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Arduino Port Expander

With this sketch you can control pins of a remote Arduino board through ESPHome. The Arduino acts as a port expander, allowing you to use more pins than a standard ESP8266/ESP32 has.

Local Image

The Arduino is connected to the ESP via I²C. Most Arduinos use the A4 and A5 pins for the I²C bus so those pins are not available to read from ESPHome. It is recommended to use a 3.3V I/O level Arduino, however using 5V Arduinos seems to work too. In the latter case you should power your 5V Arduino with 3.3V otherwise you will need a level converter for the I²C bus.

Currently it is supported:

  • reading digital inputs
  • reading analog inputs
  • writing digital outputs

The Arduino sketch can be retrieved from here you can rename it to .ino and use the Arduino IDE to program it.

To setup the external component add the external component definition to your yaml:

external_components:
  source: github://glmnet/esphome-components
  components: [arduino_port_expander]

Setup your I²C Bus:

i2c:

By default ESP8266 uses SDA pin GPIO4 which you need to connect to Arduino's A4 and the SCL is GPIO5 which goes to Arduino's A5.

Then create a arduino_port_expander component hub, this will be the main component we will be referencing later when creating individual IOs.

arduino_port_expander:
  id: ape1 # must identify somehow to later use
  address: 0x08
  analog_reference: DEFAULT

By default the I²C address is 0x08 but you can change it on the Arduino sketch so you can have more devices on the same bus.

analog_reference can be DEFAULT or INTERNAL. Default is INTERNAL. See Arduino analogReference() function for details.

reference_voltage is the maximum value that can be measured. If the analog_reference is DEFAULT, then this should be the voltage that your Arduino board runs at, either 5 (default) or 3.3. If the analog_reference is INTERNAL, then this will be 1.1 (default) or 2.56. See the analogReference() link for details.

gpio pins

Use pins as any other port expander in ESPHome, you can use it in almost every place a pin is needed:

binary_sensor:
  - platform: gpio
    pin:
      arduino_port_expander: ape1
      number: 2
      mode:
        input: true # defaults to False
        output: false # defaults to False
        pullup: true # defaults to False

You can use any PIN from 0 to 13 or A0 to A3 (A4 and A5 are used for I²C and A6 and A7 do not support internal pull up). For A0 use 14, A1, 15 and so on.

Note: Arduino PIN 13 usually has a LED connected to it and using it as digital input with the built in internal pull up might be problematic, using it as an output is preferred.

Sensor

Sensors allows for reading the analog value of an analog pin, those are from A0 to A7 except for A4 and A5 which are used for the i2c connection.

Arduino analog inputs measures voltage. By default the sketch is configured to use the Arduino internal VREF reference setup to 1.1 volt, so higher voltages are read as 1023. You can configure Arduino to compare the voltage to VIN voltage, this voltage might be 5 volts or 3.3 volts, depending on how you are powering it. See the main component config to declare which voltage your board uses.

raw: true will return the raw measured value from 0-1023 (the value returned by the Arduino analogRead function) instead of the calculated voltage.

sensor:
  - platform: arduino_port_expander
    id: sx
    pin: A0
    name: Ardu A0
    update_interval: 10s