Well here I found a API published by Emotiv. But not sure using it in the right way yet.
“double * buffer = (double *)malloc(sizeof(double)*maxT*nChannl);
DataHandle hData = IEE_MotionDataCreate();
int ret = IEE_DataGetMultiChannels(hData, ChannelList, nChannl, &buffer, sizeof(double)*maxT);
if(ret != EDK_OK){NSLog(@”%i”,ret);}
else{}”
It returns 769 as ret from IEE_DataGetMultiChannels().