A method of boundary auto-calibration for proportional poppet valve pressure control comprises implementing an estimator to estimate a boundary deviation of the valve. A pressure command signal is detected and its derivative over time is obtained. Then, determining which closing boundary should be updated is decided based on the sign of the pressure command derivative. A pressure error is obtained by subtracting an actual wheel brake pressure from its pressure command. Then a modified pressure error is calculated and implemented in the estimation. Finally, a boundary table is updated using the resultant boundary deviation estimate. An alternate embodiment implementing a fast boundary auto-calibration scheme includes a quasi-closed-loop pressure control system. The auto-calibration test is preferably set up so that the test only needs one cycle of pressure upward sweep and pressure downward sweep in order to cover the entire operating range of pressures for the valves.