Re: [Libusb-win32-devel] Return values

[Stephan M. <ste...@we...>]

>=20
> I used the DebugView, but when I use the bulk program, it only returns t=
wo blank lines. When I use the=20
> test program, it returns lots of things. Here are the logs:

Add usb=5Fset=5Fdebug(255) after usb=5Finit() to bulk.c.=20
It should print out some debug information then.
What errors do you see=3F

>=20
>  [...]
>=20
> And here goes the device's descriptors:
>=20

Thanks, that explains why Windows won't configure your four devices:

* each device has two isochronous endpoints (bmAttributes =3D=3D 0x01)
* each of these endpoints has a wMaxPacketSize value of 1024 and
   a bInterval value of 1

According to the USB spec (section 9.6.6) your four devices would require
the following bandwidth to operate (I assume that your devices are high-sp=
eed USB):

* interval: bInterval =3D=3D 1  =3D> 2^(bInterval - 1) * 125=B5s =3D> 125=B5s
* bandwidth of one endpoint: 1024/125=B5s * 1000 =3D 8Mbytes/s
* bandwidth of one device: 8Mbytes/s * 2 =3D 16Mbytes/s
* bandwidth of four devices: 64MBytes/s !!

One single host controller just can't handle this amount of data.
That's why Windows refuses to configure more than two devices. =20
But it should work if you spread your devices across multiple host
controllers.

Apart from that, your device's firmware is not compliant with
the USB specification. Quote from the spec, section 5.6.3:

"All device default interface settings must not include any isochronous=20
endpoints with non-zero data payload sizes (specified via wMaxPacketSize=20
in the endpoint descriptor).  Alternate interface settings may specify non=
-zero=20
data payload sizes for isochronous endpoints.  If the isochronous endpoint=
s=20
have a large data payload size, it is recommended that additional alternat=
e=20
configurations or interface settings be used to specify a range of data pa=
yload=20
sizes.  This increases the chance that the device can be used successfully=
 in
combination with other USB devices."


Hope this helps,

Stephan


> =20
>=20
>=20
> DLL version: 0.1.12.1
> Driver version: 0.1.12.1
>=20
>=20
> bus/device  idVendor/idProduct
> bus-0/\\.\libusb0-0001--0x0547-0x1002     0547/1002
> - Manufacturer : Micro-Star
> - Product      : USB TESTER
>   wTotalLength:         46
>   bNumInterfaces:       1
>   bConfigurationValue:  1
>=20
>   iConfiguration:       0
>   bmAttributes:         80h
>   MaxPower:             50
>     bInterfaceNumber:   0
>     bAlternateSetting:  0
>     bNumEndpoints:      4
>     bInterfaceClass:    255
>     bInterfaceSubClass: 0
>=20
>     bInterfaceProtocol: 0
>     iInterface:         0
>       bEndpointAddress: 02h
>       bmAttributes:     01h
>       wMaxPacketSize:   1024
>       bInterval:        1
>       bRefresh:         0
>       bSynchAddress:    0
>=20
>       bEndpointAddress: 04h
>       bmAttributes:     02h
>       wMaxPacketSize:   512
>       bInterval:        0
>       bRefresh:         0
>       bSynchAddress:    0

>       bEndpointAddress: 86h
>       bmAttributes:     01h
>       wMaxPacketSize:   1024
>       bInterval:        1
>       bRefresh:         0
>       bSynchAddress:    0

>       bEndpointAddress: 88h
>       bmAttributes:     02h
>       wMaxPacketSize:   512
>       bInterval:        0
>       bRefresh:         0
>       bSynchAddress:    0
>=20

=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F
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