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Author Topic: channels and electrodes in eeg-smt  (Read 1864 times)

research

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channels and electrodes in eeg-smt
« on: January 27, 2016, 10:33:08 AM »
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.

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

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For clarification, here the snippet from the comment in main.c (firmware v2)
Code: [Select]
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!
« Last Edit: January 30, 2016, 07:58:31 PM by research »