[BRLTTY] TSI braille display protocol

[Felix G.]

Hello Mario,
if your goal is to emulate a Bluetooth Braille display for
communication with iOS, I suggest you go with the HID Braille usage
page. We've had good results with it, and it can at the same time
become a reference implementation for testing against other HID
Braillers.
Best,
Felix

Am Mo., 4. Okt. 2021 um 08:36 Uhr schrieb Mario Lang <mlang at blind.guru>:
>
> deniz sincar <dsincar29 at gmail.com> writes:
>
> > Hello. as i don't understand brltty driver code, i want to learn the
> > tsi braille display driver serial communication protocol in a human
> > understandable language.
>
> I am afraid we dont have exhaustive protocol description in human
> readable form.  Use the source is pretty much the way to go.
>
> > for example what is the algorhythm to rase dots 125, 15, 123 and so
> > on. how to empty the braille display.
>
> Both of these questions can pretty easily be answered by
> reading the function writeCells() from Drivers/Braille/TSI/braille.c
>
> It constructs the raw bytes of a write request.
> A header, some length and start offset bytes, and the actual payload
> interleaved with NUL bytes.  If you are writing your code in C, you
> could likely take this function almost unchanged and replace the
> final call to writeBytes with whatever you use to write to the serial
> port.
>
> > i very hardly understand the source code. only what i could do is rase
> > a very strange dot pattern on the first 2 sells of the display.
> > i want to learn the protocol of braille output, and the routing keys
> > because i want to connect it to arduino and output some
> > information. or maybe i could do some bluetooth emulators, or other
> > things.
> > please help me on that, thanks in advance.
>
> As said above, we dont have human readable protocol descriptions in most
> cases.  The code is really the best reference you will ever find.
> Also, I find your question rather vague.  It looks like you are planning to
> do a rewrite of the TSI driver from scratch.  Thats fine if you want to
> do it as an exercise, but I am rather lost on how to help you through
> the process step by step.  Also, is there a particular reason why you
> cant use BrlAPI for your Bluetooth emulator?  I dont see why you should
> need to reimplement the TSI protocol from scratch.
>
> P.S.: I have my own use case for a serial to bluetooth bridge.
> My goal would be to emulate a display which is supported by iOS,
> and bridge from a serial display to an iPad.  I have never tried to
> emulate a bluetooth device on a PC, that sounds like a fun project.
> And it appears it could be useful to others as well.
> Maybe BRLTTY should have such a tool by default?
> Does anyone know which iOS supported braille device is most
> promising/easy to emulate?
>
> --
> CYa,
>   ⡍⠁⠗⠊⠕
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