If you haven't already, I'd start by generating large log files of the scales interacting with the vendor-provided software. It's easy to do this on Linux using https://www.kernel.org/doc/Documentation/usb/usbmon.txt.
Also, you have a USB HID device, which is a shortpath used by many vendors for "driverless" operation. Unfortunately this will make direct PyUSB interface slightly obnoxious. I'd check out http://pythonic-wisdom.blogspot.com/2009/07/usb-hid-with-linux-and-python.html and continue the search from there, looking less at PyUSB and perhaps more at the source of existing Python+USB+HID projects. BR, Ian On Mon, Nov 3, 2014 at 2:34 PM, Mark McClure <markfmccl...@gmail.com> wrote: > Wander and all users, > > Thank you for getting back to me. As you can tell, all of this is foreign > to me since I'm a very novice programmer. When you say poll the USB POV, > do you mean "read" data from the device? > > Here's what I tried as I removed jelly beans from a scale over 10 seconds: > > import sys > import usb.core > import usb.util > import time > > dev = usb.core.find(idVendor = 0x0DBC, idProduct = 0x0005) > if dev is None: > raise ValueError('Device not found') > > dev.set_configuration() > > endpoint = dev[0][(0,0)][0] > > timestep = 0 > > while timestep <= 10: > data = dev.read(endpoint.bEndpointAddress, > endpoint.wMaxPacketSize) > print(data) > time.sleep(1) > timestep += 1 > > > The output was this: > > array('B', [0, 0, 87, 0, 0, 0, 0, 0]) > array('B', [0, 0, 0, 0, 0, 0, 0, 0]) > array('B', [0, 0, 98, 0, 0, 0, 0, 0]) > array('B', [0, 0, 0, 0, 0, 0, 0, 0]) > array('B', [0, 0, 98, 0, 0, 0, 0, 0]) > array('B', [0, 0, 0, 0, 0, 0, 0, 0]) > array('B', [0, 0, 98, 0, 0, 0, 0, 0]) > array('B', [0, 0, 0, 0, 0, 0, 0, 0]) > array('B', [0, 0, 98, 0, 0, 0, 0, 0]) > array('B', [0, 0, 0, 0, 0, 0, 0, 0]) > array('B', [0, 0, 96, 0, 0, 0, 0, 0]) > > But I don't have any idea what this means, except that I'm guessing that > changes in weight data were not recorded. > > Has anyone worked on a device like this? Some sample code might really > help me make sense of everything. > > On Mon, Nov 3, 2014 at 2:31 AM, Wander Lairson Costa < > wander.lair...@gmail.com> wrote: > >> 2014-11-02 1:54 GMT-02:00 Mark McClure <markfmccl...@gmail.com>: >> > Hello list: >> > >> > I have three A&D EJ-3000 scales that I want to simultaneously acquire >> data >> > from every 1 minute over 24-hr periods. All scales have a USB >> interface. >> > I've started working through the pyusb tutorial, but before I confuse >> myself >> > any further, I thought I'd ask if what I want to do is even possible? >> Tech >> > support at A&D told me that retrieving weight data from the scales >> > automatically (i.e. without pushing the print button on the scales) >> could >> > not be done with USB because the interface was uni-directional. >> Instead, >> > they suggested that I switch to RS-232. Is this true, and if so why? >> > >> >> Hi, >> >> It really depends on how the firmware behaves, from USB POV, you can >> always poll the device for data each minute. But might be other >> constraints that I am not aware of. >> >> > I printed the configuration of the scale after installing pyusb and >> starting >> > the tutorial. >> > >> > >> > CONFIGURATION 1: 20 mA =================================== >> > bLength : 0x9 (9 bytes) >> > bDescriptorType : 0x2 Configuration >> > wTotalLength : 0x2d (45 bytes) >> > bNumInterfaces : 0x1 >> > bConfigurationValue : 0x1 >> > iConfiguration : 0x0 >> > bmAttributes : 0x80 Bus Powered >> > bMaxPower : 0xa (20 mA) >> > INTERFACE 0: Human Interface Device ==================== >> > bLength : 0x9 (9 bytes) >> > bDescriptorType : 0x4 Interface >> > bInterfaceNumber : 0x0 >> > bAlternateSetting : 0x0 >> > bNumEndpoints : 0x2 >> > bInterfaceClass : 0x3 Human Interface Device >> > bInterfaceSubClass : 0x0 >> > bInterfaceProtocol : 0x1 >> > iInterface : 0x0 >> > ENDPOINT 0x81: Interrupt IN ========================== >> > bLength : 0x7 (7 bytes) >> > bDescriptorType : 0x5 Endpoint >> > bEndpointAddress : 0x81 IN >> > bmAttributes : 0x3 Interrupt >> > wMaxPacketSize : 0x40 (64 bytes) >> > bInterval : 0x4 >> > ENDPOINT 0x2: Interrupt OUT ========================== >> > bLength : 0x7 (7 bytes) >> > bDescriptorType : 0x5 Endpoint >> > bEndpointAddress : 0x2 OUT >> > bmAttributes : 0x3 Interrupt >> > wMaxPacketSize : 0x40 (64 bytes) >> > bInterval : 0x4 >> > >> > Any guidance would be greatly appreciated. >> > >> >> >> -- >> Best Regards, >> Wander Lairson Costa >> >> >> ------------------------------------------------------------------------------ >> _______________________________________________ >> pyusb-users mailing list >> pyusb-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/pyusb-users >> > > > > ------------------------------------------------------------------------------ > > _______________________________________________ > pyusb-users mailing list > pyusb-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/pyusb-users > >
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