[nextBufferAddress, underflow, overflow] = Datapixx(‘WriteDacBuffer’, bufferData [, bufferAddress=0] [, channelList=[0:numChannels-1]]);
Download DAC data from local host to a Datapixx internal waveform buffer.
-“bufferData” is a 2D matrix of DAC waveform voltages. Each row of the matrix
contains the sample data for one DAC channel. Each column of the matrix contains
one sample for each DAC channel.
-“bufferAddress” is the byte address in Datapixx RAM where the buffer should
start. Specifying a bufferAddress of -1 will cause bufferData to be streamed to
the end of the buffer which was last defined in SetDacSchedule, and initialized
by a call to WriteDacBuffer with bufferAddress not set to -1.
-“nextBufferAddress” is the next Datapixx address after bufferData has been
downloaded. Multiple contiguous waveforms can be downloaded by passing the
returned nextBufferAddress of one waveform as the bufferAddress of the next
waveform. The Datapixx typically has 128 MB of internal RAM which is shared
between all I/O subsystems (DAC/ADC/AUDIO, etc). Datapixx(‘GetRamSize’) can be
used to query the quantity of RAM in your system.
-“channelList” is an optional list of the DAC channels which will be targeted by
the waveform buffer. channelList is only used for looking up the DAC voltage
ranges in order to convert double precision bufferData into binary DAC data.
channelList defaults to [0:numChannels-1], where numChannels is the number of
rows in bufferData.
-“underflow” or “overflow” are set to 1 if streaming calls to WriteDacBuffer
supply insufficient, or too much, data. If bufferAddress is passed a value of
-1, then WriteDacBuffer is streaming continuous waveform data into a circular
buffer. Streaming playback must ensure that the provided data always remains
ahead of the playback position, without providing more data than can fit in the
playback buffer. The freeBufferFrames field returned by GetDacStatus indicates
the maximum number of frames which can be written by WriteDacBuffer. If more
than this number of frames is written, an overflow occurs and there will be a
glitch in the generated waveform. If the streaming data is not supplied quickly
enough, then old data will be played, also causing a glitch. In addition to
returning underflow/overflow flags, these errors will increment the
numStreamUnderflows/numStreamOverflows fields returned by GetDacStatus.
See DatapixxDac*Demo files for examples.
###See also: SetDacSchedule