Log raw I2C values during development to ensure your calibration algorithm maintains at least a 20:1 SNR.
Where $A, B, C, D, E, F$ are the calibration coefficients.
The calibration process should not be a static, one-time event at the factory. Instead, implement a multi-staged approach:
I2C (Inter-Integrated Circuit) is a low-speed, two-wire bus. Unlike USB, it lacks plug-and-play enumeration and standardized power management. Windows handles this through the ( HIDI2C.sys ). However, for custom touch controllers (e.g., from Goodix, ELAN, or Cypress), a vendor minidriver is required. kmdf hid minidriver for touch i2c device calibration best
If the driver is functioning but the alignment is slightly off, leverage the built-in Windows Calibration utility
: Explicitly defines the maximum horizontal and vertical resolution reporting constraints.
A best-in-class KMDF minidriver adds post-calibration filtering: Log raw I2C values during development to ensure
Here is the step-by-step implementation of a calibration subroutine within a KMDF HID minidriver for an I2C touch device.
For standard I2C touch devices, Approach A (Firmware Handled) is preferred. However, the driver must implement Approach B (Driver Handled) as a fallback if the firmware lacks processing capability.
: Ensure the wReportDescLength and wReportDescRegister fields in your HID Descriptor are precise. Errors here often cause inverted axes or touches that only map to a small portion of the screen. However, for custom touch controllers (e
On reboot, EvtDevicePrepareHardware reads this property. If present, your driver sends a Feature Report to the I2C device to inject these coefficients before touch reporting starts.
How do you know your KMDF HID minidriver calibration is truly best ? Run these tests:
NTSTATUS I2cSendCalibrationCommand( _In_ WDFDEVICE Device, _In_ BYTE CalibrationCmdRegister, _In_ BYTE CalibrationPayload ) PDEVICE_CONTEXT pDeviceContext = DeviceGetContext(Device); WDF_MEMORY_DESCRIPTOR inputDescriptor; NTSTATUS status; // Construct the I2C payload packet: [Register Address, Command Value] BYTE writeBuffer[2] = CalibrationCmdRegister, CalibrationPayload ; WdfMemoryDescriptorInitializeBuffer( &inputDescriptor, (PVOID)writeBuffer, sizeof(writeBuffer) ); // Synchronously send the write request down to the SPB controller status = WdfIoTargetSendWriteSynchronously( WdfDeviceGetIoTarget(Device), NULL, &inputDescriptor, NULL, NULL, NULL ); if (!NT_SUCCESS(status)) TraceEvents(TRACE_LEVEL_ERROR, TRACE_DRIVER, "I2C Calibration Write Failed: %!STATUS!", status); return status; Use code with caution. 3. Handling Calibration via HID Feature Reports