How to append a new channel group?

[sdevikar]

TL;DR

Is it possible to create an MDF file with a single data group and multiple channel groups. mdf.append() adds a new data group (DG) on every call, regardless of the provided acq_name.

Long version

I would like to understand how to create a new MDF file with the following format:

Data Group
|_ Channel Group 1
  |_ signal 1
  |_ signal 2
  |_ ...

|_ Channel Group 2
  |_ signal A
  |_ signal B
  |_ ...

I have experimented with the following code a bit:

mdf_writer = MDF()

t = np.arange(5)
s = np.ones(5)

for i in range(2):
    sigs1 = [Signal(s*(i*10+j), t, name=f'SIG1{i}_{j}') for j in range(1, 4)]
    sigs2 = [Signal(s*(i*20+j), t, name=f'SIG2{i}_{j}') for j in range(1, 4)]

mdf_writer.append(
    sigs1,
    acq_name=f"channel_group1",
    common_timebase=True)

mdf_writer.append(
        sigs2,
        acq_name="channel_group2",
        common_timebase=True)

And it looks like a new data group is indeed created with each call of append as per the documentation. i.e. it produces a structure attached in the screenshot.

I looked into the extend API and I am confused. The description says "Extend a group with new samples.", but I guess that refers to adding to existing measurements.

I'd appreciate any help! Thanks in advance.

[danielhrisca]

Use a list of channels instead of a channel when you call append, and they will all go in a single channel group