This program aims to reproduce the behaviour of monome's serialosc, but with a launchpad instead.
The goal is to expose a very monome like OSC API, and extend it with launchpad specific elements : red/green leds with variable intensity, scene and control buttons ...
The launchpad's micro-contoller uses a degraded mode for USB communication, with very poor bandwidth. Moreover, the protocol used by the launchpad in order to communicate with the computer is poorly designed. The result is a crappy refresh rate.
In order to mitigate the problem, linome exploits two functionnalities of the launchpad: fast led update and double buffering. The first allows us to update the 80 RG leds of the launchpad in one batch, doing it with 81 bytes instead of 240. The second allows us to send our 81 bytes of LED data, then update the 80 LEDs all at once.
After a bit of testing, it looks like linome gives you a steady 11hz refresh rate of the complete launchpad. Because of the use of fast update + double buffering, it also means that LED flashes shorter than 0.08 second might not be displayed at all: the LED status is changed and reverted in linome before it gets to send it to the launchpad in a fast update.
The reference implementation: http://monome.org/docs/tech:osc
Implemented:
/sys/host s: set the destination host for OSC messages/sys/port i: set the destination port for OSC messages/grid/led/set x y s/grid/led/all s
Launchpad specific:
/scene/led/set y s/scene/led/all s/ctrl/led/set x s/ctrl/led/all s
- unless you have set the permissions properly, this program needs to run as root in order to access the launchpad in rw mode.
- when the launchpad is connected, alsa automatically claims the device,
preventing linome to claim it. Right now, the only solution I found to this
problem is to run
modprobe -r snd-usb-audioto kick alsa out of the way.
- extend the API to handle RG LEDs
- using fast LED update only when it is necessary ? It might improve performance.