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This calibration is for chess manipulation only. It is different from Stereo depth calibration, which is used for navigation.

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What this controls

Chess calibration is used to:
  • map chess squares (A1 to H8) to arm coordinates
  • move pieces with pick_up_piece_simple
  • move to the board observation pose for detect_opponent_move
Calibration is stored in ~/board_calibration.json.

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Board mapping used by chess skills

Current mapping is:
  • top_left = A8
  • top_right = H8
  • bottom_right = H1
  • bottom_left = A1

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Full board calibration (first setup, current beta flow)

In the current chess beta flow, calibration is driven from the two top corners only (A8, H8) using recalibrate_manual. The skill then computes A1 and H1 automatically and writes all 4 corners to ~/board_calibration.json. Use this on first setup or any time the board position changes:
  1. Put the chessboard in its final position.
  2. Run arm_utils(command="torque_off").
  3. Manually place the end effector above the center of A8.
  4. Run recalibrate_manual(corner="A8").
  5. Manually place the end effector above the center of H8.
  6. Run recalibrate_manual(corner="H8").
  7. Run arm_utils(command="torque_on").
  8. Verify ~/board_calibration.json contains top_left, top_right, bottom_left, and bottom_right.
You can still use board_calibration_agent (record_position) for a manual 4-corner workflow, but the chess agent calibration flow uses the top-corner method above.

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Quick manual recalibration for drift

Use this if board placement is the same but piece placement quality drifted.
  1. Run arm_utils(command="torque_off").
  2. Manually place the end effector above the center of A8.
  3. Run recalibrate_manual(corner="A8").
  4. Manually place the end effector above the center of H8.
  5. Run recalibrate_manual(corner="H8").
  6. Run arm_utils(command="torque_on").
recalibrate_manual recomputes all four corners and updates ~/board_calibration.json.

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Validate before playing

Run a physical validation move:
  1. Place a spare pawn on A4.
  2. Keep H5 empty.
  3. Run:
pick_up_piece_simple(square="A4", place_square="H5", piece="pawn", is_capture=False, speed=1.5)
  1. If placement is off, run manual recalibration and retest.

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Troubleshooting

  • board_calibration.json missing or invalid:
    • rerun the top-corner calibration flow (A8 then H8 with recalibrate_manual)
  • detection works but arm pose over board is wrong:
    • verify all four corners exist in ~/board_calibration.json
  • reset fails because calibration is missing:
    • complete full calibration, then run reset_chess_game(...) again