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Interfacing via GPIO

We have an example, minimal component which uses a single GPIO pin here.

Let's take a closer look at this example.

Python

In addition to the usual requisite imports, we have:

from esphome import pins

This allows us to use some functions we'll need for validation and code generation later on.

empty_gpio_component_ns = cg.esphome_ns.namespace("empty_gpio_component")
EmptyGPIOComponent = empty_gpio_component_ns.class_("EmptyGPIOComponent", cg.Component)

This is some boilerplate code which allows ESPHome code generation to understand the namespace and class names that the component will use.

CONFIG_SCHEMA = ...

This defines the configuration schema for the component as discussed here. In particular, note that the schema includes cv.Required(CONF_PIN): pins.gpio_output_pin_schema,. Of note:

  • This specifically requires an output GPIO pin schema.
  • While a complete pin schema is permitted, it is often shortened to pin: GPIOXX.
  • This arrangement will allow any GPIO pin to be used -- including a GPIO pin which might be connected via an I/O expander! If you specifically require a pin that is "internal" to the microcontroller, you can use internal_gpio_output_pin_schema.
  • If you require an input pin, simply swap output for input in gpio_output_pin_schema.

Finally, in the to_code function, we have:

pin = await gpio_pin_expression(config[CONF_PIN])
cg.add(var.set_output_pin(pin))

This configures the component/platform to use the pin as specified in the YAML configuration.

C++

The C++ class for this example component is quite simple.

class EmptyGPIOComponent : public Component { ... };

As mentioned here, all components/platforms must inherit from either Component or PollingComponent; our example here is no different.

The void set_output_pin(GPIOPin *pin) method is implemented to allow setting the pin that the component should use.

Finally, the component implements the usual set of methods as described here. This is all that's required for our minimal GPIO component!