niHSDIO_FetchWaveformU8
Specific Function
C Function Prototype
ViStatus niHSDIO_FetchWaveformU8 (ViSession vi, ViInt32 samplesToRead, ViInt32 maxTimeMilliseconds, ViInt32* numberOfSamplesRead, ViUInt8[] data);
Purpose
Transfers acquired binary data from onboard memory to PC memory.
The data was acquired to onboard memory previously by calling the
niHSDIO_Initiate
function.
If the number of samples specified in samplesToRead
is still not available after the number of milliseconds specified in
maxTimeMilliseconds, this function returns no data with a timeout
error.
The fetch position can be modified by using niHSDIO_SetAttributeViInt32 and the NIHSDIO_ATTR_FETCH_RELATIVE_TO or NIHSDIO_ATTR_FETCH_OFFSET attributes. The default value for NIHSDIO_ATTR_FETCH_RELATIVE_TO is NIHSDIO_VAL_CURRENT_READ_POSITION. The default value for NIHSDIO_ATTR_FETCH_OFFSET is 0.
Calling this function is not necessary if you use the niHSDIO_ReadWaveformU8 function, as the fetch is performed as part of that function.
Parameters
| Name | Type | Description |
|---|---|---|
| vi | ViSession | This handle identifies your instrument session. vi was obtained from niHSDIO_InitAcquisitionSession. |
| samplesToRead | ViInt32 | Specifies the number of samples to fetch. |
| maxTimeMilliseconds | ViInt32 | Specifies in milliseconds how long to allow the function to
complete before returning a timeout error.
A value of 0 causes the function to return immediately with up to the number of samples specified in samplesToRead. If you set maxTimeMilliseconds to a value other than 0, and timeout occurs before all the samples are acquired, you receive a timeout error. If you specify a value for samplesToRead that is greater than the number of samples in the device memory, NI-HSDIO returns the available samples after maxTimeMilliseconds. A value of -1 causes the function to never time out. |
| numberOfSamplesRead | ViInt32 | Returns the number of samples that were successfully fetched and transferred into data[]. |
| data | ViUInt8[] | Returns the preallocated array where samples are written. |