Kmdf Hid Minidriver For Touch I2c Device Calibration 'link' -

For a KMDF HID minidriver targeting an I2C touch device, calibration is typically handled at the operating system level via standard Windows tools or by injecting specific registry parameters that the driver reads to modify incoming raw coordinates. 1. Identify Calibration Registry Path

Calibration data models

  • Affine transform (3x3 homogeneous matrix or 2x2+offset): Handles rotation, uniform/non-uniform scale and translation.
  • Higher-order polynomial warp (2D polynomials): For moderate nonlinearity; e.g., bicubic polynomials mapping (x_raw,y_raw) -> (x_disp,y_disp).
  • Piecewise lookup tables (LUTs) / grid-based warping: Divide surface into grid cells; each cell stores correction vectors for interpolation (bilinear or bicubic). Good for spatially varying distortions.
  • Thin-plate spline or RBF interpolation: Smooth, continuous warps defined by control points for more complex distortions.
  • Per-contact calibration parameters: Size- or pressure-dependent offsets to account for centroid bias for fingers vs stylus.

[MyTouchCalib.AddReg] HKR,,"LowerFilters",0x00010000,"MyTouchCalib" kmdf hid minidriver for touch i2c device calibration

#include <wdf.h>
#include <hid.h>

    

  • Provide an atomic write flow to persist calibration: write to device NV and then to registry backup; confirm CRC.
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  • If NV writes are slow or can fail, use async workers and present an interim state to minimize blocking.
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Registry Entries: Windows stores specific calibration results in the registry at: HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\TOUCH\CalibrationData. Implementation and Troubleshooting For a KMDF HID minidriver targeting an I2C


WDFKEY hKey;
WdfDeviceOpenRegistry(Device, PLUGPLAY_REGKEY_DEVICE, &hKey);
// Read REG_BINARY "CalibCoeffs" -> store in device context
WdfRegistryClose(hKey);



    

  • HidStart: Starts the minidriver and initializes the touch device.
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  • HidStop: Stops the minidriver and releases any resources allocated for the touch device.
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  • HidRead: Reads data from the touch device, such as touch coordinates and button presses.
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  • HidWrite: Writes data to the touch device, such as calibration settings.
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Capture logs via TraceView.exe and correlate with HID class driver traces. [MyTouchCalib