USB Host?

[widdly]

Is it possible to add USB host support on the LPC17? I've seen some other LPC based projects on the web that have midi usb host features.

I think the seq4lite would be great with one of those usb only mini keyboards like the akai lpk25.

[TK.]

Do you have a link to an open source project which uses the USB host function for USB-MIDI?

Best Regards, Thorsten.

[philetaylor]

Not exactly free but there is the USBHostLite for LPC17xx

http://ics.nxp.com/support/software/usb.host.msc/

The license seems to be a bit ambiguous. It says free to NXP customers for unlimited use with NXP LPC2000 and LPC3000 families but includes an LPX1768 example....

Phil

[TK.]

It doesn't contain a USB-MIDI example - so, no "low hanging fruit" ;)

Best Regards, Thorsten.

[philetaylor]

Ah yes I missed the MIDI bit from your post TK!

I'm not sure how USB Host MIDI would work though as it would need to support a number of different USB MIDI devices to be useful?

I seem to remember this was discussed a few months ago as somebody was looking to do a commercial project with USB Host support....

Phil

[widdly]

Unfortunately it's in japanese but this site is the one I was thinking of. It's based of the USBhostlite examples.

http://www.rjblog.net/archives/2009/e000331.php

translated...

http://translate.google.com.sg/translate?hl=en&sl=ja&u=http://www.rjblog.net/archives/2009/e000331.php&ei=K5S8TtuDMKWH4gTO_ISABA&sa=X&oi=translate&ct=result&resnum=1&ved=0CB8Q7gEwAA&prev=/search%3Fq%3Dhttp://www.rjblog.net/archives/2009/e000331.php%26hl%3Den%26biw%3D1366%26bih%3D704%26prmd%3Dimvns

There is source code included. The source code has a parser for the usb descriptors, checking if they are audio devices with midi streaming. Usbhostlite has an interrupt and a blocking function Host_ProcessTD that fills a buffer from the USB port. Other than the first byte, the buffer is written straight to a serial midi port. The example doesn't have any hotplugging implementation other than exiting if the midi usb is disconnected.

There is a description of the first byte content in the USB midi spec, on page 16...

http://www.usb.org/developers/devclass_docs/midi10.pdf

I'm not sure on the hardware side but perhaps this post might be helpful in setting up the physical USB host port on the LPC1768...

http://knowledgebase.nxp.com/showthread.php?t=2064

I would think class compliant USB-midi support would be the way to go. I imagine support for custom stuff would be a nightmare. Although support for the novation launchpad would be a neat way to add a BLM without all the soldering.

edit..

Actually looking more closely at the code from the japanese site, it doesn't look quite right. The MIDI_ParseConfiguration function is never called. I'm guessing he must have modified the usbhostlite function Host_EnumDev to call MIDI_ParseConfiguration instead of MS_ParseConfiguration.

Edited November 11, 2011 by widdly

[flip]

I would think class compliant USB-midi support would be the way to go. I imagine support for custom stuff would be a nightmare. Although support for the novation launchpad would be a neat way to add a BLM without all the soldering.

Oh wow, this would be the perfect use for my Novation Launchpad. It has only been collecting dust so far :)