hysteris for move detection

src/blunderboard/boardreader.py

@@ -3,6 +3,7 @@ import RPi.GPIO as gpio
 
 
 class BoardReader:
+    hysteresis = 10
     default_gpio_mode = gpio.BCM
     default_row_gpios = [4, 5, 6, 12, 13, 16, 17, 19]
     default_column_gpios = [20, 21, 22, 23, 24, 25, 26, 27]
@@ -10,16 +11,18 @@ class BoardReader:
     def __init__(
         self,
         move_generator: MoveGenerator,
-        rows: list[int] = default_row_gpios,
-        columns: list[int] = default_column_gpios,
+        row_gpios: list[int] = default_row_gpios,
+        column_gpios: list[int] = default_column_gpios,
         gpio_mode=default_gpio_mode,
     ):
         gpio.setmode(gpio_mode)
-        gpio.setup(columns, gpio.IN, pull_up_down=gpio.PUD_DOWN)
-        gpio.setup(rows, gpio.OUT, initial=gpio.LOW)
-        self.columns = columns
-        self.rows = rows
-        self.board = self._empty_board()
+        gpio.setup(column_gpios, gpio.IN, pull_up_down=gpio.PUD_DOWN)
+        gpio.setup(row_gpios, gpio.OUT, initial=gpio.LOW)
+        self.column_gpios = column_gpios
+        self.row_gpios = row_gpios
+        self.board_history: list[list[list[str]]] = []
+        for _ in range(self.hysteresis):
+            self.board_history.append(self._empty_board())
         self.move_generator = move_generator
 
     def __del__(self):
@@ -50,30 +53,46 @@ class BoardReader:
         return True
 
     def scan(self) -> None:
-        board = self._initial_board()
-        for i, row_gpio in enumerate(self.rows):
+        next_board = self._empty_board()
+        for i, row_gpio in enumerate(self.row_gpios):
             gpio.output(row_gpio, gpio.HIGH)
-            for j, column_gpio in enumerate(self.columns):
+            for j, column_gpio in enumerate(self.column_gpios):
                 if gpio.input(column_gpio):
-                    board[i][j] = "x"
-                else:
-                    board[i][j] = " "
+                    next_board[i][j] = "x"
             gpio.output(row_gpio, gpio.LOW)
+        prev_board = self.board_history[-1]
+        self.board_history = [next_board] + self.board_history[:-1]
 
-        if not self._is_initial_board(self.board) and self._is_initial_board(board):
-            self.move_generator.reset()
-            self.board = board
-            return
+        # if the oldest board is not in inital position but all newer boards are, reset
+        # game state
+        if not self._is_initial_board(prev_board):
+            for board in self.board_history:
+                if not self._is_initial_board(board):
+                    break
+            else:
+                self.move_generator.reset()
+                return
 
-        for i, row in enumerate(board):
+        for i, row in enumerate(prev_board):
             for j, field in enumerate(row):
-                if field == " " and self.board[i][j] == "x":
-                    self.move_generator.take(i, j)
-        for i, row in enumerate(board):
+                # if the oldest board has a piece but no newer boards have it, the
+                # piece was removed
+                if field == "x":
+                    for board in self.board_history:
+                        if board[i][j] == "x":
+                            break
+                    else:
+                        self.move_generator.take(i, j)
+        for i, row in enumerate(prev_board):
             for j, field in enumerate(row):
-                if field == "x" and self.board[i][j] == " ":
-                    self.move_generator.put(i, j)
-        self.board = board
+                # if the oldest board doesn't have a piece but all newer boards have
+                # it, the piece was placed
+                if field == " ":
+                    for board in self.board_history:
+                        if board[i][j] == " ":
+                            break
+                    else:
+                        self.move_generator.put(i, j)
 
     def _print(self, board) -> None:
         print("  a b c d e f g h")
@@ -90,4 +109,4 @@ class BoardReader:
         print("  a b c d e f g h")
 
     def print(self) -> None:
-        self._print(self.board)
+        self._print(self.board_history[0])