
Data Translation DT2821 series


The DT2821 series contains about 6 classes of cards that are more than
just semantic changes.  This driver currently pretends that every
card in this series is a DT2821 with 16 single ended A/D lines.
Since this is not a particularily accurate assessment, please contact
the author if you have another card in the series.  The changes
that need to made in the driver for additional cards are trivial, however,
need to be tested.  The fact that the author has not done this
shows his complete laziness.


COMEDI_RANGE parameter:

Input range is controlled both by software and board jumpers.  The
jumpers select whether the input range is unipolar or bipolar, and
software selects the gain.  Check with your DT manual for how to
change jumpers.

range #		unipolar range		bipolar range
  0		   0 - +10		  -10 - +10
  1		   0 - +5		  -5 - +5
  2		   0 - +2.5		  -2.5 - +2.5
  3		   0 - +1.25		  -1.25 - +1.25

Output range is controlled by jumpers.


COMEDI_TRIGCLK trigvars:

Bits 8-11 are prescaler bits, and 0-7 are counter bits.  The sampling
frequency is determined by

  f= 4e6 / 2^(prescaler) / (255 - counter).

Maximum allowed frequency depends on the particular board in the series.
Someone at Data Translation was not good at math, and so for the purposes
of determining sampling rates, 2^1 = 1.  Check in sections 3.5 and A.9
of the DT manual for more information; trigvar is copied directly to
the pacer clock register.



David Schleef
<ds@stm.lbl.gov>
