Strange double sampling

[Andres9713]

Hi, we are having a strange issue with pyPhotometry specific to one computer (a laptop). The issue is that in 2EX_2EM_pulsed mode the GUI seems to be recording twice the number of samples as it should. For example, we set the Sampling Rate to 130Hz and record for 1 minute and the resulting .ppd file shows 15,600 samples for each of the two analog channels instead of the expected 7,800 samples. Looking at these signals it seems that every other sample is 'correct', while it is unclear what the other half are. Notably, on the GUI itself we think that the data looks normal, so it seems that this likely has something to do the way the .ppd files are being saved.

We are using pyPhotometry V1.1 and we have seen the same behavior with the V1 and V2 boards. We have tried reinstalling all the required packages in a new environment, but this new environment also behaved the same way, again, only on this computer.

Thank you for any insight into what could lead to this odd behavior.

[ThomasAkam]

Hi @Andres9713,

I have never encounted this issue before and it is not obvious to me what could be causing it. What operating system is the laptop running? It would be worthwhile checking whether the version of python and numpy are different on the laptop from other computers that are working normally, and potentially creating a python environment with exactly the same version numbers for python and the numpy to check if this fixes the issue.

The only thing I can imagine that could cause this behaviour would be if the data was somehow converted from 2 bytes per sample to 4 bytes per sample before being saved, such that you end up with two extra bytes in the data file for every sample, which then show up as extra samples interleaved between the true samples when the file is loaded. However, I don't see how this could happen, as when saving to ppd that data that is saved is exactly that which is read from the board, and the dtype is specified when it is read from the serial line. The reading of new data from the board and saving it to disk all happens in the Acqusition_board.process_data() method in case you want to take a look or print out some diagnostic infomation about dtypes.