switch(IoControlCode) case IOCTL_TOUCH_CALIBRATE_SET_COEFFS: // Lock mutex, copy coefficients into device context, apply to next touch // Store in registry via WdfRegistry break; case IOCTL_TOUCH_CALIBRATE_GET_RAW: // Temporarily bypass calibration, read raw I2C registers, return break;
WDFKEY hKey; WdfDeviceOpenRegistry(Device, PLUGPLAY_REGKEY_DEVICE, &hKey); // Read REG_BINARY "CalibCoeffs" -> store in device context WdfRegistryClose(hKey); When user-mode sends SET_COEFFS , write back immediately to the registry.
#define IOCTL_TOUCH_CALIBRATE_SET_COEFFS \ CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS) #define IOCTL_TOUCH_CALIBRATE_GET_RAW CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_ANY_ACCESS)
By following the architecture and practices outlined in this article—custom IOCTL interfaces, registry-backed coefficient storage, real-time coordinate transformation, and thorough debugging—you can build a driver that is robust, certifiable, and adaptable to any touch sensor or environmental condition.
CalibratedPoint->X = (RawPoint->X * pContext->CoeffA) + (RawPoint->Y * pContext->CoeffB) + pContext->CoeffC; CalibratedPoint->Y = (RawPoint->X * pContext->CoeffD) + (RawPoint->Y * pContext->CoeffE) + pContext->CoeffF;
Introduction In the evolving landscape of Windows hardware development, touch devices have transitioned from premium luxury items to standard peripherals. Whether in industrial control panels, medical displays, automotive infotainment systems, or rugged tablets, the accuracy of touch input is paramount. At the heart of this accuracy lies a critical, often overlooked component: calibration .
VOID ApplyCalibration(PTOUCH_POINT RawPoint, PTOUCH_POINT CalibratedPoint)