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[WIP] PIO stepper 2-pin driver support #5690

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[WIP] PIO stepper 2-pin driver support #5690

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85a2ec8
refactor: move stepper to stepper4 and rename structs
GrbavaCigla Mar 19, 2026
a45b8ea
fix: rename missing from previous commit
GrbavaCigla Mar 19, 2026
1eda416
feat: add stepper2 wip implementation
GrbavaCigla Mar 19, 2026
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3 changes: 2 additions & 1 deletion embassy-rp/src/pio_programs/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ pub mod onewire;
pub mod pwm;
pub mod rotary_encoder;
pub mod spi;
pub mod stepper;
pub mod stepper4;
pub mod stepper2;
Comment on lines -11 to +12
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@CBJamo CBJamo Mar 26, 2026

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Bit of a nitpick, but I think these names need to be more descriptive. Perhaps Stepper4 -> StepperPhases and Stepper2 -> StepDir?

pub mod uart;
pub mod ws2812;
72 changes: 72 additions & 0 deletions embassy-rp/src/pio_programs/stepper2.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,72 @@
use core::f64::consts::PI;
use embassy_rp::{
Peri,
gpio::Output,
pio::{
Common, Config, Direction, Instance, LoadedProgram, PioPin, StateMachine,
program::pio_asm,
},
pio_programs::clock_divider::calculate_pio_clock_divider,
};

pub struct PioStepper2Program<'a, PIO: Instance> {
prg: LoadedProgram<'a, PIO>,
}

impl<'a, PIO: Instance> PioStepper2Program<'a, PIO> {
pub fn new(common: &mut Common<'a, PIO>) -> Self {
let prg = pio_asm!(
".wrap_target",
"pull block",
"out x, 32",
"loop:",
" set pins, 1 [31]",
" set pins, 0 [31]",
" jmp x-- loop",
".wrap"
);

let prg = common.load_program(&prg.program);

Self { prg }
}
}

pub struct Stepper2<'d, T: Instance, const SM: usize> {
sm: StateMachine<'d, T, SM>,
dir: Output<'d>,
}

impl<'d, T: Instance, const SM: usize> Stepper2<'d, T, SM> {
pub fn new(
pio: &mut Common<'d, T>,
mut sm: StateMachine<'d, T, SM>,
stp: Peri<'d, impl PioPin>,
dir: Output<'d>,
program: &PioStepperProgram<'d, T>,
) -> Self {
let stp = pio.make_pio_pin(stp);
sm.set_pin_dirs(Direction::Out, &[&stp]);

let mut cfg = Config::default();
cfg.set_set_pins(&[&stp]);

cfg.clock_divider =
calculate_pio_clock_divider(100 * 65);

cfg.use_program(&program.prg, &[]);
sm.set_config(&cfg);
sm.set_enable(true);
Self { sm, dir }
}

pub fn set_frequency(&mut self, freq: u32) {
let clock_divider = calculate_pio_clock_divider(freq * 65);
let divider_f32 = clock_divider.to_num::<f32>();
assert!(divider_f32 <= 65536.0, "clkdiv must be <= 65536");
assert!(divider_f32 >= 1.0, "clkdiv must be >= 1");

self.sm.set_clock_divider(clock_divider);
self.sm.clkdiv_restart();
}
}
10 changes: 5 additions & 5 deletions embassy-rp/src/pio_programs/stepper.rs → embassy-rp/src/pio_programs/stepper4.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,11 +7,11 @@ use crate::pio::{Common, Config, Direction, Instance, Irq, LoadedProgram, PioPin
use crate::pio_programs::clock_divider::calculate_pio_clock_divider;

/// This struct represents a Stepper driver program loaded into pio instruction memory.
pub struct PioStepperProgram<'a, PIO: Instance> {
pub struct PioStepper4Program<'a, PIO: Instance> {
prg: LoadedProgram<'a, PIO>,
}

impl<'a, PIO: Instance> PioStepperProgram<'a, PIO> {
impl<'a, PIO: Instance> PioStepper4Program<'a, PIO> {
/// Load the program into the given pio
pub fn new(common: &mut Common<'a, PIO>) -> Self {
let prg = pio::pio_asm!(
Expand All @@ -37,12 +37,12 @@ impl<'a, PIO: Instance> PioStepperProgram<'a, PIO> {
}

/// Pio backed Stepper driver
pub struct PioStepper<'d, T: Instance, const SM: usize> {
pub struct PioStepper4<'d, T: Instance, const SM: usize> {
irq: Irq<'d, T, SM>,
sm: StateMachine<'d, T, SM>,
}

impl<'d, T: Instance, const SM: usize> PioStepper<'d, T, SM> {
impl<'d, T: Instance, const SM: usize> PioStepper4<'d, T, SM> {
/// Configure a state machine to drive a stepper
pub fn new(
pio: &mut Common<'d, T>,
Expand All @@ -52,7 +52,7 @@ impl<'d, T: Instance, const SM: usize> PioStepper<'d, T, SM> {
pin1: Peri<'d, impl PioPin>,
pin2: Peri<'d, impl PioPin>,
pin3: Peri<'d, impl PioPin>,
program: &PioStepperProgram<'d, T>,
program: &PioStepper4Program<'d, T>,
) -> Self {
let pin0 = pio.make_pio_pin(pin0);
let pin1 = pio.make_pio_pin(pin1);
Expand Down
6 changes: 3 additions & 3 deletions examples/rp/src/bin/pio_stepper.rs
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Expand Up @@ -9,7 +9,7 @@ use embassy_executor::Spawner;
use embassy_rp::bind_interrupts;
use embassy_rp::peripherals::PIO0;
use embassy_rp::pio::{InterruptHandler, Pio};
use embassy_rp::pio_programs::stepper::{PioStepper, PioStepperProgram};
use embassy_rp::pio_programs::stepper::{PioStepper4, PioStepper4Program};
use embassy_time::{Duration, Timer, with_timeout};
use {defmt_rtt as _, panic_probe as _};

Expand All @@ -24,8 +24,8 @@ async fn main(_spawner: Spawner) {
mut common, irq0, sm0, ..
} = Pio::new(p.PIO0, Irqs);

let prg = PioStepperProgram::new(&mut common);
let mut stepper = PioStepper::new(&mut common, sm0, irq0, p.PIN_4, p.PIN_5, p.PIN_6, p.PIN_7, &prg);
let prg = PioStepper4Program::new(&mut common);
let mut stepper = PioStepper4::new(&mut common, sm0, irq0, p.PIN_4, p.PIN_5, p.PIN_6, p.PIN_7, &prg);
stepper.set_frequency(120);
loop {
info!("CW full steps");
Expand Down
6 changes: 3 additions & 3 deletions examples/rp235x/src/bin/pio_stepper.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ use embassy_executor::Spawner;
use embassy_rp::bind_interrupts;
use embassy_rp::peripherals::PIO0;
use embassy_rp::pio::{InterruptHandler, Pio};
use embassy_rp::pio_programs::stepper::{PioStepper, PioStepperProgram};
use embassy_rp::pio_programs::stepper::{PioStepper4, PioStepper4Program};
use embassy_time::{Duration, Timer, with_timeout};
use {defmt_rtt as _, panic_probe as _};

Expand All @@ -24,8 +24,8 @@ async fn main(_spawner: Spawner) {
mut common, irq0, sm0, ..
} = Pio::new(p.PIO0, Irqs);

let prg = PioStepperProgram::new(&mut common);
let mut stepper = PioStepper::new(&mut common, sm0, irq0, p.PIN_4, p.PIN_5, p.PIN_6, p.PIN_7, &prg);
let prg = PioStepper4Program::new(&mut common);
let mut stepper = PioStepper4::new(&mut common, sm0, irq0, p.PIN_4, p.PIN_5, p.PIN_6, p.PIN_7, &prg);
stepper.set_frequency(120);
loop {
info!("CW full steps");
Expand Down