Re: [Libusb-devel] what does a LIBUSB_TRANSFER_STALL on control transfer mean?

[Peter S. <pe...@st...>]

bob 295 wrote:
> The relevant libusb-0.1 call I'm trying to emulate in async

First do it with sync.


> libusb-1.0 is:
> 
> =========  begin Phidget lib snip =============
>  BytesWritten = usb_control_msg((usb_dev_handle *)phid->deviceHandle,
>                                         USB_ENDPOINT_OUT | USB_TYPE_CLASS |
> USB_RECIP_INTERFACE,
>                                         USB_REQ_SET_CONFIGURATION,
>                                         0x0200, /* value */
>                                         phid->deviceDef->pdd_iid, /* index*/
>                                         (char *)buffer,
>                                         phid->outputReportByteLength, /* size 
> */
>                                         500); /* FIXME? timeout */
> =========== end Phidget lib snip ===========

BytesWritten = libusb_control_transfer(phid->deviceHandle,
  LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE,
  0x09, 0x200, phid->deviceDef->pdd_idd,
  buffer, phid->outputReportByteLength, 500);

As you see the conversion is quite straightforward.

But since the Phidgets devices all abuse the HID class you should
really be using HIDAPI instead of libusb. For some discussion, see:

http://libusb.org/wiki/FAQ#CanIcreateadriverlessdeviceusingHIDclass


> What does it mean when the control transfer returns a
> LIBUSB_TRANSFER_STALL?

That the device does not support your request. See
8.5.3.1 Reporting Status Results page 227 of USB 2.0 spec.


//Peter