Overview

The XPT2046 is a 4-wire resistive touchscreen controller IC manufactured by Shenzhen XPT (fully pin-compatible with the Texas Instruments ADS7843 / ADS7846). Commonly pre-soldered on the back of 2.4", 2.8", 3.2", and 3.5" color TFT LCD breakout boards (such as ILI9341, ST7789, or HX8357 displays), it converts mechanical touch pressure on resistive glass overlays into precise digital X and Y screen coordinates.

Integrating a 12-bit Successive Approximation Register (SAR) ADC, internal $2.5\text{V}$ voltage reference, low-on-resistance internal MOSFET switches ($R_{ON} \approx 5\ \Omega$), and a synchronous SPI interface (up to 2.5 MHz), the XPT2046 also includes an active-low touch interrupt output (T_IRQ) that pulls Low whenever a stylus or finger presses the screen.

Quick reference

Pinout (TSSOP-16 Package & TFT Module Headers)

             ┌───┴───┐
          X+ ─┤ 1   16├─ DCLK
          Y+ ─┤ 2   15├─ CS
          X- ─┤ 3   14├─ DIN (MOSI)
          Y- ─┤ 4   13├─ BUSY
         GND ─┤ 5   12├─ DOUT (MISO)
        VBAT ─┤ 6   11├─ PENIRQ (T_IRQ)
        AUX  ─┤ 7   10├─ VREF
         VCC ─┤ 8    9├─ VCC
             └───────┘

Specifications

Command Control Byte Format

To initiate a 12-bit ADC conversion, the host MCU transmits an 8-bit Control Byte over SPI:

• Bit 7: Start Bit (Must be 1).
• Bits 6–4: Channel Select (101 = X-Position, 001 = Y-Position, 011 = $Z_1$ Touch Pressure, 100 = $Z_2$ Touch Pressure).
• Bit 3: Resolution (0 = 12-Bit Mode, 1 = 8-Bit Mode).
• Bit 2: SER/$\bar{DFR}$ Mode (0 = Differential Reference, 1 = Single-Ended Reference).
• Bits 1–0: Power-Down Mode (00 = Low power with PENIRQ enabled).

Command Byte Table

Wiring (ILI9341 SPI TFT with Touch)

Example (Arduino XPT2046_Touchscreen Library)

#include <SPI.h>
#include <XPT2046_Touchscreen.h>

#define CS_PIN  4
#define TIRQ_PIN 2

// Initialize XPT2046 on CS_PIN 4 with Hardware Interrupt on TIRQ_PIN 2
XPT2046_Touchscreen ts(CS_PIN, TIRQ_PIN);

void setup() {
  Serial.begin(115200);
  ts.begin();
  ts.setRotation(1); // Set orientation to match TFT screen rotation
  Serial.println("XPT2046 Touch Controller Ready");
}

void loop() {
  if (ts.touched()) {
    TS_Point p = ts.getPoint();

    Serial.print("Touch Detected! Raw X: "); Serial.print(p.x);
    Serial.print(" | Raw Y: "); Serial.print(p.y);
    Serial.print(" | Pressure Z: "); Serial.println(p.z);
  }
  delay(100);
}

Common mistakes

• Exceeding 2.5 MHz SPI clock frequency: The XPT2046 SPI interface is rated for max 2.5 MHz. If sharing the SPI bus with high-speed TFT display drivers (like ILI9341 running at 40 MHz), the MCU must reduce SPI clock frequency down to $\le 2.5\text{ MHz}$ when asserting T_CS.
• Confusing raw ADC counts with pixel coordinates: The XPT2046 returns raw 12-bit ADC values ($~200 \dots 3800$). Map raw coordinates to screen pixel dimensions ($320 \times 240$) using 2-point calibration in code.

Notes

• XPT2046 vs FT6236: XPT2046 handles resistive single-point touch panels over SPI; FT6236 handles capacitive multi-touch glass panels over $I^2C$.