AM3358: ADC control from PRU

Part Number: AM3358

Hi friends. Im trying to use the BBB built-in ADC to read values with regular sampling frequency. I am using almost all defined by Rafael Vega's github project page  (https://github.com/rvega/bbb-pru/blob/master/apps/adc/pru.c). I already made changes to read the ADC sampled values on the ARM program and everithing are working fine. BUT i have 2 questions about this program:

1) I want to know how he knows the necessaries BBB registers to configurate the ADC and the communication pipe between ADC and PRUs on this setup? I already looked the PRUSS and SITARA doccumentation but with no match the registers names used by him.

2) how i can calculate the sampling frequency? I found on his page that it was configured to 50 ksps but, trying to calculate this sampling frequency on the gived formula:

I didn't get an integer fs value, for example, using their specified values (clock_divider = 4;  open_delay = 4;  average = 1; sample_delay = 4; and channel = 6) i get 22727.2727273 Hz.. Am i missing something? 

Thanks for all..