Hi @kwible and welcome to the forum. The JLS file format is an open format, but it was specifically designed for Joulescope. You can find information on the underlying TLV format on datafile.py. The actual JLS fields and collection structure is not that well documented and will be expanding (but will remain backwards compatible). You can see the source code in data_recorder.py. As far as I know, joulescope.exe is the only viewer. The JLS file format will be growing in the near future to support downsampled data and GPO data.
Excel only supports a maximum of 1048576 rows (2 ^ 20), or about 1/2 second of Joulescope data. Do you want to import full-rate 2 million sample-per-second data into Excel? If so, you can use the command-line recording command to convert JLS files into either CSV (for import into Excel) or NPY format. Here is an example:
python -m joulescope recording out.jls --export out.csv
You will need to install python and then “pip install joulescope” first. For additional, help, type:
> python -m joulescope recording --help
which currently displays
usage: __main__.py recording [-h] [--plot] [--export EXPORT] [--start START]
[--stop STOP]
filename
positional arguments:
filename The capture duration in seconds.
optional arguments:
-h, --help show this help message and exit
--plot Plot the captured data (data reduction preview only).
--export EXPORT Filename for export data. ".csv" and ".npy" supported.
--start START Starting sample index. Use 0 by default
--stop STOP Stopping sample index. Use last available by default
In the not too distant future, the UI will be extended to support export to other file formats, but only JLS is currently supported.
If you just want to capture highly downsampled 2 Hz data, you can use the downsample_logging.py example. You can find more info in this post: Joulescope data logging - #2 by mliberty
Does this get you what you need? Do you have any additional questions or feedback?