Kmdf Hid Minidriver For Touch I2c Device Calibration |work|

A typical Windows desktop application:

A specialized calibration tool calculates new offsets.

: Scales raw touch digitizer resolution to match the actual display resolution.

NTSTATUS RetrieveCalibrationFromACPI( _In_ WDFDEVICE Device, _Out_ PVOID CalibrationBuffer, _In_ ULONG BufferSize ) NTSTATUS status; ACPI_EVAL_INPUT_BUFFER_COMPLEX inputBuffer = 0 ; PACPI_EVAL_OUTPUT_BUFFER outputBuffer = NULL; ULONG outputLength = 0; // 1. Initialize ACPI input arguments with the Touch _DSM UUID inputBuffer.Signature = ACPI_EVAL_INPUT_BUFFER_COMPLEX_SIGNATURE; inputBuffer.MethodNameAsUlong = (ULONG)'MSD_'; // _DSM reversed inputBuffer.ArgumentCount = 4; // (Fill out UUID, Revision, Function Index, and Empty Package arguments here...) // 2. Send the IOCTL_ACPI_EVAL_METHOD to the underlying bus status = WdfIoTargetSendIoctlSynchronously( WdfDeviceGetIoTarget(Device), NULL, IOCTL_ACPI_EVAL_METHOD, &inputMemoryDescriptor, &outputMemoryDescriptor, NULL, NULL ); if (NT_STATUS_IS_SUCCESS(status)) // Parse outputBuffer down to coefficients and copy to CalibrationBuffer return status; Use code with caution. 4. Injecting Calibration into the HID Parsing Pipeline

If you want to dive deeper into implementing this architecture, tell me: kmdf hid minidriver for touch i2c device calibration

The driver updates its internal transformation matrix and writes the new values to the registry for the next boot. 5. Best Practices for I2C Touch Drivers

HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\TOUCH\CalibrationData .

Accurate coordinate mapping requires proper calibration parameters for the driver to convert raw touch coordinates to the Windows virtual display screen. While modern precision touchpad devices using buses like I2C are often handled by Microsoft's inbox drivers, scenarios necessitating a custom KMDF minidriver also impose the need for manual or semi-automatic calibration methods.

To update calibration values on the fly (e.g., during a user-facing calibration wizard), the driver should expose a custom Input/Output Control (IOCTL) code. When a user-space application calculates a new matrix, it sends the data down to the driver using DeviceIoControl . The driver updates its local memory variables and writes the new values back to the registry. 5. Advanced Techniques: Dynamic Baseline Calibration Initialize ACPI input arguments with the Touch _DSM

Apply the math discussed in Section 3.

Ensure your HID Report Descriptor accurately reflects the "Logical Minimum" and "Logical Maximum" after calibration is applied. Conclusion

The touch device sends HID Input Reports (touch points). In EvtHidDeviceGetReport or when the HID class driver calls your minidriver to retrieve a report, you:

TouchMaxX : Physical maximum X value reported by the digitizer firmware. Injecting Calibration into the HID Parsing Pipeline If

Windows stores calibration data for touch devices in a specific registry location. If your driver needs to apply a static offset or scale factor at boot, it should query this path or its own device parameters.

A HID minidriver is a specialized driver that enables a HID device to communicate with the Windows operating system. HID devices, such as touchscreens, mice, and keyboards, are designed to provide an intuitive interface for users to interact with their computers. The HID minidriver acts as a bridge between the device and the operating system, facilitating data exchange and device control.

Ensure that I2C read errors are handled gracefully without crashing the system.

// Define the HID report descriptor parsing function VOID HidReportDescriptorParse(WDFDEVICE device, PVOID reportDescriptor, ULONG reportDescriptorLength) // Parse the HID report descriptor HID_REPORT_DESCRIPTOR* hidReportDescriptor; hidReportDescriptor = (HID_REPORT_DESCRIPTOR*)reportDescriptor; // ...