linuxaudio.org

On Thu, Jul 12, 2012 at 09:24:34PM +0200, Atte André Jensen wrote:
> I'm trying to use my novation launchpad with chuck. It seems to be

quoted text
> plug/play, at least I didn't do anything except plug and play :-)

>

> However it's acting a bit strange in one regard. The first time I

> handle (read presses from the launchpad and sends something back to

> turn lights on/off) it works as expected.

>

> However the next time I launch my chuck code (without turning off =

> unplugging the launchpad) it doesn't send presses. However the arrow

> up, down, left and right buttons (or at least the up-one, that's

> what I got used to use) works and after pressing it the other

> buttons start sending again.

>

> Every once in a while, it's the other way around, I have to press a

> grid button before the arrow pads start sending.

>

> I checked my chuck code quite thoroughly, and played with various

> things to remedy the problem, but still it might be something I send

> that messes up the launchpad.

>

> Can anyone recognize this behavior? Or the opposite: testify that it

> works without this quirk? Any ideas how to approach the problem,

> narrow down the possibilities and hopefully eventually find a fix?

That is because the LP sends MIDI using running status, and there

is no way to reset it (i.e. force a status byte on the next message),

except a power cycle. The top row uses controller events while the

rest uses key up/down. After re-opening the device the driver code

needs a status byte, and usually using the top row will provide one

(assuming the last event in the previous session was a key one).
Actually *most* events are unambiguous even without a status byte,

but you'd need some ad-hoc code in the driver to exploit that.
Ciao,
--

FA
A world of exhaustive, reliable metadata would be an utopia.

It's also a pipe-dream, founded on self-delusion, nerd hubris

and hysterically inflated market opportunities. (Cory Doctorow)
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