[maemo-users] [maemo-users] Bad Freedom Input keyboard or poor kbdd driver on N800?

From: centipede centipede at takhis.net
Date: Mon Feb 12 15:56:03 EET 2007
>> On 10/02/07, centipede <centipede at takhis.net> wrote:
>>> I almost has to punch down the keys
>>> and hold them for a short while. The keys seem to soften up a bit, when
>>> used. But still a lot of keypresses are missed. I've watched the
>>> output of
>>> kbdd in the shell, and it seems like the driver skips more keys the
>>> faster
>>> I type.
> Are you sure keypresses are lost or they are simply received too late?
> If they are really lost this is probably something on lower bluetooth
> level in n800 or in the keyboard (can you try fresh batteries?). kbdd
> uses serial rfcomm connection which should be reliable like TCP socket
> (i.e do not loose random bytes).
> http://www.palowireless.com/infotooth/tutorial/rfcomm.asp#Reliability
> Also make sure you don't have more kbdd executables running or anything
> else that could steal data from same /dev/rfcommX device. I'm not sure
> this can happen but just in case.

They are lost, I'll vouch for that. No simultaneous instances running, but
clever of you to spot that possibility.

Funny you mention the bluetooth stack. By now I have disemboweled the kbdd
driver, which after all just opens a serial connection to /dev/rfcommN.
I've played with the baud-rate - slower or faster - but not really any
other settings. No gain. I've also tried to make a tweaked version that
remembers key-presses. If a key-release arrives without a preceding
key-press, both a press and a release is fired. That didn't help anything.

By now I suspect the rfcomm layer. First I couldn't find the code in
Bluez' WebCVS. Then I learned to look under "dead files" for code older
than 3-4 years (!). Hope it's not a sign...

My current hypothesis is that the lag-situation is part of the problem. It
may fool the bluetooth stack, as if the keyboard and the driver needs to
negotiate before accepting another keystroke. "Is that an S-up?", "Yes, it
is a T-down", "???? never mind. T-up you say?".
When I start to write, the first 5-10 keys come through rather nicely. But
there is a (subjectively measured, of course) slight tendency towards
loosing keys once one key makes trouble. Like it comes out of balance.

Sorry for my poor laymans description...

Rene Jensen

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