Sample 250kHz signal from ARM core

Hi all.

I have been looking everywhere I can, but am unable to progress so once again I ask for your help.

I need to sample an analog 250kHz signal meaning that at a frequencey of 500kHz, I need to carry out an analog reading and dump the result in the mailbox for the RISC core to pick up.

How can I achieve this? I dont mind if it is assembly or C++ , Arduino, RTOS, or Lua, steam power or Oompa Loompas. Any solution that allows me to reach that sample rate, is what I will use.