- I have a KMDF USB driver that has setup a continuous reader. I have the USB descriptor for my device configured with an interrupt endpiont using a bInterval of 9 and is operating in high speed mode. This should translate to a polling interval of 32ms. However, it is polling at 4ms instead of 32ms. I believe this might be a limitation of windows according to this page.
http://msdn.microsoft.com/en-us/library/ff539114(v=VS.85).aspx
Is there any ways around this?
- I have two different USB devices using the same driver setup that are both running continuous readers. For some reason, the polling interval of the 2nd device is changing from the 4ms to random and varying intervals from 400us to 1ms when the 1st device is present. This only seems to happen when the host is connected to the two devices at boot time. If I boot the host with both disconnected and then connect them after booting has completed, there are no issues.
Does anyone have an explanation for this?
xxxxx@intel.com wrote:
- I have a KMDF USB driver that has setup a continuous reader. I have the USB descriptor for my device configured with an interrupt endpiont using a bInterval of 9 and is operating in high speed mode. This should translate to a polling interval of 32ms. However, it is polling at 4ms instead of 32ms. I believe this might be a limitation of windows according to this page.
http://msdn.microsoft.com/en-us/library/ff539114(v=VS.85).aspx
Is there any ways around this?
Only by changing your device to be full-speed instead of high-speed.
It’s hard for me to see how this could be a problem.
- I have two different USB devices using the same driver setup that are both running continuous readers. For some reason, the polling interval of the 2nd device is changing from the 4ms to random and varying intervals from 400us to 1ms when the 1st device is present. This only seems to happen when the host is connected to the two devices at boot time. If I boot the host with both disconnected and then connect them after booting has completed, there are no issues.
Does anyone have an explanation for this?
It is extremely difficult to come up with a rational explanation for
this. The host controller driver has no clue that the two devices are
related. It doesn’t know they share a driver. Are these two devices
with the same VID/PID? Do they have different serial numbers?
–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.