Pipeline file

The pipeline file says what a node does with its hardware: which devices produce readings, what happens to those readings, and what a cell can see and change. It names devices, not pins, so the same pipeline runs against any board whose devices match.

pipeline:
  id: basic-sensors

sources: []
steps: []
taps: []
outlets: []

Only pipeline.id is required. The four lists all default to empty.

sources

Binds a device from the board file and runs it.

Key	Required	Meaning
id	yes	Name used to refer to this source's readings
device	yes	A device id from the board file
config	no	Settings the driver declared as scope: application

sample_interval_ms is accepted in config on every sensor source. It is not part of the driver's own configuration: the pipeline uses it to set the loop rate. When it is omitted, the driver's descriptor default applies, which differs per device.

steps

Transforms a value on its way through.

Key	Required	Meaning
id	yes	Name used to refer to this step's output
op	yes	Which step module, from the steps reference
input	yes	What feeds it
config	no	Settings the step declared

A step has exactly one input. Several steps may share one input, so a value can fan out.

taps

Publishes a value under a name a cell can resolve.

Key	Required	Meaning
name	yes	The name a cell resolves
kind	yes	retained or event
type	yes	The declared payload type
source	yes	What produces the value

retained holds the latest value with a timestamp and reading does not consume it. event is a queue the reader drains, and carries no timestamp.

A third kind, batch, is reserved for planned work. Declaring one fails generation with batch taps not yet supported by codegen.

outlets

Exposes a value a cell, or a step, can write.

Key	Required	Meaning
name	yes	The name a cell resolves
type	yes	The value type the driver accepts
device	yes	A device id from the board file
input	no	A step whose output drives this outlet with no cell involved
config	no	Settings for the outlet

write_interval_ms in config sets how often the device's task applies the latest value. It defaults to 100 ms and must be at least 1.

A device may be driven by exactly one outlet.

What can be referenced

Wherever a source: or an input: is expected, one of these forms is accepted:

Form	Refers to
<source id>.<output name>	one of a driver's published outputs
<step id>	the output of a step
<outlet name>.<status field>	a read-back from a device that reports its state
<outlet name>.error	faults from that outlet, as OutletFault

Payload types

These are the type names accepted in a tap's or outlet's type field.

Type	Used for
f32, f64	measurements
u8, u16, u32, u64, usize	counts and raw values
i32, i64	signed values
bool	on/off state, such as a contact read-back
DigitalState	value for an on/off output
PwmDuty	value for a duty-cycle output
ThresholdAlarm	event from a threshold step
OutletFault	event from an outlet's .error
HealthEvent, DriverHealth	source health, on _signal_layer_health

A tap's declared type is checked twice: against what produces it during generation, and against what a cell asks for at runtime. The typed SDK calls compare their type with the declared one before decoding and fail with a type-mismatch error; payloads are decoded strictly, refusing trailing bytes. Only the raw byte reads and writes bypass the cell-side check.

Limits

Limit	Value
Taps per pipeline	16, of which 1 is reserved for _signal_layer_health when the pipeline has any source
Outlets per pipeline	8
Events held per event tap	8, oldest dropped when full

Reserved names

Names beginning with _ are reserved for taps the generator injects. Today that is _signal_layer_health, added automatically to any pipeline with at least one source.