Opening the device causes brief interruption of power to DUT

[andreasmueller]

Hi

When I open the Joulescope (JS110), the power to the DUT is briefly interrupted:

import joulescope
js = joulescope.scan_require_one(config='auto')
js.open()  # <-- power is toggled here

This seems to be a regression of #11 ( same behavior), but likely not related. Version 0.9.11 works fine for me.

[mliberty1]

Thanks for reporting this issue @andreasmueller. I agree that the JS110 should not disconnect power to the DUT with these commands. I quickly inspected the code, and I see why this is happening. I have not yet identified an appropriate fix. However, you can continue using version 0.9.11, as you indicated, as long as you do not need JS220 support.

I have duplicated this behavior with my setup. I connected the JS220 Evaluation Kit 1 to the JS110's inputs. I also connected an oscilloscope across the JS110's OUT terminals (Current - to Voltage -), like this:

Using Thonny, I configured the JS220 EVK1:

evk.stop()
evk.resistance = 10
evk.power_ldo(1.0)

To duplicate the issue, you first need to connect the JS110 with something that sets the current range to "auto". I used the Joulescope UI. You can then connect again. If the oscilloscope is set to trigger on voltage drop, you will see a short time where the voltage drops, like this:

[mliberty1]

The joulecope_driver commit ec2b4a9 addresses this issue. The fix is in pyjoulescope_driver 1.3.3, which is now available. Here is how to upgrade:

python -m pip install U pyjoulescope_driver

Replace "python" with however you normally launch python, such as python3 or the full path.

I am going to close this issue, but please reopen if you still see still see the problem after updating!

[andreasmueller]

I just tested it and can confirm pyjoulescope-driver 1.3.3 solves the issue.

Thank you for the quick reaction & very quick fix!