Python based arbitrary waveform generator.


Sample/Update rates:
  There will be two types of sample- or update-rates permissable.
  1.  Fixed update rates.
    An example of this would be a hardware card that updates a channel for every
    clock pulse and this clock pulse rate is fixed.  For hardware devices
    configured to operate with this type of update clock, the number of samples
    to update will automatically be calculated to the nearest clock pulse.
  2.  Arbitrary timing update rates.
    Some hardware devices may be configured to use an arbitrary timing signal as
    the update clock.  An example of this would be when a channel from a
    Viewpoint DIO-64 card is configured to be used as a clock for other devices.
    For this type of configuration, the clock rate will automatically change
    such that the minimum number of clocks are emitted to support all
    channels/devices tied to the clock.  Clock pulses will designed to allow
    all voltage transitions as specified at their transition time within the
    maximum clock resolution possible (the internal clock rate of the DIO-64 for
    example).  In other words, a single waveform element may have a variable
    clock depending on whether other waveform channels similarly clocked need to
    have transitions in the mean time.


things that will/will not cause errors:
  1.  channels without devices selected will be ignored
  2.  waveforms elements with no channel selection (i.e. empty) will be ignored