Re: [libusb] External: - Re: Question - "libusb: error [winusbx_set_interface_altsetting] SetCurrentAlternateSetting failed: Insufficient system resources exist to complete the requested service."

[Tim R. <ti...@pr...>]

Fourcade, Pierre wrote:
> Hello,
> We are indeed using an isochronous endpoint in our alternate setting. 
> We are working on a USB 5 Gb/s connection, and the endpoint is 
> configured as follows:
>
>   * Maximum packet size: 1024
>   * Burst size: 12
>   * Number of iso-packets: 3
>   * Service interval: 1 uFrame
>
> Theoretical throughput is then around 2.4 Gb/s, so we should be within 
> the allowed bandwidth.


Well, mostly.  You're asking for 300 MB/s.  The total bus capacity after 
encoding is about 500 MB/s, but only 80% of that bandwidth is allowed to 
be allocated to reservations for interrupt and isochronous pipes.  Mice 
and keyboards also have reservations, although USB 2 traffic travels on 
different wires from USB 3 traffic.


It could just be a host controller failure.  Do these errors happen on 
the same types of computers?

-- 
Tim Roberts,ti...@pr...
Providenza & Boekelheide, Inc.