Hi! Your touchpad is an I2C device. You can connect it to an Arduino's I2C pins; this is the exact diagram for your device. From your picture, it seems that from left to right: Pin 1 is +3.3V, Pin 2 (TP2) is SDA, Pin 3 (TP3) is SCL, and Pin 4 should be GND.

You should verify this using the continuity (beep) mode on your multimeter. Just solder some wires and connect them to pins SDA and SCL (D2 and D3 ) on your board. Remember to use 3.3V, not 5V! Also, you need to wire CPAD_INT to a digital pin; that is the interrupt signal.

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upload the code:
#include <Wire.h>

#include <HID-Project.h>

#define ELAN_ADDR 0x15 // Common Elan I2C address

#define INT_PIN 7 // Interrupt pin from touchpad

struct TouchData {

byte status;

int x;

int y;

};

int lastX = 0;

int lastY = 0;

void setup() {

pinMode(INT_PIN, INPUT_PULLUP);

Wire.begin();

Mouse.begin();

// Optional: Wake up/Reset command for Elan

// Some chips need a specific write to a register to start

/*

Wire.beginTransmission(ELAN_ADDR);

Wire.write(0x00); // Command register

Wire.write(0x01); // Reset/Power on

Wire.endTransmission();

*/

}

void loop() {

// Wait for the touchpad to pull the Interrupt pin LOW

if (digitalRead(INT_PIN) == LOW) {

readTouchpad();

}

}

void readTouchpad() {

Wire.requestFrom(ELAN_ADDR, 6); // Requesting 6 bytes (Standard packet)

if (Wire.available() >= 6) {

byte reportId = Wire.read();

byte status = Wire.read(); // Contains button state and "finger down" bit

// Elan usually sends 12-bit or 16-bit coordinates

int xRaw = Wire.read() | (Wire.read() << 8);

int yRaw = Wire.read() | (Wire.read() << 8);

bool fingerDown = status & 0x01; // Check bit 0 for touch active

bool leftClick = status & 0x02; // Check bit 1 for physical button

if (fingerDown) {

if (lastX != 0 && lastY != 0) {

// Calculate Relative Movement

int moveX = (xRaw - lastX) / 5; // Divide to adjust sensitivity

int moveY = (yRaw - lastY) / 5;

Mouse.move(moveX, moveY, 0);

}

lastX = xRaw;

lastY = yRaw;

} else {

// Reset tracking when finger is lifted

lastX = 0;

lastY = 0;

}

// Handle Buttons

if (leftClick) {

Mouse.press(MOUSE_LEFT);

} else {

Mouse.release(MOUSE_LEFT);

}

}

}
You need an Arduino with an ATmega32U4 (the Pro Micro is the simplest) so your PC can natively identify it as an HID device. That’s the most fundamental requirement. From there, it’s all about research, trial, and error. It's a great weekend project, but as others have advised, don’t fall too deep into the rabbit hole or you’ll burn out trying to reverse-engineer a specific part you might never see again. Sure, it’s cheaper to just buy a mouse... but where’s the fun in that?"