Interfacing via I2C

We have an example, minimal I2C-based component here.

Let's take a closer look at this example.

Python

In addition to the usual requisite imports, we have:

from esphome.components import i2c

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

DEPENDENCIES = ["i2c"]

Given that this component will use--and consequently depend on--I2C, we must add it as a dependency. This allows ESPHome to understand this requirement and generate an error if it is not met.

empty_i2c_component_ns = cg.esphome_ns.namespace("empty_i2c_component")
EmptyI2CComponent = empty_i2c_component_ns.class_(
    "EmptyI2CComponent", cg.Component, i2c.I2CDevice
)

This is some boilerplate code which allows ESPHome code generation to understand the namespace and class names that the component will use. Note that EmptyI2CComponent is inheriting from both Component and I2CDevice.

CONFIG_SCHEMA = ...

This defines the configuration schema for the component as discussed here. In particular, note that the schema is extended with .extend(i2c.i2c_device_schema(0x01)) since this is an I2C component/platform. The 0x01 value is the default I2C address for the device to be used by this component/platform.

Finally, in the to_code function, we have:

await i2c.register_i2c_device(var, config)

Since this is an I2C device, we must register it as such so it is handled appropriately by ESPHome.

C++

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

class EmptyI2CComponent : public i2c::I2CDevice, public Component { ... };

As mentioned here, all components/platforms must inherit from either Component or PollingComponent; our example here is no different. Note that, since it's an I2C device, it also inherits from I2CDevice.

Finally, the component implements the usual set of methods as described here. This is all that's required for our minimal I2C component!