Freeze when reconnecting to Brailliant B with new USB driver

[nvaccessAuto]

Reported by jteh on 2015-10-08 23:16
From a HumanWare developer:

In order to fix a problem connection we have with the Brailliant on Windows 10, we decided to use the same USB driver as the BrailleNote Apex for the virtual COM port.

Unfortunately, with this new USB driver, we just found out that NVDA is having a problem when trying to reconnect a second time to the Brailliant. The first time we start or select the Brailliant as the Braille display, it works just fine. But when changing to another display and going back to the Brailliant, or stopping or restarting NVDA, we encounter the issue. NVDA will just “hang” and stop responding. When we unplug the Brailliant, we receive a “Could not load brailliantb display” error message, and then everything goes back to normal and NVDA starts responding again.

...

We found a simple fix for the connection issue, but it requires a little modification of the Brailliant driver in NVDA.

It seems that with our new USB driver that works under Window 10, the Brailliant ignores the first command after a reconnection. By always sending the INIT message twice, we make sure the Brailliant receives the message and reply as expected.

So I suggest you add a second call to self._sendMessage(MSG_INIT) in BrailliantB.py before calling self._handleResponses(wait=True). If not, the process might get stuck on handleResponse.

There is no problem sending the INIT message multiple times.

[nvaccessAuto]

Comment 1 by James Teh <jamie@... on 2015-10-19 05:13
In commit d97f1ec:
Merge branch 't5406' into next

Incubates #5406.
Changes:
Added labels: incubating

[nvaccessAuto]

Comment 2 by James Teh <jamie@... on 2015-11-01 22:23
In commit 453c6f2:
NVDA no longer freezes in some cases when reconnecting to a HumanWare Brailliant BI/B series display via USB.

Fixes #5406.
Changes:
Removed labels: incubating
State: closed