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.

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.

You need to download arduino_port_expander.h and include the arduino_port_expander.h in the ESPHome configuration.

esphome:
  # ...
  includes:
      - arduino_port_expander.h

Setup your I²C Bus and assign it an id:

i2c:
  id: i2c_component

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 custom_component, this will be the main component we will be referencing later when creating individual IOs.

custom_component:
  - id: ape
    lambda: |-
      auto ape_component = new ArduinoPortExpander(i2c_component, 0x08);
      return {ape_component};

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.

Now it is time to add the ports.

Binary_Sensor

When adding binary sensors the pins are configured as INPUT_PULLUP, 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)

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.

To setup binary sensors, create a custom platform as below, list in braces all the sensors you want, in the example below two binary sensors are declared on pin 9 and A0 (number 14)

Then declare the ESPHome reference of the binary sensor in the same order as declared in the lambda:

binary_sensor:
  - platform: custom
    lambda: |-
      return {ape_binary_sensor(ape, 9),
              ape_binary_sensor(ape, 14) // 14 = A0
              };

    binary_sensors:
      - id: binary_sensor_pin2
        name: Binary sensor pin 2
      - id: binary_sensor_pin3
        name: Binary sensor pin 3
        on_press:
          ...

The listed binary_sensors supports all options from Binary Sensor like automations and filters.

Sensor

Sensors allows for reading the analog value of an analog pin, those are from A0 to A7 except for A4 and A5. The value returned goes from 0 to 1023 (the value returned by the Arduino analogRead function).

Arduino analog inputs measures voltage. By default the sketch is configured to use the Arduino internal VREF comparer setup to 1 volt, so voltages bigger 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. To do so, pass an additional true value to the hub constructor:

auto ape_component = new ArduinoPortExpander(i2c_component, 0x08, true);

To setup sensors, create a custom platform as below, list in braces all the sensors you want, in the example below two sensors are declared on pin A1 and A2

Then declare the ESPHome reference of the sensor in the same order as declared in the lambda:

sensor:
  - platform: custom
    lambda: |-
      return {ape_analog_input(ape, 1),  // 1 = A1
              ape_analog_input(ape, 2)};
    sensors:
      - name: Analog A1
        id: analog_a1
        filters:
          - throttle: 1s
      - name: Analog A2
        id: analog_a2
        filters:
          - throttle: 2s

The listed sensors supports all options from Sensor like automations and filters.

Note

Sensors are polled by default every loop cycle so it is recommended to use the throttle filter to not flood the network.

Output

Arduinos binary outputs are supported in pins from 0 to 13.

To setup outputs, create a custom platform as below, list in braces all the outputs you want, in the example below two outputs are declared on pin 3 and 4

output:
- platform: custom
  type: binary
  lambda: |-
    return {ape_binary_output(ape, 3),
            ape_binary_output(ape, 4)};
  outputs:
    - id: output_pin_3
      inverted: true
    - id: output_pin_4
      inverted: true

switch:
  - platform: output
    name: Switch pin 3
    output: output_pin_3

light:
  - platform: binary
    name: Switch pin 4
    output: output_pin_4

Full Example

Let’s connect a 4 channel relay board and 2 push buttons to toggle the relays, a PIR sensor, a window and a door a LM35 temperature sensor and a voltage sensor. Seems a bit too much for an ESP8266? You’ll still have some spares I/Os.

esphome:
  name: test_arduino
  includes:
    - arduino_port_expander.h

esp8266:
  board: nodemcu

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

api:

ota:

# define i2c device
# for an ESP8266 SDA is D2 and goes to Arduino's A4
#                SCL is D1 and goes to Arduino's A5
i2c:
  id: i2c_component

logger:
  level: DEBUG

# define the port expander hub, here we define one with id 'expander1',
# but you can define many
custom_component:
  - id: expander1
    lambda: |-
      auto expander = new ArduinoPortExpander(i2c_component, 0x08, true);
      return {expander};

# define binary outputs, here we have 4, as the relays are inverse logic
# (a path to ground turns the relay ON), we defined the inverted: true
# option of ESPHome outputs.
output:
- platform: custom
  type: binary
  lambda: |-
    return {ape_binary_output(expander1, 2),
            ape_binary_output(expander1, 3),
            ape_binary_output(expander1, 4),
            ape_binary_output(expander1, 5)};

  outputs:
    - id: relay_1
      inverted: true
    - id: relay_2
      inverted: true
    - id: relay_3
      inverted: true
    - id: relay_4
      inverted: true

# connect lights to the first 2 relays
light:
  - platform: binary
    id: ceiling_light
    name: Ceiling light
    output: relay_1
  - platform: binary
    id: room_light
    name: Living room light
    output: relay_2

# connect a fan to the third relay
fan:
- platform: binary
  id: ceiling_fan
  output: relay_3
  name: Ceiling fan

# connect a pump to the 4th relay
switch:
  - platform: output
    name: Tank pump
    id: tank_pump
    output: relay_4


# define binary sensors, use the Arduino PIN number for digital pins and
# for analog use 14 for A0, 15 for A1 and so on...
binary_sensor:
  - platform: custom
    lambda: |-
      return {ape_binary_sensor(expander1, 7),
              ape_binary_sensor(expander1, 8),
              ape_binary_sensor(expander1, 9),
              ape_binary_sensor(expander1, 10),
              ape_binary_sensor(expander1, 14) // 14 = A0
              };

    binary_sensors:
      - id: push_button1
        internal: true # don't show on HA
        on_press:
          - light.toggle: ceiling_light
      - id: push_button2
        internal: true # don't show on HA
        on_press:
          - light.toggle: room_light
      - id: pir_sensor
        name: Living PIR
        device_class: motion
      - id: window_reed_switch
        name: Living Window
        device_class: window
      - id: garage_door
        name: Garage garage
        device_class: garage_door

# define analog sensors
sensor:
  - platform: custom
    lambda: |-
      return {ape_analog_input(expander1, 1),  // 1 = A1
              ape_analog_input(expander1, 2)};
    sensors:
      - name: LM35 Living room temperature
        id: lm35_temp
        filters:
          # update every 60s
          - throttle: 60s
          # LM35 outputs 0.01v per ºC, and 1023 means 3.3 volts
          - lambda: return x * 330.0 / 1023.0;
      - name: Analog A2
        id: analog_a2
        filters:
          - throttle: 2s

See Also

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