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Re: sending vendor specific commands to mass storage device

At 11:01 AM -0700 10/18/05, bert wrote:

yes, I think you're right. I should probably make a
composite device where interface 0 is mass storage and
interface 1 is HID. Will this work fine on OSX?

I just answered this on the USB-if's discussion, but yes it does work. I've done it, at least during development, we haven't shipped a device like that.

> At 3:25 AM -0700 10/18/05, bert wrote: 

 > >I'm investigating whether to use HID or Mass storage
 > >for my device hardware (audio player). Currently it is
 > >a HID device but I need mass storage functionality to
 > >transfer files to the memory of the device, so I'm

 >thinking of switching to that class.
 >

 > >However, I still need to send device-specific commands
 > >such as 'adjust volume'. How do I do this from an
 > >application without writing drivers?

I just noticed this part. We use separate configurations for this. The problem is a resource contention issue, the player application on the device and the host can not concurrently access the disk. With separate configurations you can make it either a disk, or a HID device so the player can be controlled. Switching between modes is a challenge though, particularly on desktop OSs (ie Mac or Windows).

You should be able to do this with a composite configuration, you just need to get the host to give up use of the disk. We do this by "ejecting" the media, the OS sees the device as a device with removable media and we tell it the media has gone away. That's how you can be charging your iPod from you computer while still using the front panel controls. We don't use HID for control in this circumstance, but it should be possible.
--
Barry Twycross
email@hidden
---
USB, it's not a Dyslexic BUS. (Thanks to TC.)
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 >Re: sending vendor specific commands to mass storage device (From: bert <email@hidden>)



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