Hello.
I have a USB to I2C adapter.
For a while I was using user space library to access my device.
This library is based on linux usbdevfs driver. I use bulk
transactions.
While the bandwidth of i2c transactions was not important all was fine. Now we need 
the device to work faster and I found that the increasing my I2C bus speed do not 
actually increase overall performance. The problem is frame granularity. I can make
only one bulk transaction in one frame. This I can see from analyzer.
One I2C read transaction (for example) via my device requires
BULK_OUT - 1ms
BULK_IN  - 1ms
...
And I can't force the system make a number of BULK transactions in
one frame. The windows implementation of driver for my device
has asynchronous request ( from user level ) and this let me
make BULK_IN,BULK_OUT requests posted. This cause the host controller
pack the request in one frame.
In Linux I'm going to use URB post ioctl's provided by usbdevfs driver.
Do you think this will help me?
Should I do something else to fix the problem?
Are there any reference user space code?
The device is based on AnchorChip AN2131 IC.
Thank you. Xol.


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