> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kode.diy/llms.txt
> Use this file to discover all available pages before exploring further.

# IO Expander

> Learn to control the programmable pins of the IO expander.

# Features

Although all the **important signals** of the components of the Kode Dot are connected to the **pins of the ESP32-S3,** there are some **less important signals** that do not fit.

The IO expander is a component that has **16 programmable pins** and to which the rest of the signals are connected that, or are of **low speed** or that **are not very relevant.**

## Connection diagram

The pins of the expander are controlled by the ESP32-S3 through the **I2C bus.** In addition, it has an **interrupt pin** that is connected to the ESP32-S3 to know when there has been a change in one of its pins.

The IO expander is connected to the ESP32-S3 in the following way:

| Expander  | ESP32-S3 |
| --------- | -------- |
| SDA       | GPIO48   |
| SCL       | GPIO47   |
| Interrupt | GPIO18   |

<Note>The expander has the address 0x20 on the I2C bus.</Note>

The signals of the different components of the Kode Dot that are connected to the expander are:

| Signal                         | Expander |
| ------------------------------ | -------- |
| Magnetometer - INT             | EXP0     |
| RTC - INTB                     | EXP1     |
| RTC - INTA                     | EXP2     |
| Amplifier - SD                 | EXP3     |
| Power supply - 3V3 peripherals | EXP4     |
| Battery indicator - GPOUT      | EXP5     |
| Pad - Up                       | EXP6     |
| Pad - Left                     | EXP7     |
| Pad - Down                     | EXP8     |
| Button - Down                  | EXP9     |
| PMIC - INT                     | EXP10    |
| Pad - Right                    | EXP11    |
| IMU - INT2                     | EXP12    |
| IMU - INT1                     | EXP13    |
| microSD - CD                   | EXP14    |
| Screen - TP INT                | EXP15    |

Most of the signals are interrupt signals of the different integrated circuits or buttons and in the examples of the following sections it is implemented the reading of these signals.

## Recommended libraries

### Arduino

* [ESP32\_IO\_Expander](https://github.com/esp-arduino-libs/ESP32_IO_Expander)

### ESP-IDF

* [esp\_io\_expander\_tca95xx\_16bit](https://components.espressif.com/components/espressif/esp_io_expander_tca95xx_16bit)

## Example code

With this code you can test the operation of the expander of pins. When you press the **down button,** a message will be printed on the **serial monitor.**

```cpp expander_test.ino lines icon="microchip"	 theme={null}
/**
 * Reads and displays the status of signals connected to a TCA95XX_16BIT I/O expander via I2C.
 * Configures pins as inputs or outputs and updates the reading every second.
 * Shows each pin's name and state on the serial monitor.
 */
/* ───────── KODE | docs.kode.diy ───────── */

#include <esp_io_expander.hpp> /* Library to control I/O expanders on ESP32 */

#define I2C_SCL_PIN     (47)   /* I2C bus SCL pin */
#define I2C_SDA_PIN     (48)   /* I2C bus SDA pin */
#define I2C_ADDR        (0x20) /* I2C address of the expander */

esp_expander::Base *expander = nullptr; /* Pointer to expander object */

/* Descriptive signal names */
const char* signalNames[14] = {
  "Magnetometer - INT",        // EXP0
  "RTC - INTB",                // EXP1
  "RTC - INTA",                // EXP2
  "Battery Indicator - GPOUT", // EXP5
  "Pad - Up",                  // EXP6
  "Pad - Left",                // EXP7
  "Pad - Down",                // EXP8
  "Button - Down",             // EXP9
  "PMIC - INT",                // EXP10
  "Pad - Right",               // EXP11
  "IMU - INT2",                // EXP12
  "IMU - INT1",                // EXP13
  "microSD - CD",              // EXP14
  "Display - TP INT"           // EXP15
};

void setup() {
  Serial.begin(115200); /* Starts serial communication at 115200 baud */
  Serial.println("Expander polling test start.");

  /* Initializes the expander at the configured I2C address */
  expander = new esp_expander::TCA95XX_16BIT(I2C_SCL_PIN, I2C_SDA_PIN, I2C_ADDR);
  expander->init();
  expander->begin();

  /* Sets pins 3 and 4 as outputs */
  expander->multiPinMode(IO_EXPANDER_PIN_NUM_3 | IO_EXPANDER_PIN_NUM_4, OUTPUT);

  /* Sets all other pins as inputs */
  expander->multiPinMode(IO_EXPANDER_PIN_NUM_0 | IO_EXPANDER_PIN_NUM_1 | IO_EXPANDER_PIN_NUM_2 |
                         IO_EXPANDER_PIN_NUM_5 | IO_EXPANDER_PIN_NUM_6 | IO_EXPANDER_PIN_NUM_7 |
                         IO_EXPANDER_PIN_NUM_8 | IO_EXPANDER_PIN_NUM_9 | IO_EXPANDER_PIN_NUM_10 |
                         IO_EXPANDER_PIN_NUM_11 | IO_EXPANDER_PIN_NUM_12 | IO_EXPANDER_PIN_NUM_13 |
                         IO_EXPANDER_PIN_NUM_14 | IO_EXPANDER_PIN_NUM_15, INPUT);

  /* Sets controlled outputs to LOW */
  expander->digitalWrite(IO_EXPANDER_PIN_NUM_3, LOW); /* Amplifier - SD */
  expander->digitalWrite(IO_EXPANDER_PIN_NUM_4, LOW); /* Power Supply - 3V3 peripherals */
}

int level[14] = {0}; /* Input states */

void loop() {
  /* Reads the state of each input pin on the expander */
  level[0] = expander->digitalRead(0);
  level[1] = expander->digitalRead(1);
  level[2] = expander->digitalRead(2);
  level[3] = expander->digitalRead(5);
  level[4] = expander->digitalRead(6);
  level[5] = expander->digitalRead(7);
  level[6] = expander->digitalRead(8);
  level[7] = expander->digitalRead(9);
  level[8] = expander->digitalRead(10);
  level[9] = expander->digitalRead(11);
  level[10] = expander->digitalRead(12);
  level[11] = expander->digitalRead(13);
  level[12] = expander->digitalRead(14);
  level[13] = expander->digitalRead(15);

  /* Displays the status of each signal on the serial monitor */
  Serial.println("=== Pin Status ===");
  for (int i = 0; i < 14; i++) {
    Serial.printf("EXP%02d: %d - %s\n", i, level[i], signalNames[i]);
  }
  Serial.println();

  delay(1000); /* Waits 1 second before the next read */
}
```

## Download of examples

You can test the example codes using the Arduino IDE or the ESP-IDF IDE or download the codes in our drive:

[IO expander examples](https://drive.google.com/drive/folders/1nJHAeJOtqmLtWnhrUvgWu9GuijLvPg9s)