23 Aug
2007
23 Aug
'07
12:05 p.m.
USB 1.1 transfers happen at 1ms bounderies. Setting 64Frames/period period interrupts will happen within 1ms or 2ms distances.
I was not aware of the 1ms granularity for USB interrupts. Would USB 2.0 or Firewire offer a better granularity?
Technically both operate at down to 1/8ms.
Linux's USB 2.0 ehci driver doesn't go there and limits isochronous transfer granularity at 1ms. I posted a patch to linux-usb-devel, which enables 1/8ms granularity isochronous transfer. There was exactly 0 answer to it. And I was too lazy to follow up on that ;-)
Regarding Firewire: I guess the "new stack" can operate at 1/8ms granularity.
Karsten