ADC for continuous sampling in Beaglebone black

Hi experts,
i am new to this area,
I am using amstrong 3.8.13 kernel in BBB
at first i loaded the device tree as below,

echo cape-bone-iio > /sys/devices/bone_capemgr.*/slots

then i used analog pins however i am getting the fixed values that is values are not varying continously as i vary input analog voltage

if i go to this path
/sys/devices/ocp.2/44e0d000.tscadc/tiadc/iio:device0

and then ls -al gives me

total 0
drwxr-xr-x 3 root root 0 Jan 1 03:24 .
drwxr-xr-x 4 root root 0 Jan 1 03:24 …
-r–r--r-- 1 root root 4096 Jan 1 03:27 dev
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage0_raw
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage1_raw
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage2_raw
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage3_raw
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage4_raw
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage5_raw
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage6_raw
-rw-r–r-- 1 root root 4096 Jan 1 03:27 in_voltage7_raw
-r–r--r-- 1 root root 4096 Jan 1 03:25 name
drwxr-xr-x 2 root root 0 Jan 1 03:27 power
lrwxrwxrwx 1 root root 0 Jan 1 03:27 subsystem → …/…/…/…/…/bus/iio
-rw-r–r-- 1 root root 4096 Jan 1 03:24 uevent

there is no mode directory and buffer directory in list . please help to configure ADC In continous mode.