Tamil 99 is the official keyboard recommended by the Govt. of Tamil Nadu for typing Tamil. This is an extended NHM Keyboard layout for Tamil 99 with support for additional characters.
The Keyoard layout is as follows:
The position at /U/ was originally empty. I have mapped U+0BB6 Tamil Letter SHA to that position. Tamil Special Characters have been mapped to their Original Positions. Note that, they might not be supported by all fonts.
For typing Vowel-Consonant combination, type the Consonant Characters, followed by the Vowel.
(e.g) வினோத் should be typed as vsixlf