> http://code.google.com/p/picusb/wiki/libusb_and_udev
The point is, that running it as root i discard the usual questions,
"do you have the correct permissions?"
Yes, i have, and tripple checked
>> Now i am not sure if this fails
>> - because of an error on pyusb
>> - because the control message is badly built and the device does'nt
>> answer (i read something about a timeout function)
>
> This is also possible. How do you know your control message
> is correct?
well, i dont.
as said, Texas Instruments doesnt provide the documentation on how to
comunicate with the device with its firmware, but there is a datasheet
detailing the internal registers which i have to edit to accomplish
things, like set DTR and RTS.
And there is also a GPL'd driver in the kernel made by them, so i am
extracting information out of it as i can.
The message structure used in the kernel for a write operation is
struct ti_write_data_bytes {
__u8 bAddrType;
__u8 bDataType;
__u8 bDataCounter;
__be16 wBaseAddrHi;
__be16 wBaseAddrLo;
__u8 bData[0];
} __attribute__((packed));
which is loaded with constants depending on the task, and passed as
the data argument (many 8bits) on an usb_control_msg(). I convert that
to the pyusb equivalent as i understand it works.
In pyusb, the data argument is the list of integers (carefuly made to
be 8bits each)
ALSO
This test is a WRITE operation.
Should it fail if the device doesnt answer/discard the message?
At this point i cant know if the usb transaction was received AND
discarded, or not received at all.
In any of both cases the error should be "Input/Output error", but
"Timeout exceed: Target doesnt answer" or "Message discarded by
device"
>> - because it is not possible to communicate with a device which has a
>> real driver assigned to it
> If there is a kernel driver bound to the device, you have to detach
> the kernel driver first. Even if you run as root, you will get problems
> if the kernel driver is in the way.
There is a driver in the kernel for sure.
Could you please expand your answer on this?
How do i detach a driver from the kernel in user space?
Also the problem would be, that it is the driver the one that loads
the firmware and initialices it.
I have had experiences where an HID device can receive usb
transactions from a normal application.
Thanks.
Diego
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