Re: [Pyusb-users] From libusbJava to pyusb

[Wander L. <wan...@gm...>]

What does this expression mean: (0x03 << 8) | var ? I could not see it
in the Python code...

Wander

2010/1/17 Henning Spille <h.s...@go...>:
> Hi there,
>
> i'm trying to use this multi-plug (http://www.nw-s.net/images/sispm.jpg) with pyusb. I already used it form libusbJava which is based on the libusb from linux.
> As it was no problem for me to get it working in java, i'm struggling with python. Well, i'm new to python (actually these are my first few lines of code) but i guessed it is more an pyusb related problem - caused by me.
>
> I hoped i could convert (manually for sure) the code from libusbJava to pyusb, but it does not work - yet. I attached some lines of code, dmesg output and lsusb --verbose info, but i don't know if it is necessary. Please can someone have a look at the controlMsg translation:
>
> Java Code:
>
> int reqtype = 0x21;
> // USB_DIR_OUT + USB_TYPE_CLASS +
> // USB_RECIP_INTERFACE /*request type*/
> int request = 0x09; // writing
> byte var = (byte) (3 * plugNumber);
> int index = 0;
> byte _on = 0x03;
> byte _off = 0x00;
> switchTo = _on;
> byte buffer[] = { var, switchTo };
> int timeout = 250;
> int size = 2;
> if (LibusbJava.usb_control_msg(handle, reqtype, request, (0x03 << 8)
>                                | var, index, buffer, size, timeout) < 0)  .....
>
> My pyUsb Translation:
>
>
> on = 0x03
> off = 0x00
> timeout = 250
> try:
>   print "Trying to switch"
>   var = (3 * plugNumber)
>   reqBuffer = [0] * 2
>   reqBuffer[0] = var
>   reqBuffer[1] = off
>   print "Bytes to write: " + str(reqBuffer)
>   written = handle.controlMsg(0x21, 0x09, reqBuffer,  value=0, index=0, timeout=250)
>   print "Bytes written: " + str(written)
> except Exception, err:
>   print >> sys.stderr, err
>   handle, device = None, None
>
>
>
> The code works, no error in dmesg or elsewhere, but nothing happends at the device - so i guess there is something wrong somewhere. Can i somehow debug the communication?
>
> Would be nice if someone has some minutes to help me,
>
> Regards,
>
> Henning
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