Push Button (Toggle)

In this very simple example, a push button is connected to a microcontroller. When the push button is pressed, it sends a message to Home Assistant, enabling you to physically control any other device.

The type of push button you are creating here acts like a toggle button: it does not preserve any state and has no distinct on and off state. Instead, it simply sends a signal when it is pressed and can be used to toggle devices.

Use Case

This example serves as a prototype for automating my lab: I want to build a physical dashboard with ten push buttons that controls ten “smart” plugs. This way, I can easily control devices in my lab (i.e. 3D printer, oscilloscope, bench supply, etc) from one simple-to-use physical control panel.

• This approach is much more versatile and also cheaper than mechanical plug bars with individual physical switches. In addition, I can separate locations for the switch board and for the actual plugs, eliminating the need to route AC cables back and forth through my lab.
• Another benefit is that one plug can be controlled by any number of buttons. This way, I can have a “main” dashboard plus also single buttons close to certain devices. For example, I want my 3D printer to be controllable both from my main dashboard and via a button right next to the printer (the built-in switch in the printer is located at its back side which is not easily accessible).
• Button functionality is also fully adjustable. The button right next to the 3D printer is going to turn on both the printer and the filament dryer.

Implementation

For this example, I am using a ESP32 DevKitC V4 board on an expansion board for easy prototyping, and the push button is connected to GPIO4. You can of course adapt this to just about any microcontroller board and any GPIO.

2 Steps

The implementation of an ESPHome device always consists of these two steps:

• Hardware Schematics: design the hardware circuitry (just as you would in conventional programming projects)
• Translate Hardware To Configuration: rather than programming the firmware yourself, you describe your hardware in the ESPHome device configuration.

Hardware Schematics

Here is the hardware schematic for this very simple project:

• When the user presses the push button, GPIO4 is pulled low.
• When the user releases the button, the pin is floating. So the pin needs to be configured as input and pullup (activating the ESP32 internal pullup resistor to keep the pin high when the button is not pressed).

Thanks to the expansion board that I use, and its dedicated GND pins for every GPIO, wiring is extremely simple:

Caveat: Pin Offset

When using an expansion board, be aware of possible pin offsets. Take a look at this setup:

The pin labels on the development board do not necessarily match the pin labels on the expansion board:

In the depicted case, the GPIO4 label on the development board aligns with the P0 label on the expansion board. The pin connected to GPIO4 (labeled P4) is slightly offset to the right.

When using expansion boards, always comply with the labels printed on the expansion board.

Translate To Configuration

In more conventional IDEs like Arduino IDE or platformio, you would now open the code editor and start manually programming the firmware.

In ESPHome, you describe your hardware details and requirements by as adding lines to the end of your existing default configuration.

I am assuming you already provisioned your microcontroller in ESPHome.

Do not replace your default configuration altogether with the code below! Just append the hardware information to the default configuration.

Fundamental Wiring

The fundamental wiring translates to this:

binary_sensor:
  - platform: gpio
    pin: GPIO4
    name: Pushbutton1

Edit your configuration right inside the web editor. This way, you get invaluable tooltips and IntelliSense-like auto-completion. Press Ctrl + Space to re-open Intellisense-dialogs if you accidentally closed them.

Component binary_sensor

A binary_sensor describes a component that can have exactly two states. The details (i.e. the GPIO the component is connected to) are specified as indented properties:

• platform: always GPIO
• pin: the pin number you are using
• name: the name you want to assign to this entity. This will be the name that you can later use in HomeAssistant to access the push button.

However, I haven’t yet completely described my requirements. The pin needs to be an input, and it should use a pullup resistor.

Fine-Tuning ESPHome Component

There are a few more things that need to be added to the configuration to adequately describe the hardware and its requirements:

• Input: The GPIO should act as an input because it reads the state of the connected push button.
• Pullup Resistor: The GPIO needs to activate its pullup resistor (so the GPIO is not in floating (undefined) state when the button is not pressed)
• Debouncing: We need debouncing because mechanical switches tend to vibrate and can produce unwanted high-frequency signals
• Exchange High And Low: According to the schematics, the button is connected to GND, so the GPIO is high when the button is not pressed, and it is low when the button is pressed. We need to invert this because we want some action to occur when the button is pressed, so it should be high when it is active, not vice versa.

All of this can be surprisingly easily accomplished. ESPHome components like binary_sensor are one-stop solutions that contain all the functionality typically needed.

You don’t need to write a single line of code to meet both of the above requirements. Just add these lines:

binary_sensor:
  - platform: gpio
    name: Pushbutton1
    pin: 
        number: GPIO4
        inverted: true
        mode:
          input: true
          pullup: true
    filters: 
      - delayed_on: 10ms
      - delayed_off: 10ms

Here is what the additional lines do:

• mode: the mode determines whether the GPIO acts as input or output.
• pullup: activates the internal pullup resistor. When the pin has no contact, it is pulled high.
• delayed_on/delayed_off: a state change must occur for at least the specified amount of time, effectively debouncing the button.
• inverted: inverts the GPIO signal.

It is best to first focus on one ESPHome component only, i.e. the binary_sensor. Visit the documentation and the pin schema to find out what the component can do for you.

When you are done updating your configuration, click SAVE and then close the editor to return to the ESPHome Dashboard.

When closing the editor window without first clicking SAVE, you are losing all of your edits. There is no confirmation dialog.

Validate Configuration

Before you proceed, immediately after any edits go ahead and always validate your configuration.

This makes sure your updated configuration does not contain formal errors. Click the three-dot menu, and choose Validate.

If there are issues with your configuration, you get error messages similar to this:

mapping values are not allowed here
  in "/config/esphome/push-button.yaml", line 35, column 18

The most likely cause are wrong indentation, wrong keyword order, and missing hyphens.

Always review the ESPHome documentation for the component you are using to see which keywords belong to the same entity, and how they should be grouped.

Uploading New Firmware

Once validated, click the three dot menu on the ESPHome tile and click Install, then Wirelessly, to automatically build and upload the firmware for your updated configuration.

Once uploaded, click STOP to close the terminal window, then visit the ESPHome Dashboard and verify that your updated device is marked ONLINE.

Testing Device

Sometimes - as in this case - the device cannot be tested directly. When you press the button, there is no visible response.

To test and diagnose a device in Home Assistant, click Developer tools in the sidebar, then click the tab STATES.

If your sensor does not show up, you might have to add it to Home Assistant first. Check Notifications in the sidebar to see whether Home Assistant has auto-detected your device, and add it to Home Assistant.

Next, click the text box below Entity, and enter part of the name of your device. You can now see its entities:

The push button is represented by the entity binary_sensor.push_button_pushbutton1, and its State is off.

This is correct: the push button is not pressed, so the GPIO is pulled high, and since the configuration added inverted:true, the current state is low.

Once you press the push button, the value of State should immediately change from false to true. If it does not, you need to review your wiring and your configuration and make sure both match, and you specified the correct GPIO pin.

What’s Next?

You now have a fully functional wireless toggle button, however it does not do anything useful. After all, your device just has a toggle button, but there is nothing on your device that could be controlled by the button.

That’s by design - and a key difference to classic programming where devices are always stand-alone and must implement everything by themselves.

In this case, though, you created an ESPHome device which is designed to be added to Home Assistant and become just one of many devices. In the following articles you’ll see all remaining steps:

• Adding To Home Assistant: By adding your device to Home Assistant, it can control any other device.
• Adding Automation: By adding an automation, you teach Home Assistant what it should automatically do whenever you press the button.

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