From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-03-14 06:18:29
Hi, just providing a bit of background info for your EDF discussion
(a bit late perhaps. :-)
* Data loss: If data is transmitted at say 56700 bps, data loss will
happen. A lot.
A solution is to increase the interrupt priority of the serial port
interrupt to the highest level. This is untested, but should ensure
that no data at all is lost - i.e. you won't need CRC checking. If
that doesn't work, we will have to use USB with a large hardware fifo
(4kb) for PC's running Windows. Linux/embedded systems can be fixed
by installing a real-time kernel.
For me, data loss/sync loss is not acceptable at all so I will work
hard to overcome it.
Testing the serial port can be done by anybody who can program and
owns two computers, so volunteers are welcome. Start a new thread on
that topic if you are interested...
* Data width: The high resolution EEG will use 24-bit samples. The
lower 8.5 bits are noise (according to the ADC data sheet anyway),
but by downsampling from 48kHz to 256Hz you get increased resolution -
theoretically 3.8 bits extra, so it would be nice to allow > 16 bits
per sample in the file specification. However, 16 bits in itself is
pretty good.
* "brain-stem latencies": Would definitely need a real-time (or low
latency) kernel, so linux would be the only real option there. A
regular windows/linux setup has a worst-case latency of hundreds of
milliseconds (yuck).
Regards,
Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:40 BST