[PD] USB power off from [shell] for eliminating MIDI interfaceproblems
ingo at miamiwave.com
Wed Oct 16 19:06:51 CEST 2013
I have tried
echo on > /sys/bus/usb/devices/usb1/power/level # turn on
echo suspend > /sys/bus/usb/devices/usb1/power/level # turn off
with different devices (like 4-2 which is the MIDI interface) and I'm always
getting "invalid argument" when I try to use "suspend".
> A while ago a MIDI interface problem came up here that nobody seemed to
> really know about:
> All the sudden huge delays in the range of one or more seconds started to
> happen and then the interface sometimes possibly started playing notes,
> on its own.
> I had experienced this quite a few times with Pd on Windows and Linux and
> already way back (about 25 years ago) with my Akai MPC60 drum sequencer.
> I finally found out what causes it.
> When starting the computer the interface gets powered up as well before
> system is ready to receive any information coming from the interface.
> Therefor the interface keeps every input on the MIDI side in a buffer
> it can transmit it to the USB port.
> From time to time the buffer gets completely overloaded during startup
> receiving too much MIDI what in return makes the interface go nuts! The
> way to reset it is to disconnect it from power.
> Now here is my question:
> Does anybody know how I can power off a USB port (probably using [shell])
> do a reset (USB power off - USB power on) while or after loading the
> I'm on Ubuntu Natty.
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