Discussion:
[pyusb-users] Multimeter USB output
Hans-Georg Joepgen
2016-10-04 10:40:27 UTC
Permalink
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.
From someone who does a LOT of code to talk to DMMs, scopes, counters,
etc? Word of advice. You're done. Declare victory and move on.
You've got it working on one interface. The other is even less well
documented and requires doing deep-down stuff against libusb because
there's no actual kernel driver, and you've got a Chinese manufacturer
of a low-end device being of little to no help so now you're trying to
reverse engineer the protocol from bad code without even the help of a
packet sniffer. This is the sort of rabbit hole that weeks manage to
fall into with nothing to show for them.
If this is an exercise in learning to work with libusb then have at.
But if what you actually need from this is to talk to the meter? You're
talking to it already. Take the win and walk.
Hi, Rob,

you mentioned 'packet sniffer'. This was important. I started to try
WireShark Portable with USBPCap and continue reading documents like 'USB
in a NutShell'. Eventually succeeded in reading and decoding the data
from this DMM with the USB interface. This is done with a Delphi XE2
program, using a dll from
https://libstock.mikroe.com/projects/view/528/usb-hid-dll-for-delphi-and-perhaps-other-languages.

Still unresolved: It seems, this Delphi program does not correctly
initialize the DMM. I have to start and stop the utility from the
manufacturer of the DMM first, then I can use my Delphi program again
and again unless rebooting or pulling off/connecting the DMM.

If this is resolved I'll try to return to work on a python solution.
Got interesting example code from Niclas Pinault. Still not working -
must look why.

Regards - Joe

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