Re: [pyusb-users] question regarding HID with PYUSB on raspberry pi

[Chhavi G. <cg...@gm...>]

Thank you Jared. I will look at your project and try HIDAPI for my project.

On Thu, Jan 21, 2016 at 4:42 PM, Jared Contrascere <
jar...@li...> wrote:

> Hi, Chhavi!
>
> I'll defer to other opinions on the matter, but I think pyusb might be too
> low-level for your purposes, Chhavi. I've been able to interface with a HID
> scale on a Raspberry Pi using the python 'hidapi' package. See
> https://github.com/libretees/silverscale for an example project.
>
> --contracode
>
>
> On Thu, Jan 21, 2016 at 3:17 PM, Chhavi Goenka <cg...@gm...> wrote:
>
>> Hi,
>> I am trying to interface raspberry pi with a custom HID device via USB. I
>> am using PYUSB for this. But once I run my program i get a timeout error.
>>
>> Here is my program:
>>
>> import os
>> import sys
>> import time
>>
>>
>> import usb.core
>> import usb.util
>>
>> packet_len = 64
>>
>> # packet request function
>> def pack_request(*arguments):
>>     packet = [0x0] * packet_len
>>     i = 0
>>     for arg in arguments:
>>         packet[i] = arg
>>         i+=1
>>     return ''.join([chr(c) for c in packet])
>>
>> def show_result(bytes):
>>     sys.stdout.write("Result:")
>>     sys.stdout.write(''.join(['%d ' % abyte for abyte in bytes]))
>>
>>
>> def main():
>>     dev = usb.core.find(idVendor = 0x04d8, idProduct = 0xf2a6)
>>
>>     if dev is None:
>>         raise ValueError('Device not found')
>>
>>     #dev.set_configuration()
>>
>>     if dev.is_kernel_driver_active(0):
>>         reattach = True
>>         dev.detach_kernel_driver(0)
>>
>>     cfg = dev.get_active_configuration()
>>     intf = cfg[(0,0)]
>>
>>     ep =  usb.util.find_descriptor(
>>         intf,
>>         # match the first OUT endpoint
>>         custom_match = \
>>         lambda e: \
>>             usb.util.endpoint_direction(e.bEndpointAddress) == \
>>             usb.util.ENDPOINT_OUT)
>>
>>     assert ep is not None
>>
>>     raw = pack_request(0x00, 0x81)
>>
>>     dev.write(1, raw, 100)
>>
>>     bytes = dev.read(0x81,packet_len, 10000)
>>     show_result(bytes)
>>
>>     #print(bytes)
>>
>> if __name__ == '__main__':
>>     main()
>>
>>
>> and Here is the error:
>>
>> pi@raspberrypi:~/Documents $ sudo python multispec_usbcode_jan21.py
>> Traceback (most recent call last):
>>   File "multispec_usbcode_jan21.py", line 66, in <module>
>>     main()
>>   File "multispec_usbcode_jan21.py", line 58, in main
>>     dev.write(1, raw,100)
>>   File "/usr/local/lib/python2.7/dist-packages/usb/core.py", line 878,
>> in write
>>     self.__get_timeout(timeout)
>>   File "/usr/local/lib/python2.7/dist-packages/usb/backend/libusb1.py",
>> line 778, in intr_write
>>     timeout)
>>   File "/usr/local/lib/python2.7/dist-packages/usb/backend/libusb1.py",
>> line 856, in __write
>>     _check(retval)
>>   File "/usr/local/lib/python2.7/dist-packages/usb/backend/libusb1.py",
>> line 552, in _check
>>     raise USBError(_strerror(ret), ret, _libusb_errno[ret])
>> usb.core.USBError: [Errno 110] Operation timed out
>>
>> Please let me know how to get around this?
>>
>> Thanks,
>> Chhavi
>>
>>
>>
>>
>> ------------------------------------------------------------------------------
>> Site24x7 APM Insight: Get Deep Visibility into Application Performance
>> APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month
>> Monitor end-to-end web transactions and take corrective actions now
>> Troubleshoot faster and improve end-user experience. Signup Now!
>> http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140
>> _______________________________________________
>> pyusb-users mailing list
>> pyu...@li...
>> https://lists.sourceforge.net/lists/listinfo/pyusb-users
>>
>>
>
>
> ------------------------------------------------------------------------------
> Site24x7 APM Insight: Get Deep Visibility into Application Performance
> APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month
> Monitor end-to-end web transactions and take corrective actions now
> Troubleshoot faster and improve end-user experience. Signup Now!
> http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140
> _______________________________________________
> pyusb-users mailing list
> pyu...@li...
> https://lists.sourceforge.net/lists/listinfo/pyusb-users
>
>