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

[Fourcade, P. <Pie...@sm...>]

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. Additionally, no other USB devices (besides a mouse and a keyboard) are connected.
The issue is that if it were asking for more than the possible bandwidth, this should happen systematically and be reproducible. Here, it is basically that one day we will just plug in a new device, and the issue will be present. Even previous devices that were correctly accessed are now presenting the issue.

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On 10/15/24 1:45 AM, Fourcade, Pierre wrote:

Regarding the issue: “Randomly”, with our custom USB device, libusb reports a systematic failure when attempting to set the device to a specific alternate setting. When setting the log levels to debug, the following issue is reported: “libusb: error [winusbx_set_interface_altsetting] SetCurrentAlternateSetting failed: Insufficient system resources exist to complete the requested service.” I have looked into existing topics regarding this issue but found none answered, at least related to USB. Usually, the issue appears to be more observable on computers that are not often turned off, but we have had the issue at least once on every computer using Windows.

What are the endpoints are in your alternate settings?  Usually, this error means that your alternate setting contains an isochronous or interrupt endpoint, and the reservation you asked for exceeded the reservation limit for the bus.  For example, if you try to start two video cameras on a USB 2 bus that's already running USB audio, that will exceed the limit.

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Tim Roberts, ti...@pr...<mailto:ti...@pr...>
Providenza & Boekelheide, Inc.