On 8/28/2016 5:13 AM, Joe wrote:
Am 28.08.2016 um 00:45 schrieb Terry Reedy:
On 8/27/2016 3:35 PM, Joe wrote:
Hi,
I'm using Python 3.5.1 with PyUSB 1.0 under Win 10 (64). We try to read
the USB output of a DMM 'UT61B'.
import usb.core
import usb.util
import usb.backend.libusb1
def Gosub():
dev = usb.core.find(idVendor=0x1a86, idProduct=0xe008) # Digital
Multimeter UT61B
if dev == None:
print ('Multimeter not found')
else:
print ('Multimeter was found')
dev.set_configuration()
cfg = dev.get_active_configuration()
intf = cfg[(0,0)]
ep = usb.util.find_descriptor(
intf,
custom_match = \
lambda e: \
usb.util.endpoint_direction(e.bEndpointAddress) == \
usb.util.ENDPOINT_IN)
if ep == None:
print ('ep is None')
else:
s = ep.read(64, 500)
print ('Len s: ' + len(s))
print ('Starting')
Gosub()
print ('Ready.-')
Result:
I presume you saw
Starting
Multimeter was found
File "d:\work-d\PythonProgs\ut61b.py", line 27, in <module>
Gosub()
File "d:\work-d\PythonProgs\ut61b.py", line 23, in Gosub
s = ep.read(64, 500)
File "D:\Python3\Lib\site-packages\usb\core.py", line 402, in read
return self.device.read(self, size_or_buffer, timeout)
File "D:\Python3\Lib\site-packages\usb\core.py", line 988, in read
self.__get_timeout(timeout))
File "D:\Python3\Lib\site-packages\usb\backend\libusb1.py", line 851, in
intr_read
timeout)
File "D:\Python3\Lib\site-packages\usb\backend\libusb1.py", line 936, in
__read
_check(retval)
File "D:\Python3\Lib\site-packages\usb\backend\libusb1.py", line 595, in
_check
raise USBError(_strerror(ret), ret, _libusb_errno[ret])
usb.core.USBError: [Errno 10060] Operation timed out
What's wrong? How to fix?
Read (again?) the doc for the interface for the device. Because reading
timed out, I suspect that it is waiting for a command for it to send
something.
Yes, I saw this:
Starting
Multimeter was found
The UT61B has two interfaces, a RS232C interface and this usb interface.
The RS232 interface works well with PySerial. It continously transmits 2
.. 3 Pakets per second with 14 Bytes each. This happens unsolicited
without any command as long as the RS232C/USB button on the DMM is active.
So I assumed the USB interface also doesn't need any command and also
transmit this stream of 2 to 3 Pakets per second. But unfortunately I
don't have any doc for the USB interface for this device.
To the accompanying software of the UT61B there is a ready windos app
which shows and logs the output of the UT61B. This app can be switched
between RS232C and USB; both work.
I asked the manufacturer (Uni-T in Shenzen) for additional info and are
now waiting for an answer.
Assumed the USB interface sends this 2 to 3 pakets per second
unsolicited - should the code shown work? Is this ok:
lambda e: \
usb.util.endpoint_direction(e.bEndpointAddress) == \
usb.util.ENDPOINT_IN)
I am in doubt: Is usb.util.ENDPOINT_IN really correct?
I do not know as I have not used the usb package.
--
Terry Jan Reedy
--
https://mail.python.org/mailman/listinfo/python-list
