RMT channels on ESP32

esp32_rmt_led_strip, remote_transmitter and remote_receiver each create one RMT channel, and all of them share the chip’s few RMT channels and their memory. ESPHome checks them together, so a config where one of them would fail at boot with no free tx channels is caught before it is flashed. A component that creates its own RMT channel with the ESP-IDF rmt_new_tx_channel() or rmt_new_rx_channel() joins this check with three helpers from esp32_rmt:

• esp32_rmt.request_rmt_channel(direction, setup_priority): add it at the end of CONFIG_SCHEMA, after the schema has filled in the defaults. direction is "TX" or "RX". setup_priority is the value your C++ get_setup_priority() returns, since the channel is created in setup(); an entry’s own setup_priority overrides it. It checks rmt_symbols against what ESP-IDF accepts and records the channel.
• esp32_rmt.final_validate_rmt_channels(config): call it from FINAL_VALIDATE_SCHEMA. It fails validation when the components need more channels than the chip has, or when more than one of them sets use_dma in one direction.
• esp32_rmt.register_rmt_channel(config): call it in to_code right after cg.register_component(). It records the order the components are registered in, which decides the order they are set up in. During code generation ESPHome then allocates the RMT memory in that order like ESP-IDF does, and logs a warning with a suggested rmt_symbols when a channel will not fit.

The entry needs an id and an rmt_symbols value on every variant with RMT; use_dma and name are optional and used when present. Use all three helpers: a component that leaves one out is only partly checked.

from esphome.components import esp32_rmt

CONFIG_SCHEMA = (
    cv.Schema(
        {
            cv.GenerateID(): cv.declare_id(MyComponent),
            cv.Optional(CONF_RMT_SYMBOLS, default=64): cv.int_,
            cv.Optional(CONF_USE_DMA): cv.boolean,
        }
    )
    .extend(cv.COMPONENT_SCHEMA)
    # setup_priority::HARDWARE, from MyComponent::get_setup_priority()
    .add_extra(esp32_rmt.request_rmt_channel("TX", 800.0))
)

FINAL_VALIDATE_SCHEMA = esp32_rmt.final_validate_rmt_channels


async def to_code(config):
    var = cg.new_Pvariable(config[CONF_ID])
    cg.add(var.set_rmt_symbols(config[CONF_RMT_SYMBOLS]))
    cg.add_optional(var.set_with_dma, config.get(CONF_USE_DMA))
    await cg.register_component(var, config)
    esp32_rmt.register_rmt_channel(config)

A component with its own final validation calls esp32_rmt.final_validate_rmt_channels(config) from it instead.

The combined checks are skipped in --testing-mode, where component test grouping merges the RMT components of many test configs into one build.

On variants without RMT (esp32_rmt.VARIANTS_NO_RMT), reject the RMT-only keys by adding .add_extra(esp32_rmt.validate_rmt_not_supported([CONF_RMT_SYMBOLS, CONF_USE_DMA])) to CONFIG_SCHEMA.