STMPE610 Resistive Touch Controller Explained

This example shows how to read touch coordinates from an STMPE610 resistive touch controller using I²C or SPI. The sketch detects touch events, reads X/Y/Z pressure data, and prints everything to Serial for debugging and calibration.

The STMPE610 is a very handy chip if you’re working with resistive touch screens. Instead of reading raw analog signals yourself, it handles all the touch processing and gives you clean digital data over I²C or SPI.

What this example does

This sketch continuously monitors the touch controller and:

Detects when the screen is touched
Reads X and Y coordinates
Reads pressure (Z value)
Prints everything to the Serial Monitor
Clears the interrupt flags

It’s basically a raw touch reader, perfect for testing and calibration before building a UI.

Supported communication modes

The STMPE610 supports three communication options:

1. I²C (default in this example)

Adafruit_STMPE610 touch = Adafruit_STMPE610();

Simplest wiring
Uses ESP32 I²C pins
Slightly slower than SPI

2. Hardware SPI

Adafruit_STMPE610 touch = Adafruit_STMPE610(STMPE_CS);

Faster communication
Uses ESP32 hardware SPI pins

3. Software SPI

Adafruit_STMPE610 touch = Adafruit_STMPE610(STMPE_CS, STMPE_SDI, STMPE_SDO, STMPE_SCK);

Flexible pin selection
Slower than hardware SPI

ESP32 wiring (recommended)

I²C wiring (simplest)

VCC → 3.3V
GND → GND
SDA → GPIO21
SCL → GPIO22
MODE → GND (IMPORTANT for I²C)

SPI wiring (faster)

VCC → 3.3V
GND → GND
MOSI → GPIO23
MISO → GPIO19
SCK → GPIO18
CS → any GPIO (e.g. GPIO5)
MODE → 3.3V (IMPORTANT for SPI)

👉 After changing MODE, you must power cycle the board.

Code walkthrough

Creating the touch object

Adafruit_STMPE610 touch = Adafruit_STMPE610();

This initializes the controller in I²C mode by default.

`setup()`

Serial.begin(9600);
Serial.println("Adafruit STMPE610 example");

Standard Serial output for debugging.

Initializing the controller

if (! touch.begin()) {
  Serial.println("STMPE not found!");
  while(1);
}

If the chip is not detected:

Wrong wiring
Wrong mode (I²C vs SPI)
Wrong address

I²C address options

touch.begin(0x41); // default
touch.begin(0x44); // if A0 = HIGH

Most boards use 0x41.

The main loop

Detecting a touch

if (touch.touched()) {

This checks if the screen is currently being pressed.

Reading touch data

touch.readData(&x, &y, &z);

This gives you:

x → horizontal position
y → vertical position
z → pressure

Example output

1->(1234, 2048, 56)

Meaning:

X = 1234
Y = 2048
Pressure = 56

Buffer handling

while (! touch.bufferEmpty()) {

The STMPE610 stores multiple touch samples in a buffer.

This loop:

Reads all available samples
Prevents data loss
Ensures smooth tracking

Clearing interrupts

touch.writeRegister8(STMPE_INT_STA, 0xFF);

This resets interrupt flags.

Not always required, but good practice in polling setups.

Understanding the Z (pressure) value

The z value tells you how hard the screen is pressed.

Typical usage:

Ignore very low values → noise
Use threshold to detect valid touches

Example:

if (z > 10) {
  // valid touch
}

Important practical notes

1. Resistive touch ≠ pixel coordinates

Raw values are not screen pixels.

You must map them:

mappedX = map(x, minX, maxX, 0, screenWidth);
mappedY = map(y, minY, maxY, 0, screenHeight);

Calibration is required.

2. Orientation matters

Depending on display rotation:

X and Y may be swapped
Values may need inversion

3. Buffer vs single read

Using:

bufferEmpty()

is better than single reads because:

You don’t miss fast touches
Movement feels smoother

4. MODE pin is critical

I²C → MODE = GND
SPI → MODE = 3.3V

Wrong setting = no communication.

How to use this in real projects

Once this basic example works, you can:

Build touch buttons
Create menus or UI
Combine with TFT display (ILI9341, ST7789, etc.)
Use gestures (swipe, drag)
Add touch calibration screen

Common mistakes

Forgetting to power cycle after changing MODE
Using wrong I²C address
Not mapping raw coordinates
Ignoring pressure (z) → false touches
Not emptying buffer → laggy response

Final thoughts

The STMPE610 takes all the messy analog work of resistive touch and turns it into clean digital data. This example is simple, but it gives you everything you need to: