From: Doug Sutherland (wearable_at_earthlink.net)
Date: 2001-12-04 02:27:15
I took a look at all of the schematics on the OpenEEG site
and made some notes so its easier to understand differences
between all of these designs. Joerg: you have been busy!
Thanks for sharing all of your work. Following is a summary
of each design, and I have made a few comments below that.
COMADC01 (schematic dated 07/28/2001)
- 1 channel isolated 8+ bit ADC for RS232 PC interface
- Uses no microcontroller, direct connect to PC
- Uses 555 timers for clock generation and pulse width modulation
- Uses no instrumentation amp, signals feed into PWM circuit
- Sends pulses to PC over RS232 handshake lines (RTS and CTS)
- Pulse range 1mS to 10 uS
- PC code must run in DOS only mode (disabling intterupts)
- This will not work with the DigitalGuru software
- New software required for FFT analysis etc
comEEG01 (schematic dated 09/03/2001)
- 1 channel isolated 8+ bit ADC for RS232 PC interface
- Uses no microcontroller, direct connect to PC
- Uses differential uV amplifier
- Uses INA114 instrumentation amps and OPA2604 op-amps
- Uses 7555 timer for calibration circuit
- Uses 555 timer for pulse width modulation
- Sends pulses to PC over RS232 handshake lines (RTS and CTS)
- Pulse range 1mS to 10 uS
- PC code must run in DOS only mode (disabling intterupts)
- This will not work with the DigitalGuru software
- New software required for FFT analysis etc
GamePortEEG (no date on schematic)
- Uses no microcontroller, direct connect to PC
- Uses differential uV amplifier
- Uses game port interface to PC
- I can't tell what the ICs are on the board
eeg_rs232_01_00905 (schematic dated 09/04/2000)
- 2 channel isolated EEG amp with RS232 interface
- Uses AT90S4433 microcontroller
- Microcontroller does ADC and connects to PC
- Sends data to PC over RS232 data lines (RX and TX)
- Uses differential uV amplifier
- Uses INA114 instrumentation amps and TCL232 op-amps
- Uses 7555 timer for calibration circuit
- This design is fairly well documented
- Firmware source and rom image available
- Sample data stream is available
- PC Cable connectiotion documented
- Test procedures documented
- Should work with DigitalGuru software
modEEGdigi01 (schematic dated 11/28/2001)
- 2-channel isolated EEG amp with RS232 interface
- Uses AT90S4433 microcontroller
- Microcontroller does ADC and connects to PC
- Sends data to PC over RS232 data lines (RX and TX)
- Uses 6N139 Opto couplers
- Uses differential uV amplifier
- Uses INA114 instrumentation amps and TCL277 op-amps
- Input stage modeled after Biosemi designs
- Amp on separate board, connects to ADC board w/uC
- Not much documentation included yet
- PC Cable connectiotion documented
- Firmware source and rom not in zip file
- Should work with DigitalGuru software
Here are some personal opinions/comments on these designs
- ComADC and ComEEG could be problematic:
- interrupts must be disabled for timing reasons
- must run in DOS only for above reason
- will not work with either windows or linux
- you could boot a windows machine into DOS only
mode and run the software, but cannot run any
other software at the same time.
- will not work with DigitalGuru software
- Perhaps ComADC or ComEEG could be connected to a
microcontroller to solve the above problems, but
in my opinion it's better to use the new input
stage as in ModularEEG.
- The RS232EEG and MODEEG designs look much better.
The use of uC for ADC and RX/TX data lines is a
better approach. This allows easy integration
with both traditional PCs and embedded PCs. I
could easily take these designs and add on
extra circuits for ECG, EMG, GSR, and temp if
I wanted to, I like the flexibility. These also
use a data format which (I think) will work
with the DigitalGuru software.
- There are no features in any of these designs
for standalone operation, all require a PC.
They could be modified slightly to add audio
feedback and/or interfaces to small LCDs that
can display text, bar graphs, and line graphs
of the waves. I have done a lot of work with
this and I'm willing to add these features to
the existing designs. All that is needed for
small LCD is one output pin from the uC and
one RS232 level converter (recommend DS275).
Check out my jacket sleeve display, it would
be REALLY cool to display EEG data here ...
http://home.earthlink.net/~wearable/jacket-wearable.html
My overall opinion is that the ComADC, ComEEG, and
GamePortEEG designs are too low end and are too
restricted and limited. I think we need a design
with microcontroller interface to do a good job on
the PC software side of things. People will want
to run Windows and/or Linux applications and will
expect some good graphics. We cannot make a good
GUI in DOS. People will not want to run machines
in DOS only mode, they will want to be able to
cut and paste EEG data into spreadsheets and such
without having to reboot.
I assume that the new ModularEEG replaces the old
EEG_RS232 with improvements in the input stage. I
assume then that the old EEG_RS232 is obsoleted.
I am interested in making a prototype of the new
ModularEEG design. I have a few questions for
Joerg on this new design:
1) Is there a working prototype of ModularEEG?
2) Has this PCB board design been tested?
3) Do you consider this to be a final version?
4) Can I get the firmware sources from you?
5) Can this be used with the DigitalGuru
binary source code?
6) Do you have any specs on the frequency response
band width, sampling rate, CMMR, noise, etc?
Very nice work Joerg. My vote is to work on
ModularEEG instead of ComADC for all of the
above reasons.
Question for everyone: why don't we do a low
volume order of PCB boards from ExpressPCB
for the ModularEEG design?
-- Doug
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The human-computer interface seems to be stuck on the
WIMP (windows, icons, menus, pointer) model. What I'd
like is to have you call me and my clothing answers.
http://home.earthlink.net/~wearable/jacket-wearable.html
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