Warning messages when using


I’m getting the following warning messages when using the Joulescope datalogging program. I use the downsample option i.e. --downsample 120 to take readings every minute. Despite the warnings it still seems to work but I would like to understand the cause of these warning messages and how I might eliminate them? I’m running pyjoulescope 0.9.11 as advised previously when I had an issue with this program.

Thanks and regards,

RESTART: C:\Users\maris\OneDrive\Documents\Luke\OneDrive\joulescope\Joulescope data logging programs\downsample_logging.py
Starting logging - press CTRL-C to stop
Found one Joulescope
2022-12-09T16:34:39 WARNING pkt_index skip: expected 41059, received 41114
2022-12-09T16:34:40 WARNING pkt_index skip: expected 41434, received 41572
2022-12-09T16:34:40 WARNING pkt_index skip: expected 42340, received 42752

Hi @LukeM - These warnings are indicating that some USB frames containing samples were missed. With the JS110, it is normal to see these when you first start streaming. If you see these warnings later during normal operation, then your host computer is not keeping up with streaming, which is more of an issue.


The JS110 has a race condition on data streaming start between the sensor starting streaming and the host starting USB Bulk IN servicing. If the host starts Bulk IN servicing either too soon (and doesn’t check back) or too soon, then the JS110 sensor will fill the JS110 control-side buffer, causing an overflow. This is the cause of the initial streaming start drops on the JS110, which are expected.

The JS220 was designed to address this issue and cleanly start data streaming.

Thanks Matt. It seems the USB on my laptop was not keeping up with the streaming but it works fine with my desktop PC.

Some laptops aggressively manage power when on battery and throttle back USB communications. I have seen a lot of variabilities here with no single, repeatable solution. You can check out this forum post which covers the basics for Windows.