Re: channel question for programming Olimex EEG-SMT

Stefan Jung <[email protected]>
Newsgroups gmane.comp.science.openeeg.general
Message-ID <CAC3TAzOy4Yk2E10KHDXM-E9x=XYmQWbZfxeS2p030_STzdfZDQ@mail.gmail.com>
Arnold & Daniel

Olimex did a good job with the repackaging of modEEG to SMT, but I am
pritty sure they didn't change any software.

The ADC inputs of the micro that where used for channel 3, 4, 5 & 6 in
modEEG are simply left floating on SMT-EEG (check the circuit), so you are
obviously reading stray fields that are capacitively coupled or more
likely, some sort of internal (to the micro) leakage currents from ESD
diodes or whatever.  Those leakages are random depending on temperature,
age, production batch and even cosmic radiation.  You will not find common
behaviour across SMT-EEG units.

Just ignore any and all data from channel 3 and further.  If it bugs you,
you need to short those floating inputs to GND, or disable in software.

Regards
Stefan

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