API Functions | Signal Hound
bbStatus bbFetchRaw(int device, float *buffer, int *triggers);
Parameters
device Handle of a streaming device.
buffer A pointer to a 32-bit floating point buffer. The contents of this buffer
will be updated with interleaved I/Q digital samples when streaming I/Q
or IF values ranging from -1/+1 full scale when streaming IF.
triggers triggers is a pointer to an array of 68 integers representing external
trigger information relative to the buffer. Read the description below
for in-depth discussion.
Description
Retrieve the next array of I/Q samples in the stream. The length of the buffer provided to this function is
the return length from bbQueryStreamInfo() * 2. bbQueryStreamInfo() returns the length as I/Q
sample pairs. This function will need to be called ~73 times per second for any given decimation rate for
the internal circular buffers not to fall behind. We recommend polling this function from a separate
thread and not performing any other tasks on the polling thread to ensure the thread does not fall
behind.
The buffer will be populated with alternating I/Q sample pairs scaled to mV. The time difference
between each sample can be determined from the sample rate of the configured device.
The triggers parameter can be null if you are not interested in trigger position, otherwise triggers should
point to an array of 64 32-bit integers. Starting at triggers[0], positive values will indicate positions
within the returned buffer array where an external trigger occurred. The positions are zero based,
meaning the positions will be between 0 and bufferLen - 1. (Note: the minimum trigger position
detected is approximately 90) If no triggers occurred during the acquisition of the raw data, all values
will be 0. If for example, 3 external triggers occurred during the acquisition, the first three values of the
triggers array will be non-negative, and the remaining equal to 0. A returned trigger array might look like
this.
triggerArray[64] = [917, 46440, 196264, 0, 0, …, 0];
This array indicates three external triggers were detected at buffer[917], buffer[46440], and
buffer[196264]. They will always be in increasing order.
Note: Trigger positions are relative to I/Q pairs, so a trigger position at 900 would refer to the I/Q pair at
buffer[900*2] and buffer[900*2 + 1].
Note: The ports on a broadband device need to be configured to receive external triggers to take
advantage of the trigger array.
See Appendix: Code Examples: I/Q Streaming Example.
Return Values
bbNoError The device successfully began streaming.
bbDeviceNotOpenErr device is not a handle to an open device.
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