Dual-GPIO ESPHome Configuration for Powerstrip

The previously discussed simple ESPHome configuration works perfectly well to switch on and off relais, and work as a smart powerstrip. You could even connect a simple LED to signal socket state.

Highly Flexible PowerStrip Controller

In this article, I’ll add some rather minor changes to the previous configuration. These changes create a highly flexible powerstrip controller that can be used with all types of relais, and supports simple as well as the most sophisticated signal LEDs.

The new configuration below uses two GPIOs per switch that work complementary to each other (so when one GPIO is high, then the other one is low). That’s all the magic that is required to provide you with a highly functional microcontroller at the heart of smart powerstrips:

• Active Low And Active High Relais: there are two different relay board types available: active high turn the relais on when the trigger pin is high, whereas active low does the opposite. Since this configuration provides both an active high and an active low GPIO, it is at your discretion what type of relais you want to useand whether you want the relais to be on or off when the switch is on. Simply connect the relais trigger pin to the appropriate GPIO.
• Signal LED: with two complimentary switched GPIOs, both capable of sourcing and sinking current, you have virtually all options available to hook up any type of signal LEDs (just make sure you always use a current limiting resistor as you would normally do): for example, connect a simple LED to one GPIO and GND to indicate on or off state. Or, connect two simple LEDs in reverse order to each other in order to have one LED signal on state and the other LED signal off state. You can even connect a bi-polar bi-color status LED directly across both GPIOs (while still using a current limiting resistor in series), and have this one bi-color LED change colors based on switch state. If you use a three-legged bi-color LED or a four-legged RGB LED, connect the common cathode to GND/the common anode to positive supply voltage, and connect either leg to one of the GPIOs.

Picking Microcontroller

I picked a ESP32-C3 Super Mini microcontroller for this project. I chose this microcontroller because…

• Size: it has a very small foot print, and since I want to squeeze it into a commercial powerstrip, a small size matters
• GPIO: five switches require ten GPIOs, and this microcontroller has ten freely usable GPIOs
• Five Switches: implementing five switches seems like a reasonable trade-off as it supports 2-, 3-, 4-, and 5-socket powerstrips, and may even provide a spare switch to use with 4-socket powerstrips that have a built-in USB power supply.

Using Different Microcontroller

If you don’t have a ESP32-C3 Super Mini at hand, you can of course use any other microcontroller that is supported by ESPHome.

If you do use a different microcontroller, make sure you change the microcontroller type in your configuration, and adjust the assigned GPIO numbers to those available with the microcontroller you picked.

If your microcontroller has less than ten available GPIOs, simply reduce the number of switches, and if it has more, you can add more switches.

ESP32-C3 Super Mini

Here is the initial part of the ESPHome configuration for a ESP32-C3 Super Mini:

esphome:
  name: c3-supermini-test
  friendly_name: C3 SuperMini Test
  platformio_options:
    board_build.f_flash: 40000000L
    board_build.flash_mode: dio
    board_build.flash_size: 4MB

esp32:
  board: esp32-c3-devkitm-1
  variant: esp32c3
  framework:
    type: arduino

Assigned Pins

The switches defined in this configuration will use all ten freely usable GPIOs available with the ESP32-C3 Super Mini:

GPIO High is the GPIO that goes high when the switch is on (high active). GPIO Low is the GPIO that goes low when the same switch is on (low active).

If you pick a different microcontroller type, make sure you change the GPIO numbers and use the GPIO numbers that are freely available with the microcontroller you picked.

Defining Switches

The microcontroller needs to implement five switches. Each switch controls two GPIOs and switches them complimentary to each other. So when one GPIO is high, then the other GPIO is low, and vice versa.

Here is what the configuration is defining to implement this behavior:

• Status LED: (optional) light: defines a status led and uses the built-in LED on the microcontroller board (pin 8 with the ESP32-C3 Super Mini, inverted = low active). This LED will later signal connectivity status and can also be manually turned on and off for diagnosis. If you pick a different microcontroller, change pin 8 to whatever pin is wired to the built-in LED on your board. Remove inverted: true if the LED on your board is high active. If your board has no built-in LED, or if you don’t want a status LED, remove the section.
• Output Pins: output: defines the output pins (GPIOs). Note that there is always an inverted GPIO (inverted: true), and a normal GPIO per switch.
• Switches: switch: defines the switches. Per switch, it defines the primary GPIO (using output:), plus it defines events (on_turn_on:, on_turn_off:) to define the secondary GPIO. It uses restore_mode: RESTORE_DEFAULT_OFF to remember switch state, and if no saved state is available, the switch is turned off by default.

light:
  - platform: status_led
    name: "Status LED"
    id: esp_status_led
    icon: "mdi:alarm-light"
    pin:
      number: GPIO8
      inverted: true
    restore_mode: ALWAYS_OFF

output:
  - platform: gpio
    pin: GPIO0
    id: 'relay1'
    inverted: true
  - platform: gpio
    pin: GPIO2
    id: 'led1'
  - platform: gpio
    pin: GPIO3
    id: 'relay2'
    inverted: true
  - platform: gpio
    pin: GPIO4
    id: 'led2'
  - platform: gpio
    pin: GPIO21
    id: 'relay3'
    inverted: true
  - platform: gpio
    pin: GPIO20
    id: 'led3'
  - platform: gpio
    pin: GPIO10
    id: 'relay4'
    inverted: true
  - platform: gpio
    pin: GPIO7
    id: 'led4'
  - platform: gpio
    pin: GPIO6
    id: 'relay5'
    inverted: true
  - platform: gpio
    pin: GPIO5
    id: 'led5'
  
switch:
  - platform: output
    name: "Switch1"
    icon: "mdi:power-socket-eu"
    restore_mode: RESTORE_DEFAULT_OFF
    output: relay1
    on_turn_on:
      then: 
        - output.turn_on: led1
    on_turn_off:
      then:
        - output.turn_off: led1

  - platform: output
    name: "Switch2"
    icon: "mdi:power-socket-eu"
    restore_mode: RESTORE_DEFAULT_OFF
    output: relay2
    on_turn_on:
      then: 
        - output.turn_on: led2
    on_turn_off:
      then:
        - output.turn_off: led2
  
  - platform: output
    name: "Switch3"
    icon: "mdi:power-socket-eu"
    restore_mode: RESTORE_DEFAULT_OFF
    output: relay3
    on_turn_on:
      then: 
        - output.turn_on: led3
    on_turn_off:
      then:
        - output.turn_off: led3

  - platform: output
    name: "Switch4"
    icon: "mdi:power-socket-eu"
    restore_mode: RESTORE_DEFAULT_OFF
    output: relay4
    on_turn_on:
      then: 
        - output.turn_on: led4
    on_turn_off:
      then:
        - output.turn_off: led4

  - platform: output
    name: "Switch5"
    icon: "mdi:power-socket-eu"
    restore_mode: RESTORE_DEFAULT_OFF
    output: relay5
    on_turn_on:
      then: 
        - output.turn_on: led5
    on_turn_off:
      then:
        - output.turn_off: led5

It would be so much easier if ESPHome allowed output: to have more than one value, or to allow more than one output:. However, as of now this is not the case. That is why the configuration resorts to using the mentioned events in order to address an additional GPIO. I am sure there are many other workarounds to achieve the same, and maybe you feel inclined to leave a comment with your favorite solution.

Test Driving Microcontroller

Do not connect any components to your microcontroller yet. First, test the configuration on a naked microcontroller. So go ahead and install the configuration to your microcontroller.

1. Connect the microcontroller via USB to the computer running ESPHome (i.e. a Raspberry Pi), then install the configuration. Once the new firmware is uploaded and the microcontroller has rebooted, Home Assistant auto-detects your new device and notifies you in its sidebar.

   

2. Click CONFIGURE, and in the next dialog, click SUBMIT.

   

3. You can then assign a location to the device. When done, click FINISH. The microcontroller is now added to Home Assistant.

   

4. Now is the time to go and grab a coffee. Give Home Assistant a few minutes to fully import your new ESPHome device. If you continue right away, the device (and its entities like the switches) may not be ready yet, so they might be still missing, or are incomplete. It takes a few minutes for the import to be fully completed.

   

5. To verify that the configuration worked (and after you waited a few minutes), in the Home Assistant side bar, click Settings, then Devices&Services, then on the top of the window, click the tab Devices. Enter the name of your device (the name you used in the configuration). Double-click the device.

   

6. You now see the device details. In Device info, you see the microcontroller type you used. Controls lists the controls your microcontroller implements. This should be the Status LED, plus five switches. And Logbook shows the history: it logs when you turn switches on and off.

The section Controls will be used next to actually test-drive your microcontroller. If this section does not look like in the image above, and you are not seeing one Status LED and five switches, then you may have to wait a few minutes for Home Assistant to fully import your new device. If controls are still missing after waiting, carefully review your configuration and all the steps taken, and look for error messages you may have overlooked.

Testing Switches

You are now ready to test your microcontrollers’ functionality.

Testing Status LED

Start with a simple test, and toggle the Status LED. This should switch the blue on-board LED on the microcontroller board on and off. At the same time, whenever you change the state of one of the controls, the section Logbook records your action.

Testing Switch

Once this works, switch on the switch labeled Switch 3. This switch uses pins 20 and 21 which are conveniently located at one of the microcontrollers’ edges:

Connect a multimeter to these two pins, and set it to a voltage range of at least 5V. The multimeter should now show the supply voltage (i.e. 3.3V). When you turn off the switch, the multimeter still shows the supply voltage, but with reversed polarity (i.e. -3.3V).

Additional tests:

• Connect one lead of the multimeter to pin 20, and the other one to GND. You now get either supply voltage or 0V, based on switch state.
• Connect one lead of the multimeter to pin 21, and the other one to GND. You now again get either supply voltage or 0V, based on switch state - but this time in reversed order compared to the other pin.
• Connect a bi-polar bi-color LED to pin 20 (if you have one at hand). Connect a 330R current limiting resistor to the other LED leg, and connect the other end of the resistor to pin 21 (effectively powering the LED from both pins). The led should change color, based on switch state (because across both pins, there is always supply voltage, but with reversed polarity based on switch state).

Next Steps

Once you tested the configuration, and all works fine, you can now connect your relais trigger line to one of the two GPIOs per switch.

Which GPIO you choose depends on the type of relais logic, and how you want the relais to behave. With a low active relais, connect it to the GPIO Low pin (see the table above for the pin assignments).

If you’d like the relais to be off when the switch is on, or if you are using a high active relais, take the other GPIO.

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