Installation guide

PicoScope 4000 Series (A API) Programmer's Guide 7

3.5

Downsampling

The driver can optionally apply a data reduction, or downsampling, process before

returning data to the application. Downsampling is done by firmware on the device

and is generally faster than using the PC's own processor(s). You instruct the driver to

downsample by passing a downSampleRatioMode argument to one of the data-

retrieval functions such as ps4000aGetValues. You must also pass in an argument

called downSampleRatio: how many raw samples are to be combined into each

processed sample.

You can optionally retrieve data using more than one downsampling mode with a

single call to ps4000aGetValues. Set up a buffer for each downsampling mode by

calling ps4000aSetDataBuffer. Then, when calling ps4000aGetValues, set

downSampleRatioMode to the bitwise OR of the required downsampling modes.

The available downsampling modes are:

PS4000A_RATIO_MODE_NONE (0)

No downsampling is performed. The downSampleRatio parameter is ignored.

PS4000A_RATIO_MODE_AGGREGATE (1)

The aggregate method generates two buffers of data for every channel, one

containing the minimum sample value for every block of downSampleRatio raw

samples, and the other containing the maximum value.

PS4000A_RATIO_MODE_DECIMATE (2)

The decimate method returns the first sample in every block of downSampleRatio

successive samples and discards all the other samples.

PS4000A_RATIO_MODE_AVERAGE (4)

The average method returns the sum of all the samples in each block of

downSampleRatio samples, divided by the size of the block.

PS4000A_RATIO_MODE_DISTRIBUTION (8)

This mode is not implemented.