Hi people.
I am on the middle of an electronic project which handles USB throught
the device TUSB3410 which is a USB to serial converter.
The main problem of this device is the intense lack of documentation
and examples of how to program it.
Any way, researching a lot i found that the BSD project has made a
firmware for it called UTICOM, but this firmware doesnt support the
standard CDC protocol, and it implements its own, with its own driver.
The device works perfectly under linux, the driver is correctly setup
and the closed-source firmware of Texas Instruments is loaded, and the
virtual serial port correctly configured and functional.
But what i need from this device is to be able to use it through a
userspace software with USB. This is not yet the problem, because i
could in last instance, use the virtual serial port, but it requires
special permissions.
Any way, this device also haves the beauty of having 4 general purpose
IO (the so called GPIOs) which, no examples uses.
I started by reading the linux driver to familiarice with the control
masages used with it, and i found that some control messages seem to
edit any register on the memory which allows me to control the GPIOs
as i want.
This is where i am using PyUSB now, to see if i can control this GPIO's.
At first i only want to change what i know that works. That is change
the state of DTR and RTS by copying the code used in the driver to
pyusb.
I think i have done that, but pyusb crashes with this error:
Traceback (most recent call last):
File "./pyusb.py", line 156, in <module>
xdata_set_register(dev,UART1_MCR, MCR_DTR | MCR_RTS, 0xFF)
File "./pyusb.py", line 136, in xdata_set_register
command, value, moduleid, msg) == len(msg)
File "/usr/local/lib/python2.6/site-packages/usb/core.py", line 668,
in ctrl_transfer
self.__get_timeout(timeout)
File "/usr/local/lib/python2.6/site-packages/usb/_debug.py", line
53, in do_trace
return f(*args, **named_args)
File "/usr/local/lib/python2.6/site-packages/usb/backend/libusb10.py",
line 541, in ctrl_transfer
timeout))
File "/usr/local/lib/python2.6/site-packages/usb/backend/libusb10.py",
line 356, in _check
raise USBError(_str_error[retval.value])
usb.core.USBError: Input/output error
I am executing it with root privileges until i know for sure that is
not pyusb the problem.
This are the lines causing the crash:
msg = message(ADDRTYPE_XDATA, DATATYPE_BYTE, 1, addr, data)
print msg
requesttype = (usb.util.CTRL_TYPE_VENDOR |
usb.util.CTRL_RECIPIENT_DEVICE | usb.util.CTRL_OUT)
command = USBCTRL_WRITE_DATA
value = 0
moduleid = USBCTRL_RAM_PORT
assert dev.ctrl_transfer(requesttype, command, value, moduleid,
msg) == len(msg)
the function message() formats the data which is passed like in the kernel.
The result of this function is:
[48, 1, 1, 0, 0, 255, 164, 48, 255]
Now i am not sure if this fails
- because of an error on pyusb
- because the control message is badly built and the device doesnt
answer (i read something about a timeout function)
- because it is not possible to comunicate with a device which has a
real driver assigned to it
- any of the other 3
Does somebody have an idea??
Thanks
Diego
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