Touchpad Sensor → Microcontroller (Firmware) → USB/I2C → HID Driver → Input Subsystem → User Apps
We presented a complete, HID-compliant touchpad driver supporting multi-touch with tracking IDs, low latency, and power management. The implementation works across major OSes with minor adjustments. Our code is available as a reference for embedded touchpad developers. Future work includes adding haptic feedback support and machine-learning-based gesture recognition.
: A failed Windows or firmware update can break the handshake between the hardware and the OS. hid compliant touchpad driver
static unsigned char touchpad_rdesc[] = 0x05, 0x0D, // Usage Page (Digitizer) 0x09, 0x05, // Usage (Touch Pad) 0xA1, 0x01, // Collection (Application) 0x85, 0x01, // Report ID 1 0x09, 0x22, // Usage (Finger) 0xA1, 0x02, // Collection (Logical) 0x09, 0x42, // Usage (Tip Switch) 0x15, 0x00, // Logical Minimum (0) 0x25, 0x01, // Logical Maximum (1) 0x75, 0x01, // Report Size (1) 0x95, 0x01, // Report Count (1) 0x81, 0x02, // Input (Data,Var,Abs) 0x09, 0x51, // Usage (Contact Identifier) 0x75, 0x08, // Report Size (8) 0x95, 0x01, // Report Count (1) 0x81, 0x02, // Input (Data,Var,Abs) 0x05, 0x01, // Usage Page (Generic Desktop) 0x09, 0x30, // Usage (X) 0x09, 0x31, // Usage (Y) 0x16, 0x00, 0x00, // Logical Minimum (0) 0x26, 0xFF, 0x0F, // Logical Maximum (4095) 0x75, 0x10, // Report Size (16) 0x95, 0x02, // Report Count (2) 0x81, 0x02, // Input (Data,Var,Abs) 0xC0, // End Collection 0x05, 0x0D, // Usage Page (Digitizer) 0x09, 0x54, // Usage (Contact Count) 0x95, 0x01, // Report Count (1) 0x75, 0x08, // Report Size (8) 0x81, 0x02, // Input (Data,Var,Abs) 0xC0, // End Collection ;
struct input_dev *input = hdev->input; int contact_count = data[0]; // First byte: number of touches int offset = 1; int i, slot, id; for (i = 0; i < contact_count && offset + 5 < size; i++) (data[offset + 3] << 8)); u16 y = (data[offset + 4] Future work includes adding haptic feedback support and
The Linux kernel’s hid-multitouch driver handles generic HID multi-touch devices, but custom hardware often needs vendor-specific quirks. Windows Precision Touchpad (WTP) standard further defines gesture processing. Our work implements a driver that can optionally bypass OS generic drivers when low-level control is needed.
// Send sleep command to touchpad over HID u8 sleep_cmd[] = 0x00, 0x02; // Vendor-specific sleep opcode hid_hw_raw_request(hdev, 0x02, sleep_cmd, 2, HID_FEATURE_REPORT, HID_REQ_SET_REPORT); return 0; // Vendor-specific sleep opcode hid_hw_raw_request(hdev
You might wonder if you should use the generic driver or download a specific one from your laptop manufacturer’s website (e.g., Dell, HP, or Lenovo).
Each input report contains contact count followed by touch data.
The simplest fix is often to force Windows to redetect the hardware.
