global ser;
global sample_period;

if (isempty(instrfind) ~= 1)
        o = instrfind;
        ser = o(1);
        delete(ser);
        %fclose(instrfind);
        %freeserial(instrfind);
end
ser=serial('COM7', 'BaudRate', 115200);
fopen(ser);

srate = 1/sample_period;
fprintf(ser, 'START:%d\n',srate);