Firmata can be used to add analog and digital inputs and outputs to Home Assistant. This allows for buttons, switches, motion detectors, relay control, sensors, potentiometers, dimmers, etc. The integration can currently connect to a Firmata board via serial or serial over USB.
The Firmata protocol is a standard protocol for microcontrollers. Most of these boards support digital and analog inputs and outputs. Arduino and Arduino-compatible microcontroller development boards are the most popular boards to use with Firmata.
There is currently support for the following device types within Home Assistant:
You will need to upload a Firmata firmware to your board. Please upload any
StandardFirmata sketch to your board; please refer to the Arduino documentation for further information for uploading sketches. Firmata is available in the Arduino Library Manager in the Arduino IDE. You may also use a Firmata Express.
To integrate Arduino boards with Home Assistant, add the following section to your
Firmata may cycle pins HIGH/LOW during initialization. If your pins should not be accidentally cycled, you may need to modify your Firmtata sketch or if you are using a relay board use an output pin as VCC. See this issue for details: Make initial pin value configurable.
You may configure multiple Firmata boards. Each board has the following options:
The port where your board is connected to your Home Assistant host. It is recommended to use the
by-id reference (instead of numerical like
/dev/ttyUSB0) since these will never change after a reboot. If you are using Home Assistant Operating System, you can find a list of connected serial devices in the Hardware dialog on the Settings > System > Hardware panel.
The baud rate of the Arduino sketch. If you are using Firmata Express, then you do not need to set this option. If you are using the default StandardFirmata, then you should set this to
If you are using Firmata Express, then this should match the instance number that you set in the sketch.
Time in seconds to wait for the Arduino is initially respond. May need to be used for boards that respond slowly at first connection.
Time in seconds to wait for reply from the Arduino after sending a command. Rarely needs to be adjusted.
Sampling interval in milliseconds sent to Firmata. Most Firmata sketches will ignore any interval less than 10 milliseconds.
Digital high/low outputs to configure
The digital or analog pin output mode. For switches, this must be set to
OUTPUT. No other output modes are currently implemented.
The initial output of the pin after initialization. Note that this is inverted if
negate is enabled.
PWM/Analog outputs to configure
The digital or analog pin number on the board. Note that most boards do not support analog or PWM output on all digital and analog pins.
The digital or analog pin output mode. For lights, this must be set to
PWM. No other output modes are currently implemented.
The initial output of the pin after initialization. This should be a Home Assistant-like value from 0 to 255; this value is then plugged into the
maximum scaling (if configured).
The minimum PWM/analog value to send (inclusive). This is the lowest allowed value that the pin will output. The Home Assistant brightness value (0 to 255) will be scaled with this value as the lower value of the range.
Digital or analog high/low input to configure
The digital or analog pin number on the board. For analog pins the corresponding digital number must be used. Please use the pinout that corresponds to your board. For example, on the Arduino Uno, pin A2 corresponds to the digital pin number 16.
The digital or analog pin input mode. Supported modes are
PULLUP. Check your board specifications to see which pins have optional internal pullups available.
Analog input to configure
The analog pin input mode. For sensors, this must be set to
ANALOG. No other input modes are currently implemented.
Minimum difference in value to update. The absolute value of the difference between the old and new value must be greater than or equal to this option for the update to register in Home Assistant. This is set to
40 by default to prevent an unconnected pin from clogging the Home Assistant history with updates. Set this to
1 to register all updates in Home Assistant. Updates are registered as fast as the board can send them (very fast). The minimum value that may be set is
To invert/negate a light, set the
0 and the
# Example firmata configuration.yaml entry firmata: - serial_port: /dev/serial/by-id/usb-Teensyduino_USB_Serial_358320-if00 serial_baud_rate: 57600 switches: - name: my_light pin_mode: OUTPUT pin: 4 negate: true - name: my_other_output pin_mode: OUTPUT pin: 5 initial: true - name: my_light2 pin_mode: OUTPUT pin: A6 initial: true negate: true lights: - name: my_dimmable_light pin_mode: PWM pin: 6 - name: my_subset_light pin_mode: PWM pin: 10 initial: 0 minimum: 127 maximum: 200 - name: my_inverted_light pin_mode: PWM pin: 11 minimum: 255 maximum: 0 binary_sensors: - name: my_motion pin_mode: INPUT pin: 2 - name: my_door pin_mode: PULLUP pin: 3 negate: true - name: my_other_door pin_mode: INPUT pin: 16 # A2 negate: true sensors: - name: my_sensor pin: A0 pin_mode: ANALOG differential: 40