How to read am335x adc value 1000 times in 1 seconds?(let me know the s/w example )

Hi, im making a program which can read adc value 1000 times in 1 seconds.

actually, i read http://processors.wiki.ti.com/index.php/AM335x_ADC_Driver%27s_Guide.

after i read, i decide to use "one shot mode"

but it has big problem

when i made a program, it can read adc value every 1.2msec.

my source is following sentences.

int fd;

int ret;

char data[10];

while(1)

{

   usleep(500);

    fd=open("/sys/bus/iio/devices/iio:device0/in_voltage5_raw", O_RDONLY);

    ret=read(fd, date, sizeof(data));

    usleep(500);

    close(fd);

}

whenever i read adc value, i use open and close funtion.

open function spends a few time. because of that, i cannot keep the period.

i want to know another method of reading adc value in every 1msec.

actually, i tried to use continuous mode. but i cannot distinguish "chanel 5" and "exact value" like the value in one shot mode.

so i need to know exact way to read adc value.

or is it impossible to read adc value in kernel?

please help me