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usb communicatioons

Posted on 2012-03-17
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Last Modified: 2012-03-17
I would like to write a java routine to send and receive from a usb port.  I have been looking at several sites and it appears to more than a trivial task.  I did run into this response to the question on a site and am curious about the statement concerning mounting it and writing to it like a drive.  Anyone have any insite on this approach and maybe a little explanation as to how to do it?

The following is the posting from the other site:

if you are looking to directly build something in low level you can see http://www.beyondlogic.org/ for information about specs...

If you want some examples of code you can look at http://www.libusb.org/wiki/libusb-1.0 ... It's in C though.

If you just want to communicate with the USB in linux, you can just have linux mount it and write to it as a regular drive without having to deal with all the other stuff...
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Question by:sargent240
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Dave Baldwin earned 500 total points
ID: 37733777
USB is a network interface, not just a port.  Most devices require low level drivers.  Generally speaking, I don't believe java is suited to that.  So for most devices, you need to talk to the driver and not the USB 'port'.  If it 'looks' like a disk drive to Linux, you can address it that way.
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by:sargent240
ID: 37733782
Your saying it does not look like a disk drive, right?
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by:sargent240
ID: 37733785
I'm trying to control a music keyboard with a computer and can do it with the rs232 port.  When I plug in the usb to midi cable "midi1" appears in the dev directory.
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by:sargent240
ID: 37733802
Can you tell me what value there is in the "midi1" entry in the /dev directory when I plug in the usb to midi cable if any?
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by:Dave Baldwin
ID: 37733816
I suggest you try to send your data to the 'midi1' device like you would a file.  That would be standard practice in Linux.  Open, read, write.  You should get the same responses as from your RS-232 version I would think.  Just a different interface.
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Author Closing Comment

by:sargent240
ID: 37733864
Again Thanks.
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Author Comment

by:sargent240
ID: 37733875
I have one other question and I will open a new question if you like, but how is the baud rate controlled if it is handled like a file?
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by:Dave Baldwin
ID: 37733976
Midi only operates at 31.5 kBaud as far as I know.  You don't have to set it for a USB MIDI interface.  This http://www.faqs.org/docs/Linux-HOWTO/MIDI-HOWTO.html seems to be the best Linux MIDI resource I can find at the moment.  Many older links for this subject are dead.
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