hal::pio

Programmed digital I/O, not an addressed bus. Backends lower this small, portable instruction set; applications never provide native opcodes. This initial contract has one board-routed input and one output, explicit 32-bit FIFOs, and no interrupt, DMA, side-set or arbitrary instruction access.

Structs

Config

struct Config {
    pub frequency_hz: u32,
    pub input: bool,
    pub output: bool,
}

Implements: Clone, Copy, Debug, Eq, PartialEq, StructuralPartialEq

Instruction

struct Instruction {
    pub operation: Operation,
    pub delay: u8,
}

Implements: Clone, Copy, Debug, Eq, PartialEq, StructuralPartialEq

References: Operation

Enums

Error

enum Error {
    Busy,
    Invalid,
    NoSpace,
    NotConfigured,
    WouldBlock,
    Timeout,
    Hardware,
    Unsupported,
}

Implements: Clone, Copy, Debug, Eq, PartialEq, StructuralPartialEq

Operation

enum Operation {
    Pull,
    Push,
    OutputBit,
    InputBit,
    SetOutput(bool),
    WaitInput(bool),
    SetCounter(u8),
    Jump(u8),
    JumpDecrement(u8),
    Nop,
}

Implements: Clone, Copy, Debug, Eq, PartialEq, StructuralPartialEq

Traits

ProgrammableIo

trait ProgrammableIo: Send {
    fn configure(&mut self, machine: u8, program: &[Instruction], config: Config) -> Result<(), Error>
    fn start(&mut self, machine: u8) -> Result<(), Error>
    fn try_write(&mut self, machine: u8, word: u32) -> Result<(), Error>
    fn try_read(&mut self, machine: u8) -> Result<u32, Error>
    fn exchange(&mut self, machine: u8, word: u32, timeout_us: u32) -> Result<u32, Error>
    fn cancel(&mut self, machine: u8) -> Result<(), Error>
    fn reset(&mut self)
}

Exclusive owner of an engine and its board-routed pins. Machine indices are local to this owner, not globally transferable handles. Every method takes exclusive access; external synchronization belongs to the caller. Programs wrap from their last instruction to their first. Configure reserves program memory and a machine but leaves it stopped. Each routed pin can be used by only one configured machine, even for input.