diff --git a/src/fen.c-move-to-temp-migration-bitboard__fen.c b/src/fen.c-move-to-temp-migration-bitboard__fen.c
new file mode 100644
index 0000000..86d3206
--- /dev/null
+++ b/src/fen.c-move-to-temp-migration-bitboard__fen.c
@@ -0,0 +1,175 @@
+/* fen.c - fen notation.
+ *
+ * Copyright (C) 2021 Bruno Raoult ("br")
+ * Licensed under the GNU General Public License v3.0 or later.
+ * Some rights reserved. See COPYING.
+ *
+ * You should have received a copy of the GNU General Public License along with this
+ * program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+
+#include <debug.h>
+
+#include "chessdefs.h"
+#include "position.h"
+#include "board.h"
+#include "fen.h"
+#include "piece.h"
+
+/* Starting Position :
+ * rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
+ * After 1.e4 :
+ * rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1
+ * After 1... c5 :
+ * rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR w KQkq c6 0 2
+ * After 2. Nf3:
+ * rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2
+ *
+ * 1 : White uppercase
+ * 2 : next move (w or b)
+ * 3 : Castling capabilities: "-" if none, KQ/kq if white/black can castle
+ *     on K or Q side
+ * 4 : en-passant: if pawn just moved 2 squares, indicate target square (e.g.
+ *     for e2-e4 this field is e3)
+ * 5 : half moves since last capture or pawn advance (for 50 moves rule)
+ * 6 : full moves, starts at 1, increments after black move
+ *
+ */
+
+// warning, we expect a valid fen input
+pos_t *fen2pos(pos_t *pos, char *fen)
+{
+    char *p = fen;
+    short rank, file, skip, color, bbpiece;
+    piece_t piece;
+    board_t *board = pos->board;
+#   define SKIP_BLANK(p) for(;*(p) == ' '; (p)++)
+
+    pos_clear(pos);
+    /* 1) get piece placement information
+     */
+    for (rank = 7, file = 0; *p && *p != ' '; ++p) {
+        color = isupper(*p)? WHITE: BLACK;
+        char cp = toupper(*p);
+        switch (cp) {
+            case CHAR_PAWN:
+                bbpiece = BB_PAWN;
+                piece = PAWN;
+                goto set_square;
+            case CHAR_KNIGHT:
+                bbpiece = BB_KNIGHT;
+                piece = KNIGHT;
+                goto set_square;
+            case CHAR_BISHOP:
+                bbpiece = BB_BISHOP;
+                piece = BISHOP;
+                goto set_square;
+            case CHAR_ROOK:
+                bbpiece = BB_ROOK;
+                piece = ROOK;
+                goto set_square;
+            case CHAR_QUEEN:
+                bbpiece = BB_QUEEN;
+                piece = QUEEN;
+                goto set_square;
+            case CHAR_KING:
+                bbpiece = BB_KING;
+                piece = KING;
+                //pos->bb[color][BB_KING] = BB(file, rank);
+                //goto set_square;
+            set_square:
+#               ifdef DEBUG_FEN
+                log_i(5, "f=%d r=%d *p=%c piece=%c color=%d\n",
+                      file, rank, *p, cp, color);
+#               endif
+                pos->bb[color][bbpiece] |= BB(file, rank);
+                pos->occupied[color] |= BB(file, rank);
+                SET_COLOR(piece, color);
+                board[SQ88(file, rank)].piece = piece;
+                board[SQ88(file, rank)].s_piece =
+                    piece_add(pos, piece, SQ88(file, rank));
+                file++;
+                break;
+            case '/':
+                rank--;
+                file = 0;
+                break;
+            default:
+                skip = cp - '0';
+                while (skip--) {
+                    board[SQ88(file++, rank)].piece = EMPTY;
+                }
+        }
+    }
+#   ifdef DEBUG_FEN
+    for (rank = 7; rank >= 0; --rank) {
+        for (file = 0; file < 8; ++file) {
+            log(5, "%02x ", board[SQ88(file, rank)].piece);
+        }
+        log(5, "\n");
+    }
+#   endif
+
+    /* 2) next move color
+     */
+    SKIP_BLANK(p);
+    SET_COLOR(pos->turn, *p == 'w' ? WHITE : BLACK);
+    p++;
+
+    /* 3) castle status
+     */
+    SKIP_BLANK(p);
+    pos->castle = 0;
+    if (*p != '-') {
+        for (; *p && *p != ' '; ++p) {
+            switch (*p) {
+                case 'K':
+                    pos->castle |= CASTLE_WK;
+                    break;
+                case 'k':
+                    pos->castle |= CASTLE_BK;
+                    break;
+                case 'Q':
+                    pos->castle |= CASTLE_WQ;
+                    break;
+                case 'q':
+                    pos->castle |= CASTLE_BQ;
+                    break;
+            }
+        }
+    }
+    p++;
+
+    /* 4) en passant
+     */
+    SKIP_BLANK(p);
+    pos->en_passant = 0;
+    if (*p != '-') {
+        //SET_F(pos->en_passant, C2FILE(*p++));
+        //SET_R(pos->en_passant, C2RANK(*p++));
+        pos->en_passant = SQ88(C2FILE(*p), C2RANK(*(p+1)));
+        pos += 2;
+    } else {
+        p++;
+    }
+
+    /* 5) half moves since last capture or pawn move and
+     * 6) current move number
+     */
+    SKIP_BLANK(p);
+    //log_i(5, "pos=%d\n", (int)(p-fen));
+    sscanf(p, "%hd %hd", &pos->clock_50, &pos->curmove);
+#   ifdef DEBUG_FEN
+    log_i(5, "50 rule=%d current move=%d\n", pos->clock_50, pos->curmove);
+#   endif
+    return pos;
+}