(** This module allow to communicate with a shift-register **)

(* Source :
   - http://blog.idleman.fr/raspberry-pi-20-creer-un-tableau-de-bord-connect-au-net/
   - http://www.onsemi.com/pub_link/Collateral/MC74HC595A-D.PDF
*)
open WiringPiOcaml
(** reg : (pin_value = p_v, pin_shift = p_s, pin_apply = p_a). It is
    used to contain the needed input **)
type reg = int * int * int;;

(** The first thing to do is setupPhys (). This function put in OUTPUT
    mode the outputs and return back a bool array which represent the output of registers (begining with the first LED of the first shift register) **)
let initRegister ?nb_reg:(nb_reg = 1) reg =
  let (p_v, p_s, p_a) = reg in
  pinMode p_v 1; (* mode output *)
  pinMode p_s 1;
  pinMode p_a 1;
  Array.make (8*nb_reg) false (* return back an array for all pieces *)

let write pin value = digitalWrite pin (if value then 1 else 0)

(** This function apply all modifications to the register **)
let applyReg reg leds =
  let (p_v, p_s, p_a) = reg in
  write p_a false;
  for i = (Array.length leds) - 1 downto 0 do
    write p_s false;
    write p_v leds.(i);
    write p_s true;
  done;
  write p_a true


(** Don't forget to apply it with applyReg after **)
let clearLeds leds =
  Array.iteri (fun i x -> (leds.(i) <- false)) leds
let lightLeds leds =
  Array.iteri (fun i x -> (leds.(i) <- true)) leds