channels and electrodes in eeg-smt

Started by research, January 27, 2016, 10:33:08 am

Previous topic - Next topic


January 27, 2016, 10:33:08 am Last Edit: January 30, 2016, 07:58:31 pm by research
Well, newbies like me are here to learn  :D
So, I'll answer my questions here, for others to save time:

When looking at the board docs for EEG-SMT it is clear:
CH1+ and CH1- electrode data are combined as well as the readings from CH2+ and CH2-.

The difference between CH1+ and CH1- is contained in data[0]
and the difference between CH2+ and CH2- data[1].

data[2] to data[5] contain some faint mirror image of data[1].

I also verified this by measuring, i.e. connect all five electrode according to the docs
and look at simple line plots of the raw data and the above will be obvious.

Quite a bit of the above is mentioned in some forum posts.
I added the connection to the firmware resp. modeeg-source code.

For clarification, here the snippet from the comment in main.c (firmware v2)

struct modeeg_packet
   uint8_t      sync0;      // = 0xa5
   uint8_t      sync1;      // = 0x5a
   uint8_t      version;   // = 2
   uint8_t      count;      // packet counter. Increases by 1 each packet.
   uint16_t   data[6];   // 10-bit sample (= 0 - 1023) in big endian (Motorola) format.
   uint8_t      switches;   // State of PD5 to PD2, in bits 3 to 0.

Many thanks for the hardware!