Setting the sampling frequency in the PRU

I am new to beaglebone and I want to scan an analog signal (A / D) at 2kHz, I read the signal every 250 microseconds and through some forums found in this library called libpruio, but I can not configure for this sampling rate (2kHz) Output is with the maximum frequency rate, approximately 150kHz, one reading every 7 nanoseconds. Would you like to know how to control the sampling frequency or if you have another method plus simoles for this application? Thank you