Datapixx(‘SetDoutSchedule’, scheduleOnset, scheduleRate, maxScheduleFrames [, bufferBaseAddress=8e6] [, numBufferFrames=maxScheduleFrames]);
Configure a schedule for autonomous TTL digital output waveform playback.
Digital output schedules drive bits DOUT0-DOUT15 on the “Digital OUT” db-25
connector. Digital output waveforms can be used to generate complex triggering
sequences and any other arbitrary digital waveforms.
-“scheduleOnset” is the desired delay (in double precision seconds) between
schedule initiation, and when the first waveform sample is sent to the digital
-“scheduleRate” is the rate at which successive waveform samples are sent to the
digital outputs. scheduleRate has two formats. It can be a single number, or a
2 element array. If it is a single number, then it specifies integer
samples/second. If it is a 2 element array, then the first element specifies the
rate, and the second element specifies the units of the rate.
If units = 1, then the rate is interpreted as integer samples/second.
If units = 2, then the rate is interpreted as integer samples/video frame.
If units = 3, then the rate is interpreted as double precision seconds/sample
Regardless of the actual format chosen, the resulting update rate cannot exceed
-“maxScheduleFrames” has two modes, depending on whether the full waveform has a
fixed known length. If the waveform length is known (eg: 100000 samples), then
just pass 100000 to maxScheduleFrames. In this mode, once the digital waveform
schedule is started with StartDoutSchedule, the schedule will terminate
automatically when maxScheduleFrames has been reached. If the waveform length is
not known in advance, then pass 0 to maxScheduleFrames. In this mode, the
waveform will continue until the schedule is manually stopped using
-“bufferBaseAddress” specifies the start of the RAM buffer which holds the
waveform data inside the Datapixx. Use WriteDoutBuffer to download the waveform
data to this address before calling StartDoutSchedule.
-“numBufferFrames” specifies the size of the waveform buffer in the Datapixx
RAM. For many applications, the Datapixx has enough RAM for WriteDoutBuffer to
download multiple complete waveforms before initiating playback. In these cases,
numBufferFrames could be left at its default value of maxScheduleFrames. If
maxScheduleFrames is larger than numBufferFrames (or 0), then each time the
waveform frame counter reaches a multiple of numBufferFrames, the waveform
buffer address automatically wraps back to bufferBaseAddress. This circular
buffer effect can be used for streaming arbitrarily long waveforms into a
digital output schedule. Simply monitor freeBufferFrames returned by
GetDoutStatus, and use WriteDoutBuffer in streaming mode to append new waveform
data into buffer space which has already been played. The circular buffer effect
can also be used to implement periodic waveforms very efficiently. A periodic
clock output could be generated with a buffer filled with only 2 samples; one
high and one low. The resulting clock output will run continuously.
Note that every call to StartDoutSchedule must be preceeded by a call to
SetDoutSchedule (ie: multiple calls to StartDoutSchedule each require their own
call to SetDoutSchedule)).
Note that schedule timing is implemented in hardware with microsecond precision.
See DatapixxDout*Demo files for examples.