font released by Google internationalization team under noto project. I was checking the glyphs of Malayalam and noted a number of spurious glyphs in the font

notosansml-unwantedglyphs

It is interesting because the font attempted to provide a minimal Malayalam font with reduced glyph set. While attempting that about 10% of the glyphs are either non-existing Malayalam glyphs(Glyphs with dot under consonants) or rarely used glyphs(Glyphs with U+0D62 MALAYALAM VOWEL SIGN VOCALIC L)

Bug filed. It was learned that the last set of glyphs with dots above and below are for Carnatic music notations. They are not defined by unicode, but font used a custom way of representing them with a ligature formed by U+0307.

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Collaboratively edited documentation for Indic font developers

One of the integral building blocks for providing multilingual support for digital content are fonts. In current times, OpenType fonts are the choice. With the increasing need for supporting languages beyond the Latin script, the TrueType font specification was extended to include elements for the more elaborate writing systems that exist. This effort was jointly undertaken in the 1990s by Microsoft and Adobe. The outcome of this effort was the OpenType Specification – a successor to the TrueType font specification.

JanaSanskritSans_ddhrya

The Devanagari ddhrya-ligature, as displayed in the
JanaSanskritSans font.

Fonts for Indic languages had traditionally been created for the printing industry. The TrueType specification provided the baseline for the digital fonts that were largely used in desktop publishing. These fonts however suffered from inconsistencies arising from technical shortcomings like non-uniform character codes. These shortcomings made the fonts highly unreliable for digital content and their use across platforms. The problems with character codes were largely alleviated with the gradual standardization through modification and adoption of Unicode character codes. The OpenType Specification additionally extended the styling and behavior for the typography.

The availability of the specification eased the process of creating Indic language fonts with consistent typographic behaviour as per the script’s requirement. However, disconnects between the styling and technical implementation hampered the font creation process. Several well-stylized fonts were upgraded to the new specification through complicated adjustments, which at times compromised on their aesthetic quality. On the other hand, the technical adoption of the specification details was a comparatively new know-how for the font designers. To strike a balance, an initiative was undertaken by the a group of font developers and designers to document the knowledge acquired from the hands own experience for the benefit of upcoming developers and designers in this field.

glyph-fontforge-meera

Glyphs inside Meera font

The outcome of the project will be an elaborate, illustrated guideline for font designers. A chapter will be dedicated to each of the Indic scripts – Bengali, Devanagari, Gujarati, Kannada, Malayalam, Odia, Punjabi, Tamil and Telugu. The guidelines will outline the technical representation of the canonical aspects of these complex scripts. This is especially important when designing for complex scripts where the shape or positioning of a character depends on its relation to other characters.

This project is open for participation and contributors can commit directly on the project repository.

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Hyphenation in web

This is a follow up of a 4 year old blog post about hyphenation. Hyphenation allows the controlled splitting of words to improve the layout of paragraphs, typically splitting words at syllabic or morphemic boundaries and visually indicating the split (usually with a hyphen).

I wrote about how a webpage can use Hyphenator javascript library to achieve hyphenation for a text with ‘justify‘ style. Along with the hyphenation rules I wrote for many Indian languages, this solution works and some websites already use it. The Hyphenator library helps to insert Soft hyphens in appropriate positions inside the text.

Example showing the difference between Malayalam text hyphenated and not hyphenated. You can see lot of line space wasted with white space in non-hyphenated text

Example showing the difference between Malayalam text hyphenated and not hyphenated. You can see lot of line space wasted with white space in non-hyphenated text

 

More recently browsers such as Firefox, Safari and Chrome have begun to support the CSS3 hyphens property, with hyphenation dictionaries for a range of languages, to support automatic hyphenation.

For hyphenation to work correctly, the text must be marked up with language information, using the language tags described earlier. This is because hyphenation rules vary by language, not by script. The description of the hyphens property in CSS says “Correct automatic hyphenation requires a hyphenation resource appropriate to the language of the text being broken. The user agents is therefore only required to automatically hyphenate text for which the author has declared a language (e.g. via HTML lang or XML xml:lang) and for which it has an appropriate hyphenation resource.”

CSS Example

-webkit-hyphens: auto;
-moz-hyphens: auto;
-ms-hyphens: auto;
-o-hyphens: auto;
hyphens: auto;

Browser Compatibility

  • Chrome 13+ with -webkit prefix
  • Firefox 6.0+ with -moz prefix
  • IE 10+ with -ms prefix.

Hyphenation rules

CSS Text Level 3 does not define the exact rules for hyphenation, however user agents are strongly encouraged to optimize their line-breaking implementation to choose good break points and appropriate hyphenation points.

Firefox has hyphenation rules for about 40 languages. A complete list of languages supported in FF and IE is available at Mozilla wiki

You can see that none of the Indian languages are listed there. Hyphenation rules can be reused from the TeX hyphenation rules.  Jonathan Kew was importing the hyphenation rules from TeX and I had requested importing the hyphenation rules for Indian languages too.  But that was more than a year back, not much progress in that. Apparently there was a licensing issue with derived work but looks like it is resolved already.

CSS4 Text

While this is all well and good, it doesn’t provide the fine grain control you may require to get professional results. For this CSS4 Text introduce more features.

  • Limiting the number of hyphens in a row using hyphenate-limit-lines. This property is currently supported by IE10 and Safari, using the -ms- and -webkit- prefix respectively.
  • Limiting the word length, and number of characters before and after the hyphen using hyphenate-limit-chars
  • Setting the hyphenation character using hyphenate-character. Helps to override the default soft hyphen character

More reading

PS: Sometimes hyphenation can be very challenging. For example hyphenating the 746 letter long name of Wolfe+585, Senior.

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New version of Malayalam fonts released

Swathanthra Malayalam Computing project announced the release of new version of Malayalam unicode fonts this week. In this version, there are many improvements for popular Malayalam fonts Rachana and Meera. Dyuthi font has some bug fixes. I am listing the changes below.

  1. Meera font was small compared to other fonts. This was not really a problem in Gnome environment since fontconfig allows you to define a scaling factor to match other font size. But it was an issue in Libreoffice, KDE and mainly in Windows where this kind of scaling feature does not work. Thanks to P Suresh for a rework on glyphs and fixing this issue.
  2. Rachana, Meera and Dyuthi had wrong glyphs used as placeholder glyphs. Bugs like these are fixed.
  3. Virama 0D4D had a wrong LSB that cause the cursor positioning and glyph boundary go wrong. Fixed that bug
  4. Atomic Chilu code points introduced in Unicode 5.1 was missing in all the fonts that SMC maintained because of the controversial decision by Unicode and SMC’s stand against that. Issues still exist, but content with code point is present, to avoid any difficulties to users, added those characters to Meera and Rachana fonts.
  5. Rupee Symbols added to Meera and Rachana. Thanks to Hiran for designing Sans and Serif glyphs for Rupee.
  6. Dot Reph(0D4E) – The glyphs for this was already present in Meera but unmapped to any unicode point. GSUB Lookup tables added to the glyphs according to unicode specification.

For a more detailed change description see this mail thread. There are some minor changes as well.

Thanks to Hussain K H (designer of both Meera and Rachana) , P Suresh, Hiran for their valuable contribution. And thanks to SMC community and font users for using the fonts and reporting bugs. We hope that we can bring this new version in your favorite GNU/Linux distros soon. Wikimedia’s WebFonts extension uses Meera font and the font will be updated there soon. Next release of GNU Freefont is expected to update Malayalam glyphs using Meera and Rachana for freefont-sans and freefont-serif font respectively. We plan to update other fonts we maintain also with these changes in next versions. There are still some glyphs missing in these fonts with respect to the latest unicode version.

 

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