PYTHON · NUMPY · IN-BROWSER

GPIO, Peripherals & the Control Loop

Write your first no_std Rust firmware: own the rover's peripherals, blink a GPIO LED, and drive the motors from the control loop to reach the goal.

01Challenge

The Bench opens on firmware whose control() only blinks the LED — the rover sits still. Press Compile & Run: it builds real Rust to WASM and the rover doesn't move. Your job: make this firmware drive to the green pad.

02Model

On the Python tier you called set_motor(...). What ran underneath? A control loop on a chip, talking to motor and sensor peripherals it OWNS. In Rust that ownership is literal: you take() the Peripherals once, as a value — the compiler then guarantees no two parts of your code fight over the same motor. The loop runs every tick like a heartbeat: read sensors, decide, drive. The same embodied loop you've known since the blocks tier — now you're writing the metal that runs it.

Firmware owns the board's peripherals.

03Guided practice

1. Take the peripherals. control_loop!(control) exports the tick; inside, p is your &mut Peripherals. 2. Read the goal beacon. p.goal.distance() (m) and p.goal.bearing() (rad, + = left). 3. Drive the motors. p.motors.set(left, right) in [-1, 1]. 4. Steer + go. let turn = 1.2 * bearing; then let forward = if dist > 0.2 { 0.6 } else { 0.0 }; and p.motors.set(forward - turn, forward + turn); 5. GPIO. Keep p.led.set(dist > 0.2).

04Feedback

PASS WHEN The firmware compiles as no_std and drives the rover within 0.2 m of the pad.

Closest approach barely changed — your motors are still set(0.0, 0.0). Compute turn from bearing and a forward term, then p.motors.set(forward - turn, forward + turn).
Rover spun/veered away — the steering sign is flipped. bearing is + when the goal is LEFT: set(forward - turn, forward + turn).
rustc error 'cannot find value `bearing`' — you read it into `_bearing`; drop the underscore to use it.

05Retrieve & space

Ownership: why does take() hand you the peripherals exactly once? (single guaranteed owner of each motor/pin).
Units: p.goal.bearing() is in ____ and + means the goal is to your ____ (radians; left).
What does control_loop!(control) generate? (a #[no_mangle] tick() the host calls each period).

06Mastery & project

Compile-and-run firmware (no_std, no emulator) that owns the peripherals and drives the rover into the pad.

Foundation of the metal capstone: every later firmware builds on this take → read → drive loop.

← Imitation and Sim-to-Real Timers, PWM & Proportional Drive →

! { loop {} }\nuse physical_ai_hal::*;\n\n// control() runs every control period (like a timer interrupt). Right now it\n// only blinks the LED — the rover never moves. Make it drive to the goal pad.\nfn control(p: &mut Peripherals) {\n let dist = p.goal.distance(); // metres to the goal\n let _bearing = p.goal.bearing(); // radians, + = goal is to your LEFT\n p.led.set(dist > 0.2); // GPIO: status LED on while still driving\n\n // TODO: steer toward the goal (use _bearing) and drive forward.\n p.motors.set(0.0, 0.0);\n}\ncontrol_loop!(control);\n","task":{"goal":[1.2,1.2],"time":12.0,"tol":0.2},"title":"GPIO, Peripherals & the Control Loop"}">

PYTHON · NUMPY · IN-BROWSER

GPIO, Peripherals & the Control Loop

Write no_std embedded Rust against the rover HAL. It compiles to WASM and runs as the real control loop.