[BRLTTY] TSI braille display protocol

[Dave Mielke]

[quoted lines by Songpakorn Punongong on 2021/11/19 at 11:28 +0700]

>The protocol for braille code in Bluetooth strings is very simple. It
>starts with [brl] followed by a hexadecimal number for each column of
>braille stream.

I think it'd be a good idea if you were to add a cell count before the braille cells as that'd allow you to have braille displays of various sizes without altering the protocol. Of course, you should then also have a way to query the cell count.

>Each bit of that number represents each row of braille cells. For example,
>the bluetooth string "[brl]703370337033" will display "LGLGLG" on the
>device.

I think you should be using the official standard for this, i.e. ISO 11548-1. Dot1 is 0X01, Dot2 is 0X02, ..., Dot8 is 0X80. Not only is this a standard, but it's also compatible with the Unicode Braille Patterns row.

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