A tool to inspect the raw HID reports reaching the OS.
The KMDF driver creates an I/O queue and provides an EVT_WDF_IO_QUEUE_IO_DEVICE_CONTROL callback function to branch to custom IOCTL handlers.
Implementing a software-based low-pass or Kalman filter directly in the KMDF driver to smooth out coordinate jitter.
NTSTATUS Status; WDFKEY TargetKey; ULONG XOffset = 0, YOffset = 0; DECLARE_CONST_UNICODE_STRING(ValueName, L"CalibrationOffset"); Status = WdfDeviceOpenRegistryKey(Device, PLUGPLAY_REGKEY_DEVICE, KEY_READ, WDF_NO_OBJECT_ATTRIBUTES, &TargetKey); if (NT_SUCCESS(Status)) // Read calibration parameters here into driver context structures WdfRegistryQueryULong(TargetKey, &ValueName, &XOffset); WdfRegistryClose(TargetKey); Use code with caution. 3. The Calibration Coordinate Mapping Matrix kmdf hid minidriver for touch i2c device calibration
Calibration fundamentally relies on mathematical transformation. The raw coordinates received from the I2C controller must be mapped to target screen coordinates The 3-Point Calibration Algorithm
The actual size of the panel in millimeters. Usage Page: Digitizers (0x0D). Usage: Touch Screen (0x04).
KMDF HID Minidriver for Touch I2C Device Calibration: A Technical Guide A tool to inspect the raw HID reports reaching the OS
By using a lower filter driver model, this technique allows an OEM to supply just a small, custom KMDF driver that slots in beneath Microsoft's mshidkmdf.sys class driver. This approach often uses the vhidmini2 sample as a starting point. The minidriver registers with the HID class driver, receives touch input from the I²C hardware, and then packages it into HID reports for the system to digest.
A good calibration algorithm computes transformation coefficients (scale factors, skew, rotation angle, and translation offsets) to correct the raw data accurately.
Done by the user or calibration software. Parameters are stored in the Windows Registry or within the touch controller. B. The Calibration Process (HID Feature Reports) NTSTATUS Status; WDFKEY TargetKey; ULONG XOffset = 0,
Windows will ignore your calibrated data if the HID Report Descriptor does not correctly specify a Touch Screen or Multi-touch Digitizer application collection.
Ycal=D⋅Xraw+E⋅Yraw+Fcap Y sub c a l end-sub equals cap D center dot cap X sub r a w end-sub plus cap E center dot cap Y sub r a w end-sub plus cap F
Touch device calibration generally falls into two paradigms: firmware-level calibration and driver-level software calibration. 1. Firmware-Level Calibration (Vendor Commands)
By implementing a well-structured KMDF HID minidriver, developers can ensure that I2C touch devices are responsive and accurately calibrated, providing a seamless experience for Windows users.
The KMDF HID minidriver for touch I2C device calibration consists of the following components: