no_std Datasets

Four dataset types are available without the standard library.

Param<T>

Read-only parameter values. Works identically in no_std and std. Requires T: Clone + Serialize.

let threshold = Param(500u16);

See Param.

CellDataset<T>

Stack-friendly intermediate storage using Cell. Requires T: Copy.

let reading = CellDataset::<u16>::new();
let result = CellDataset::<bool>::new();

• const fn new() — usable in static contexts
• No heap allocation, no locking
• Single-threaded only (SequentialRunner)

See Cell Dataset.

RegisterDataset<T>

Volatile memory-mapped register access. Reads and writes at a raw memory address using read_volatile / write_volatile.

// SAFETY: address must point to a valid, aligned register
static SENSOR: RegisterDataset<u16> = unsafe { RegisterDataset::new(0x4000_0000) };

• T is typically u8, u16, or u32
• const unsafe fn new(address: usize) — suitable for static declarations
• load() reads the register, save() writes it

GpioDataset

A single GPIO pin within a memory-mapped register. Reads and writes a single bit at a given position.

// SAFETY: address must point to a valid GPIO port register
static LED: GpioDataset = unsafe { GpioDataset::new(0x4002_0000, 5, "LED1") };

• load() returns bool — whether the bit is set
• save(true) sets the bit, save(false) clears it
• Preserves other bits in the register (read-modify-write)
• The label field is used in visualization

Hardware dataset safety

Both RegisterDataset and GpioDataset use unsafe constructors because they access raw memory addresses. They implement Send + Sync via unsafe impls — this is safe in single-threaded embedded contexts but the caller is responsible for preventing data races in multi-threaded environments.

Example: embedded pipeline

struct Catalog {
    sensor: RegisterDataset<u16>,
    reading: CellDataset<u16>,
    alert: GpioDataset,
}

struct Params {
    threshold: Param<u16>,
}

fn pipeline<'a>(cat: &'a Catalog, params: &'a Params) -> impl Steps<PondError> + 'a {
    (
        Node {
            name: "read",
            func: |raw: u16| (raw,),
            input: (&cat.sensor,),
            output: (&cat.reading,),
        },
        Node {
            name: "check",
            func: |value: u16, thresh: u16| (value > thresh,),
            input: (&cat.reading, &params.threshold),
            output: (&cat.alert,),
        },
    )
}