Transpose bug with analog channels

[AKuederle]

I think there is a little bug when reading the analog channels.
Here you use:

raw = np.fromstring(self._handle.read(n * analog_bytes),  dtype=analog_dtype, count=n).reshape((self.analog_used, -1))

This will result in the analog channels being in the wrong order, because you reshape the wrong way around.

Let me show you what I mean with a little example:

Let's say we have 20 analog channels, which are sampled at 5 times the frequency of the other points.
Than the information for 1 frame would look like that:

np.array(list(range(20))*5)

>>> array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16,
       17, 18, 19,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13,
       14, 15, 16, 17, 18, 19,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10,
       11, 12, 13, 14, 15, 16, 17, 18, 19,  0,  1,  2,  3,  4,  5,  6,  7,
        8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,  0,  1,  2,  3,  4,
        5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19])

Now we want to extract the 5 values belonging to each channel:

With the current implementation, that happens:

np.array(list(range(20))*5).reshape((20,-1))

>>> array([[ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14],
       [15, 16, 17, 18, 19],
       [ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14],
       [15, 16, 17, 18, 19],
       [ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14],
       [15, 16, 17, 18, 19],
       [ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14],
       [15, 16, 17, 18, 19],
       [ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14],
       [15, 16, 17, 18, 19]])

But what we actually want is:

np.array(list(range(20))*5).reshape((-1,20)).T

>>>array([[ 0,  0,  0,  0,  0],
       [ 1,  1,  1,  1,  1],
       [ 2,  2,  2,  2,  2],
       [ 3,  3,  3,  3,  3],
       [ 4,  4,  4,  4,  4],
       [ 5,  5,  5,  5,  5],
       [ 6,  6,  6,  6,  6],
       [ 7,  7,  7,  7,  7],
       [ 8,  8,  8,  8,  8],
       [ 9,  9,  9,  9,  9],
       [10, 10, 10, 10, 10],
       [11, 11, 11, 11, 11],
       [12, 12, 12, 12, 12],
       [13, 13, 13, 13, 13],
       [14, 14, 14, 14, 14],
       [15, 15, 15, 15, 15],
       [16, 16, 16, 16, 16],
       [17, 17, 17, 17, 17],
       [18, 18, 18, 18, 18],
       [19, 19, 19, 19, 19]])

Correct me, if I am mistaken, but i think that a little bug in the module. If you agree I will prepare a tiny pull request to fix it :)

Best regards

[lmjohns3]

Awesome, yes, please send a PR -- I think someone else recently filed a bug on this issue. Thanks for the detective work!

[lmjohns3]

I'll go ahead and close this, please reopen if the PR doesn't fix the problem.