[BRLTTY] developing a braille display driver for a mobile device

[Mario Lang]

Shiri Azenkot <shiri.azenkot at gmail.com> writes:

> I'd like to develop a mobile device application that interacts directly with
> a Braille display via BlueTooth. To do this, I need to know the protocols to
> use with various Braille displays, starting with the HumanWare Brailliant
> that I have right now. It doesn't look like the protocols are available
> anywhere, though, and there seem to be no Braille Display API's for mobile
> platforms.

Well, I don't know how limited your platform is, but BrlAPI should still
be useable.  So you could run BRLTTY and reuse all the bluetooth
code we've already written, and use libbrlapi to develop your
application.  That app would then be mostly device independant
and you'd not need to reinvent the wheel over and over again.

> BRLTTY developers: How did you figure out how to interact with Braille
> displays?

This really depends on the protocol you're trying to implement,
and how similar the bluetooth protocol is to existing protocols
on other connections (serial, USB).  In the case of bluetooth, most
driver support we've developed simply needed bluetooth specific
transfer functions.  All the devices I know of use the same
byte protocol on bluetooth and serial connections.  So since
we already had the protocol implemented for earier models,
we were able to reuse that code when implementing bluetooth
connectivity.

To answer your actual question, in many cases we've been provided
with manufacturer documentation on direct request, and in
a few remaining cases reverse engineering was used.  In any case,
correct driver support for all display types out there
is a tedious process, if I were you, I'd try to reuse
BRLTTY's existing code and go via libbrlapi.

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