[Openeeg-list] Re. PC EEG system

[Stefan J. <bio...@gm...>]

Joshua,

I am a bit dumb because I never quite understand what you are saying.

As to the ADS1255/1256 these work quiet OK.  If at 1st you don't succeed,
try again.  These chips have some odd SPI specs and you need to use an
oscilloscope, or better, a logic analyser, to check and validate all timing
signals.  I debugged my ADS1255 design with a 2-channel 50Mhz scope, which
was quiet sufficient for this.  The trick is to study the datasheet in
detail and make SURE that all min and max pulse durations are met.

At the time I did the development I could not find any sample programs (yes,
I am lazy too).  Today there is a sample program - mine :-) !  If you
followed this forum the last few weeks you will know where to look.

The only **BUG** that I found is that my ADS1255 wants to run at max
sampling rate, irrespective of what I tell it to do.  That's not the end
of the world, but it does mean that there is less digital averaging taking
place which increases the noise level slightly.

With the ADS1256 you might run at the limit if you use all 8-channels at
256SPS.  The reason for that is the long settling time that must be allowed
for after channel switching.

My effective sampling rate could be pushed to 2x 1024SPS but I did not quiet
make 2x 2048SPS.  I think with some code tweaking (reducing my USB time
overhead) I could achieve 2x 2048SPS.

Stefan