User-agent: Mozilla Thunderbird 0.5 (X11/20040208)
Hi all,
I'm developing a device driver for a USB communications device.
I've run into problems with latency when sending and receiving messages
to and from my USB device. The device is controlled via firmware
commands which are sent over the bulk out pipe and whose responses are
read in through the bulk in pipe.
Each firmware command takes 0.5 seconds with my driver, which is 3
orders of magnitude too slow. The corresponding Windows driver for the
same device reports firmware command turnaround times of between 500 and
1200 _micro_seconds.
I've also noticed data transfer is too slow by a factor of 20 or so.
Transfer rate should be around 20-30 MBit/sec, I'm currently getting 0.5
Mbit/sec transmit and 1.0 Mbit/sec receive. My guess is that maybe
something's working in low speed or full speed mode, instead of high
speed. However, that wouldn't explain the terrible latency I'm
experiencing. The amounts of data that I'm transmitting are so low (~20
bytes, on average), that data transfer time can't be the reason.
Any ideas?
Cheers,
Gerald
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