Description

Functions to control pre samples.

When pre samples are selected (pre sample ratio > 0), the trigger point is located at position (pre sample ratio * record length), dividing the record in pre samples and post samples. This way it is possible to "look back in time" since the pre samples were captured before the trigger moment.

Pre sample ratio is set as a number between 0 and 1, representing the percentage of the total record length:

0 equals a trigger point at the start of the record, 0% pre samples and 100% post samples
0.5 equals a trigger point half way the record, 50% pre samples and 50% post samples
1 equals a trigger point at the end of the record, 100% pre samples and 0% post samples

By default the pre sample ratio is: 0 (no pre samples).

The pre sample buffer is not completely filled by default. When a trigger occurs before the pre sample buffer is filled, part of the pre samples will be invalid. Use ScpGetValidPreSampleCount() before collecting the data to determine the amount of valid pre samples. To ensure the pre samples buffer will be completely filled, set the trigger hold off to TH_ALLPRESAMPLES.

Functions
double	ScpGetPreSampleRatio (LibTiePieHandle_t hDevice)
	Get the current pre sample ratio of a specified oscilloscope. More...

double	ScpSetPreSampleRatio (LibTiePieHandle_t hDevice, double dPreSampleRatio)
	Set the pre sample ratio of a specified oscilloscope. More...

Function Documentation

double ScpGetPreSampleRatio ( LibTiePieHandle_t hDevice )

Get the current pre sample ratio of a specified oscilloscope.

Parameters

[in] hDevice A device handle identifying the oscilloscope.

Returns: The currently selected pre sample ratio, a value between 0 and 1.

Status values

NOT_SUPPORTED	The indicated oscilloscope does not support pre samples with the current settings.
INVALID_HANDLE	The handle is not a valid oscilloscope handle.
OBJECT_GONE	The object indicated by the handle is no longer available.
LIBRARY_NOT_INITIALIZED	The library is not initialized, see LibInit().
SUCCESS	The function executed successfully.

See also: ScpSetPreSampleRatio

Since: 0.4.0

double ScpSetPreSampleRatio	(	LibTiePieHandle_t	hDevice,
		double	dPreSampleRatio
	)

Set the pre sample ratio of a specified oscilloscope.

Parameters

[in]	hDevice	A device handle identifying the oscilloscope.
[in]	dPreSampleRatio	The required pre sample ratio, a number between `0` and `1`.

Returns: The actually set pre sample ratio, a number between 0 and 1.

Status values

NOT_SUPPORTED	The indicated oscilloscope does not support pre samples with the current settings.
INVALID_VALUE	The requested value is invalid.
INVALID_HANDLE	The handle is not a valid oscilloscope handle.
OBJECT_GONE	The object indicated by the handle is no longer available.
LIBRARY_NOT_INITIALIZED	The library is not initialized, see LibInit().
SUCCESS	The function executed successfully.

See also: ScpGetPreSampleRatio; ScpGetValidPreSampleCount; Hold off

Since: 0.4.0