Unit EXT.IO2 / Stamp IO — Home Assistant Integration

Unit EXT.IO2 is an IO expansion unit built around the STM32F030 MCU. It communicates over I²C and exposes 8 independently configurable IO pins. Each pin supports digital input/output, ADC, servo control, and RGB LED control. The I²C device address is configurable, so multiple EXT.IO2 units can coexist on the same bus to expand IO capacity further. Typical use cases include multi-channel digital/analog signal acquisition, lighting control, and servo actuation.

Stamp IO is an IO expansion board that shares the same STM32F030-based design and I²C communication protocol as Unit EXT.IO2. It provides the same 8-channel IO expansion with identical per-pin mode support.

Both devices require an external host controller connected via I²C.

Prerequisites

• A host controller device (e.g., Atom series, Stamp series, Stick series, Core/Basic series)
• A running Home Assistant instance
• ESPHome Builder installed and enabled in Home Assistant

Getting Started

I²C Bus

The extio2 component depends on the I²C Bus component. Add it to your configuration and set the SDA/SCL pins to match your host controller.

# Example configuration entry for ESP32
i2c:
  sda: GPIOXX
  scl: GPIOXX
  scan: true

For example, when using an Atom Lite as the host controller:

# I2C Bus on Grove Port (HY2.0-4P)
i2c:
  sda: GPIO26
  scl: GPIO32

Hub Component

Add the extio2 external component and declare the hub before using any platform:

external_components:
  - source: github://m5stack/esphome-yaml/components@main
    components: [extio2]
    refresh: 0s

extio2:
  id: extio2_hub

Configuration Variables

• id (Optional, ID): Manually assign an ID to this hub instance.
• address (Optional, int): I²C device address. Defaults to 0x45.
• reset (Optional, boolean): Perform a software reset on startup. All pins are set to output mode, driving low. Defaults to true.
• pwm_freq (Optional, enum): Global PWM frequency shared by all channels. Defaults to 1kHz. Options:
  • 2kHz
  • 1kHz
  • 500Hz
  • 250Hz
  • 125Hz
• All options from I²C Device are also supported.

GPIO Pin

EXT.IO2 pins can be used anywhere ESPHome accepts a standard GPIO pin reference, such as switch, binary_sensor, and similar components.

# Digital output — switch
switch:
  - platform: gpio
    name: "EXT.IO2 GPIO 0"
    pin:
      extio2_id: extio2_hub
      number: 0
      mode:
        output: true

# Digital input — binary sensor
binary_sensor:
  - platform: gpio
    name: "EXT.IO2 GPIO 1"
    pin:
      extio2_id: extio2_hub
      number: 1

Pin Configuration Variables

• extio2_id (Required, ID): The ID of the EXT.IO2 hub.
• number (Required, int): Pin number, 0–7.
• inverted (Optional, boolean): Invert the pin logic. Defaults to false.

Sensor (ADC)

The sensor platform reads analog values from any of the 8 ADC-capable pins.

sensor:
  - platform: extio2
    extio2_id: extio2_hub
    name: "ADC Sensor 0"
    channel: ADC_0
    resolution: 12BIT
    update_interval: 5s

Configuration Variables

• extio2_id (Optional, ID): The ID of the EXT.IO2 hub.
• channel (Required, enum): ADC channel to read, ADC_0 through ADC_7.
• resolution (Optional, enum): ADC resolution. Defaults to 8BIT.
  • 8BIT: 8-bit resolution, range 0–255.
  • 12BIT: 12-bit resolution, range 0–4095.
• update_interval (Optional, Time): Polling interval. Defaults to 60s.
• All options from Sensor are also supported.

Output (PWM)

The output platform drives any pin as a PWM output. Duty cycle is expressed as a float from 0.0 to 1.0, mapped internally to 0–100%.

output:
  - platform: extio2
    extio2_id: extio2_hub
    id: pwm_ch0
    channel: PWM_0

light:
  - platform: monochromatic
    name: "PWM Light 0"
    output: pwm_ch0
    effects:
      - pulse:

Configuration Variables

• extio2_id (Optional, ID): The ID of the EXT.IO2 hub.
• id (Required, ID): ID for this output.
• channel (Required, enum): PWM channel to use, PWM_0 through PWM_7.
• All options from Float Output are also supported.

Number (Servo)

The number platform controls servos in two modes: angle (degrees) or pulse width (microseconds).

Angle Mode

Controls servo position by angle (0–180°).

number:
  - platform: extio2
    extio2_id: extio2_hub
    name: "Servo 0"
    type: angle
    channel: SERVO_0
    min_value: 0
    max_value: 180
    step: 3

Pulse Mode

Controls servo position by raw pulse width (microseconds).

number:
  - platform: extio2
    extio2_id: extio2_hub
    name: "Servo 1"
    type: pulse
    channel: SERVO_1
    min_value: 500
    max_value: 2500
    step: 100

Configuration Variables

• extio2_id (Optional, ID): The ID of the EXT.IO2 hub.
• type (Required, enum): Servo control mode.
  • angle: Control by angle.
  • pulse: Control by pulse width.
• channel (Required, enum): Servo channel to use, SERVO_0 through SERVO_7.
• min_value (Optional, float): Minimum value. Defaults to 0.0 (angle) or 500.0 (pulse).
• max_value (Optional, float): Maximum value. Defaults to 180.0 (angle) or 2500.0 (pulse).
• step (Optional, float): Step size. Defaults to 3.0 (angle) or 100.0 (pulse).
• All options from Number are also supported.

Light

The light platform supports two modes: a single RGB LED on a specified pin, or an addressable LED strip starting from pin 0.

Single RGB LED

Controls one RGB LED on the specified pin.

light:
  - platform: extio2
    extio2_id: extio2_hub
    name: "EXT.IO2 Light 2"
    type: light
    channel: LIGHT_2

Addressable LED Strip

Controls a consecutive run of RGB LEDs starting from pin 0. Supports all ESPHome addressable light effects.

light:
  - platform: extio2
    extio2_id: extio2_hub
    name: "LED Strip"
    type: addressable_light
    num_leds: 8

Configuration Variables

• extio2_id (Optional, ID): The ID of the EXT.IO2 hub.
• type (Required, enum): Light mode.
  • light: Single RGB LED.
  • addressable_light: Addressable LED strip.
• channel (Required for light type, enum): Pin to use, LIGHT_0 through LIGHT_7.
• num_leds (Required for addressable_light type, int): Number of LEDs, 1–8. Pins are assigned consecutively starting from pin 0.
• All options from Light are also supported.

Full Configuration Example

i2c:
  sda: GPIO2
  scl: GPIO1

extio2:
  id: extio2_hub
  address: 0x45
  reset: true
  pwm_freq: 1kHz

# GPIO — digital output
switch:
  - platform: gpio
    name: "EXT.IO2 GPIO 0"
    pin:
      extio2_id: extio2_hub
      number: 0
      mode:
        output: true

# GPIO — digital input
binary_sensor:
  - platform: gpio
    name: "EXT.IO2 GPIO 1"
    pin:
      extio2_id: extio2_hub
      number: 1
      mode:
        input: true
        pullup: true

# ADC sensor
sensor:
  - platform: extio2
    extio2_id: extio2_hub
    name: "ADC Sensor 2"
    channel: ADC_2
    resolution: 12BIT
    update_interval: 5s

# PWM output used as monochromatic light
output:
  - platform: extio2
    extio2_id: extio2_hub
    id: pwm_ch3
    channel: PWM_3

light:
  - platform: monochromatic
    name: "PWM Light 3"
    output: pwm_ch3
    effects:
      - pulse:

  # Single RGB LED
  - platform: extio2
    extio2_id: extio2_hub
    name: "RGB Light 6"
    type: light
    channel: LIGHT_6

  # Addressable LED strip (all 8 pins)
  - platform: extio2
    extio2_id: extio2_hub
    name: "LED Strip"
    type: addressable_light
    num_leds: 8

number:
  # Servo — angle control
  - platform: extio2
    extio2_id: extio2_hub
    name: "Servo 4"
    type: angle
    channel: SERVO_4

  # Servo — pulse width control
  - platform: extio2
    extio2_id: extio2_hub
    name: "Servo 5"
    type: pulse
    channel: SERVO_5