Embedded Abstractions

# Embedded Abstractions

## A Generic Peripheral Abstraction

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## The Full Rust "no-std" Stack

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## Micro Architecture Crate

Provides low-level access to CPU-specific features: interrupt handling, system timer, core registers. For RISC-V (ESP32-C3), this is the `riscv` crate.

Not something you interact with directly in most application code, but it's the foundation everything else builds on.

```rust
// Example: enabling interrupts at the CPU level
unsafe { riscv::interrupt::enable() };
```

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## The Peripheral Access Crate

Auto-generated from SVD files. A Rust representation of every register in the chip. Type-safe but low-level. You *can* use it directly, but you almost never need to.

For ESP32-C3: the `esp32c3` crate.

```rust
// PAC-level: writing directly to a register
peripherals.GPIO.out_w1ts
    .write(|w| unsafe { w.bits(1 << 5) });
```

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## The Hardware Abstraction Layer

Safe, ergonomic Rust APIs on top of the PAC. This is where we'll spend most of our time. For ESP32 chips: `esp-hal`.

Provides the Instantiate → Configure → Control pattern for every peripheral.

```rust
// HAL-level: safe, readable, type-checked
let mut led = Output::new(
    peripherals.GPIO5,
    Level::Low,
    OutputConfig::default(),
);
led.set_high();
```

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## embedded-hal Traits

The key to portability. These traits define a standard interface that any HAL can implement.

This is the contract between HALs and driver crates.

```rust
// Works on ANY microcontroller
fn blink(
    pin: &mut impl OutputPin,
    delay: &mut impl DelayNs,
) {
    pin.set_high().unwrap();
    delay.delay_ms(500);
    pin.set_low().unwrap();
    delay.delay_ms(500);
}
```

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## Driver Crates

Built on top of `embedded-hal` traits. A driver crate provides a high-level API for a specific sensor or device. Ideally drivers would all use `embedded-hal` traits but they don't need to. A driver that does use the traits though, is what makes it hardware-agnostic.

```rust
// This driver doesn't know about ESP32.
// It just needs something that implements I2c.
let mut imu = Icm42670::new(
    i2c, Address::Primary,
);
let accel = imu.accel_norm().unwrap();
```

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## Board Support Packages

The highest layer. Pre-configures everything for a specific board: pin assignments, peripheral setup, default configurations. Instead of remembering pin numbers, you use meaningful names.

```rust
// Without BSP:
let led = Output::new(
    peripherals.GPIO5,
    Level::Low,
    OutputConfig::default(),
);

// With BSP: the board knows
let led = board.led();
```

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The Embedded Rustacean · Rust Week 2026