API Stream Data. LXDeviceAPI

struct : ST_STREAMDATA_LXDAPI

LXDeviceAPI.h provides the typedef of ST_STREAMDATA_LXDAPI.

// struct for stream. LXDeviceAPI.h

typedef struct _stStreamData_LXDAPI
{
...
  unsigned int*	Event_StreamData_CS; // array for event marking

  double*	Wave_StreamData_CS;  // array for measured multi channel bio signal
...


}ST_STREAMDATA_LXDAPI;

The most important member variables are  Wave_StreamData_CS for multi channel bio signal and Event_StreamData_CS for event marking.

Usages

Declare the variable for stream data type and feed into OpenDevice as a address of variable.

ST_STREAMDATA_LXDAPI stStreamData; 
int NumSampleReturn = 32 ; //available range 1~ 128. the number of samples to get the stream data per each message from LXDeviceAPI. 
OpenDevice_LXDeviceAPI( , &stStreamData,NumSampleReturn , );

Dynamic Memory Allocation by LXDeviceAPI

LXDeviceAPI dynamic allocates the memory for arrays when you call the OpenDevice. The size of memory is determined by the OpenDevice’s parameter int numsample_return  which is the number of samples per each message  received.  LXDeviceAPI deletes the memory if CloseDevice is called.

Memory Map, Array Indexing.

The array Wave_StreamData_CS has real time measured sampling data from the device.

The number of samples is determined by a parameter  int numsample_return when you call the OpenDevice.

 

The Event_StreamData_CS has a value of “event id” which is the same as a parameter unsigned int event_id when you call the EventMarkingOnStream. The number of samples is the same as that of Wave_StreamData_CS.

Retrieving the one sample from Stream Array

Array indexing for wave data

The following code shows how to get the one sample for specific channel index and sample index,

double one_sample_wave = stStreamData.Wave_StreamData_CS[sample_index + NumSampleReturn * channel_index ]

where,

• channel_index  : Available value range form 0 to ( number of channel   – 1). The number of channel is specific to device. In the case of  QEEG-64FX, the number of channel is 67 ( EEG 64ch + Bipolar 3ch).
• sample_index : Available value range from  0 to (NumSampleReturn – 1). The NumSampleReturn is determined by the parameter int numsample_return when you call the OpenDevice.

Array indexing for event data.

unsigned int one_sample_event = stStreamData.Event_StreamData_CS[ sample_index ]

where,

• sample_index : Available value range from  0 to (NumSampleReturn- 1).The NumSampleReturn is determined by the parameter int numsample_return when you call the OpenDevice.

 

Indexing Example

Array indexing example for two channel signals and event. The chart plots the both signals and event simultaneously.