On 2013-04-25 11:09 AM, Craig Bender wrote:
Tuning like this is done in the application/driver for the device.
FWIW, It's not a dropped packet (USB-R, like other things that need
guaranteed delivery, use TCP), it's a timeout issue. A timeout due to
the latency of your WAN connection.
Many USB devices are coded with strict (over even just the USB
specification default) timing requirements since they assume they'll
be on a local bus. Some devices, such as isochronous devices, require
this strict timing, but most don't.
I would venture to guess that the latency of the WAN connection is >
20ms? That seems to be the magic number of death for USB devices that
have (sometimes needlessly) strict timing requirements.
Correct.
Call the sigpad vendor and see if they have a driver that has more
relaxed or configurable timeouts for use with USB over IP. Tell them
what the latency is for working and non-working scenarios. 20ms is a
lifetime compared to the latency of a local USB bus.
Before I do that, I think there still a problem on the linux side of things.
If I do a lsusb I get a transfer type of Interrupt with a
"bMaxPacketSize0 8" and "wMaxPacketSize 0x0008 1x 8 bytes"
Am I correct in thinking that the usb packet size should be more than 8
and that may improve the performance of the signature pad?
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