Event Bus

The Event Bus is the backbone for system → app and app → system messaging within TheCube-Core.

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Topics

Events are organized by topic. Examples:

Topic pattern	Source	Description
system.presence	Core	mmWave presence state changes
system.network	Core	Network connectivity changes
system.power	Core	Power/battery events
hardware.gpio.interrupt	IO Bridge	GPIO pin interrupt events
hardware.uart.rx	IO Bridge	UART RX watermark events
hardware.uart.status	IO Bridge	UART line status changes
hardware.i2c.done	IO Bridge	I2C async transaction completions
hardware.spix.done	IO Bridge	SPI proxy transfer completions
hardware.pio.irq	IO Bridge	PIO interrupt events
hardware.fault	IO Bridge	Hardware fault (brownout, overtemp, flash error)
hardware.boot_reason	IO Bridge	Bridge reboot reason
ui.toast	Apps/Core	Toast notification requests
ui.banner	Apps/Core	Banner notification requests
audio.wake	Core	Wakeword detected
audio.stt.partial	Core	Partial STT transcript
audio.stt.final	Core	Final STT transcript
app.<id>.event.*	Apps	App-namespaced events

Envelope Format

{
    "topic": "system.presence",
    "ts": 1732212345,
    "source": "core",
    "priority": "normal",
    "payload": { "state": "present", "confidence": 0.94 }
}

QoS & Backpressure

• In-process pub/sub with bounded queues per subscriber.
• Backpressure drops low-priority events first (configurable per subscriber).
• High-priority events (PRIO flag from IO Bridge, fault events) are never dropped unless the queue is completely exhausted.
• Apps declare topic filters at registration; Core enforces quotas on subscription count and message rate.

Hardware Events

IO Bridge events are translated from the CubeBridge Protocol’s TLV format into standard Event Bus envelopes by the CORE. See API: Events for the complete list of hardware event types and their payloads.

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See Also

• API: Events — hardware and system event types
• Architecture — Event Bus in the system context
• Hardware: Expansion & IO Bridge — bridge event delivery model