Re: baum: NVDA does not detect usb-braille

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

(splitting the actually-unrelated questions)

Alexander Epaneshnikov, le dim. 18 oct. 2026 21:52:44 +0300, a ecrit:
> On Sun, Oct 18, 2026 at 06:26:53PM +0200, Samuel Thibault wrote:
> > Ah, that is a requirement of the protocol? Then we need to do that
> > indeed. What is the value of the uint8_t protocol field when it
> > expects to receive 0x01 and 0x84?
> 
> It is 1 (on). For serial displays, NVDA's Baum driver
> (source/brailleDisplayDrivers/baum.py) first sends 0x15 with 0 to make
> sure the protocol is off, then sends 0x15 with 1 twice, "in case the
> display misses the first one". After that it waits for the cell count
> and the device identity. According to the comment in that driver, a
> real display answers only when the protocol goes from off to on. On
> that transition it sends its device identity, its serial number and
> its cell count, and it sends nothing if the protocol was already on.
> NVDA itself only waits for the cell count and the identity.

Does the device sends the cell count first or the device identity first?

Samuel