Re: [Libusb-devel] Error sending control message: No such file or directory

[Alan S. <st...@ro...>]

On Mon, 15 Dec 2008, Blaine Booher wrote:

> Hey everyone,
>   This is my first post to the listserv, and I apologize if this is a very easy (and annoying) problem to fix.  I want to make sure that I am understanding the USB Packet information correctly.  The data packet I am sending has been witnessed in several packets, and I believe it is a simple 'ping' packet to ensure that the device is alive and responding.
> 
> I have snooped a device's data packets on the USB Bus.  There is a
> packet that I would like to send using the usb_control_msg.  (I am
> technically doing this in pyUSB, but I dont think this is an issue
> with pyUSB more than an issue with my understanding of libUSB).  I am
> under the impression that I want to send 'RequestType' 0x22,
> 'Request' 0x09, 'Value' 0x02, and Index 0x01 (See data attached).

>   When I issue the following command, I get 'No such file or
> directory'.

This means that the command timed out and was cancelled.

>  However, when I change 0x22 to something else like 0x21,
> I can successfully send the command, but brick my device.  I have to
> let the battery drain and reset before I can try again.
> The issued command:  is my device that has successfully been opened by libusb)
> >>> A1=(0x02,0x02,0x95,0x95,0,0,0,0,0,0,0,0,0,0,0,0)
> >>> u.handle.controlMsg(0x22,0x09, A1, 0x02, 0x01)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> usb.USBError: error sending control message: No such file or directory
> 
> And finally, the USB Data that leads me to believe this is accurate:
> [33] URB_FUNCTION_CLASS_ENDPOINT 20081106085253.603 (+54947)
> Transfer flags: 0x00000000 (USBD_SHORT_TRANSFER_OUT)
> Transfer buffer length: 8
> Bytes transfered: 02 02 95 95 00 00 00 00 (......)
> Request type reserved bits: 22
> Request: 09
> Value: 0200
> Index: 0001
> 
> Data returned from Device:
> [33] URB_FUNCTION_CONTROL_TRANSFER (SUCCESS/0x00000000) 20081106085253.603 (+0)
> IRP status: 0x00000000 (STATUS_SUCCESS)
> Pipe handle: 0x87E3DC88
> Transfer flags: 0x0000000A (USBD_SHORT_TRANSFER_OUT, USBD_SHORT_TRANSFER_OK)
> Setup packet: 22 09 00 02 01 00 08 00 (".......)
> 
> Suggestions? Hints? Thank you in advance

You forgot that USB is little-endian.  The Value argument should be
0x0200, not 0x02.  Also, your buffer should be only 8 bytes long, not
16.

Alan Stern