I have a motion capture system that I've been using the USB Visor driver in the 2.6 kernel tree to communicate with. This works fine except that some frames are dropped (a frame is a set of position and orientation values from all the motion sensors) - data is generated at 240Hz, and every couple of frames the next one doesn't get through. I wasn't concerned about this initially, but it becomes a slight pain when analysing the data.
I've modeled a new driver based upon visor.c, however I'm unsure how I could modify the bulk transfers to improve this. The vendor supplied Windows driver doesn't drop frames, so it isn't an inherent limitation of the system.
Any suggestions on how I could figure out what is happening here and/or resolve this would be appreciated. My ultimate aim is to get every frame with minimal latency (i.e. the time when the data is captured to when it is available to the application is minimal).
Some further details:
Using kernel 2.6.1 on a Redhat 9 system.
The machine is an Athlon XP2200+ with 512MB RAM, and has an UHCI controller.
The machine has the sole purpose of receiving the motion capture data via USB and sending it over a network to another machine.
The motion capture device has an EZ-USB FX chip that handles USB communication.
Each frame consists of 640 bytes. Hence the data is generated at 153.6kb/s.
The /proc/bus/usb/devices listing for the motion capture device:
T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 3 Spd=12 MxCh= 0 D: Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 P: Vendor=0f44 ProdID=ff12 Rev= 0.01 C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr= 0mA I: If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=usbserial E: Ad=82(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms E: Ad=02(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms E: Ad=06(O) Atr=02(Bulk) MxPS= 8 Ivl=0ms
Thanks!
Regards, Daniel
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