Skip to content

Commit

Permalink
Fix support for hardware PWM on Pi 5
Browse files Browse the repository at this point in the history
  • Loading branch information
@golemparts
golemparts committed May 17, 2024
1 parent 598e27a commit 6bbc5ef
Show file tree
Hide file tree
Showing 4 changed files with 151 additions and 90 deletions.
4 changes: 3 additions & 1 deletion CHANGELOG.md
View file
Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
# Changelog

## 0.17.2 (TBD)
## 0.18.0 (TBD)

* **Gpio**: Fix `InputPin` mode not getting set correctly for uninitialized (FUNCSEL 31 (NULL)) pins on Raspberry Pi 5 (contributed by @lukeburong).
* **Pwm**: (Breaking change) Add `Error::UnknownModel`.
* **Pwm**: Fix support for hardware PWM on Raspberry Pi 5, caused by incorrect PWM chip/channel.

## 0.17.1 (January 21, 2024)

Expand Down
102 changes: 55 additions & 47 deletions src/pwm.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -76,19 +76,33 @@ mod hal;
mod hal_unproven;
mod sysfs;

use crate::system::DeviceInfo;

const NANOS_PER_SEC: f64 = 1_000_000_000.0;

/// Errors that can occur when accessing the PWM peripheral.
#[derive(Debug)]
pub enum Error {
/// I/O error.
Io(io::Error),
/// Unknown model.
///
/// The Raspberry Pi model or SoC can't be identified. Support for
/// new models is usually added shortly after they are officially
/// announced and available to the public. Make sure you're using
/// the latest release of RPPAL.
///
/// You may also encounter this error if your Linux distribution
/// doesn't provide any of the common user-accessible system files
/// that are used to identify the model and SoC.
UnknownModel,
}

impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
Error::Io(ref err) => write!(f, "I/O error: {}", err),
Error::UnknownModel => write!(f, "Unknown Raspberry Pi model"),
}
}
}
Expand Down Expand Up @@ -152,7 +166,8 @@ impl fmt::Display for Polarity {
/// [here]: index.html
#[derive(Debug)]
pub struct Pwm {
channel: Channel,
chip: u8,
channel: u8,
reset_on_drop: bool,
}

Expand All @@ -164,9 +179,16 @@ impl Pwm {
///
/// [`enable`]: #method.enable
pub fn new(channel: Channel) -> Result<Pwm> {
sysfs::export(channel as u8)?;
// Select chip/channel based on Pi model
let device_info = DeviceInfo::new().map_err(|_| Error::UnknownModel)?;

let chip = device_info.pwm_chip();
let channel = device_info.pwm_channels()[channel as usize];

sysfs::export(chip, channel)?;

let pwm = Pwm {
chip,
channel,
reset_on_drop: true,
};
Expand Down Expand Up @@ -204,20 +226,10 @@ impl Pwm {
polarity: Polarity,
enabled: bool,
) -> Result<Pwm> {
sysfs::export(channel as u8)?;

let pwm = Pwm {
channel,
reset_on_drop: true,
};

// Always reset "enable" to 0. The sysfs pwm interface has a bug where a previous
// export may have left "enable" as 1 after unexporting. On the next export,
// "enable" is still set to 1, even though the channel isn't enabled.
let _ = pwm.disable();
let pwm = Pwm::new(channel)?;

// Set pulse width to 0 first in case the new period is shorter than the current pulse width
let _ = sysfs::set_pulse_width(channel as u8, 0);
let _ = sysfs::set_pulse_width(pwm.chip, pwm.channel, 0);

pwm.set_period(period)?;
pwm.set_pulse_width(pulse_width)?;
Expand Down Expand Up @@ -254,20 +266,10 @@ impl Pwm {
polarity: Polarity,
enabled: bool,
) -> Result<Pwm> {
sysfs::export(channel as u8)?;

let pwm = Pwm {
channel,
reset_on_drop: true,
};

// Always reset "enable" to 0. The sysfs pwm interface has a bug where a previous
// export may have left "enable" as 1 after unexporting. On the next export,
// "enable" is still set to 1, even though the channel isn't enabled.
let _ = pwm.disable();
let pwm = Pwm::new(channel)?;

// Set pulse width to 0 first in case the new period is shorter than the current pulse width
let _ = sysfs::set_pulse_width(channel as u8, 0);
let _ = sysfs::set_pulse_width(pwm.chip, pwm.channel, 0);

// Convert to nanoseconds
let period = if frequency == 0.0 {
Expand All @@ -277,8 +279,8 @@ impl Pwm {
};
let pulse_width = period * duty_cycle.clamp(0.0, 1.0);

sysfs::set_period(channel as u8, period as u64)?;
sysfs::set_pulse_width(channel as u8, pulse_width as u64)?;
sysfs::set_period(pwm.chip, pwm.channel, period as u64)?;
sysfs::set_pulse_width(pwm.chip, pwm.channel, pulse_width as u64)?;
pwm.set_polarity(polarity)?;
if enabled {
pwm.enable()?;
Expand All @@ -289,7 +291,10 @@ impl Pwm {

/// Returns the period.
pub fn period(&self) -> Result<Duration> {
Ok(Duration::from_nanos(sysfs::period(self.channel as u8)?))
Ok(Duration::from_nanos(sysfs::period(
self.chip,
self.channel,
)?))
}

/// Sets the period.
Expand All @@ -299,7 +304,8 @@ impl Pwm {
/// This method will fail if `period` is shorter than the current pulse width.
pub fn set_period(&self, period: Duration) -> Result<()> {
sysfs::set_period(
self.channel as u8,
self.chip,
self.channel,
u64::from(period.subsec_nanos())
.saturating_add(period.as_secs().saturating_mul(NANOS_PER_SEC as u64)),
)?;
Expand All @@ -310,7 +316,8 @@ impl Pwm {
/// Returns the pulse width.
pub fn pulse_width(&self) -> Result<Duration> {
Ok(Duration::from_nanos(sysfs::pulse_width(
self.channel as u8,
self.chip,
self.channel,
)?))
}

Expand All @@ -322,7 +329,8 @@ impl Pwm {
/// This method will fail if `pulse_width` is longer than the current period.
pub fn set_pulse_width(&self, pulse_width: Duration) -> Result<()> {
sysfs::set_pulse_width(
self.channel as u8,
self.chip,
self.channel,
u64::from(pulse_width.subsec_nanos())
.saturating_add(pulse_width.as_secs().saturating_mul(NANOS_PER_SEC as u64)),
)?;
Expand All @@ -335,7 +343,7 @@ impl Pwm {
/// `frequency` is a convenience method that calculates the frequency in hertz (Hz)
/// based on the configured period.
pub fn frequency(&self) -> Result<f64> {
let period = sysfs::period(self.channel as u8)? as f64;
let period = sysfs::period(self.chip, self.channel)? as f64;

Ok(if period == 0.0 {
0.0
Expand All @@ -354,7 +362,7 @@ impl Pwm {
/// `duty_cycle` is specified as a floating point value between `0.0` (0%) and `1.0` (100%).
pub fn set_frequency(&self, frequency: f64, duty_cycle: f64) -> Result<()> {
// Set duty cycle to 0 first in case the new period is shorter than the current duty cycle
let _ = sysfs::set_pulse_width(self.channel as u8, 0);
let _ = sysfs::set_pulse_width(self.chip, self.channel, 0);

// Convert to nanoseconds
let period = if frequency == 0.0 {
Expand All @@ -364,8 +372,8 @@ impl Pwm {
};
let pulse_width = period * duty_cycle.clamp(0.0, 1.0);

sysfs::set_period(self.channel as u8, period as u64)?;
sysfs::set_pulse_width(self.channel as u8, pulse_width as u64)?;
sysfs::set_period(self.chip, self.channel, period as u64)?;
sysfs::set_pulse_width(self.chip, self.channel, pulse_width as u64)?;

Ok(())
}
Expand All @@ -376,8 +384,8 @@ impl Pwm {
/// floating point value between `0.0` (0%) and `1.0` (100%) based on the configured
/// period and pulse width.
pub fn duty_cycle(&self) -> Result<f64> {
let period = sysfs::period(self.channel as u8)? as f64;
let pulse_width = sysfs::pulse_width(self.channel as u8)? as f64;
let period = sysfs::period(self.chip, self.channel)? as f64;
let pulse_width = sysfs::pulse_width(self.chip, self.channel)? as f64;

Ok(if period == 0.0 {
0.0
Expand All @@ -393,17 +401,17 @@ impl Pwm {
///
/// `duty_cycle` is specified as a floating point value between `0.0` (0%) and `1.0` (100%).
pub fn set_duty_cycle(&self, duty_cycle: f64) -> Result<()> {
let period = sysfs::period(self.channel as u8)? as f64;
let period = sysfs::period(self.chip, self.channel)? as f64;
let pulse_width = period * duty_cycle.clamp(0.0, 1.0);

sysfs::set_pulse_width(self.channel as u8, pulse_width as u64)?;
sysfs::set_pulse_width(self.chip, self.channel, pulse_width as u64)?;

Ok(())
}

/// Returns the polarity.
pub fn polarity(&self) -> Result<Polarity> {
Ok(sysfs::polarity(self.channel as u8)?)
Ok(sysfs::polarity(self.chip, self.channel)?)
}

/// Sets the polarity.
Expand All @@ -414,26 +422,26 @@ impl Pwm {
/// [`Normal`]: enum.Polarity.html#variant.Normal
/// [`Inverse`]: enum.Polarity.html#variant.Inverse
pub fn set_polarity(&self, polarity: Polarity) -> Result<()> {
sysfs::set_polarity(self.channel as u8, polarity)?;
sysfs::set_polarity(self.chip, self.channel, polarity)?;

Ok(())
}

/// Returns `true` if the PWM channel is enabled.
pub fn is_enabled(&self) -> Result<bool> {
Ok(sysfs::enabled(self.channel as u8)?)
Ok(sysfs::enabled(self.chip, self.channel)?)
}

/// Enables the PWM channel.
pub fn enable(&self) -> Result<()> {
sysfs::set_enabled(self.channel as u8, true)?;
sysfs::set_enabled(self.chip, self.channel, true)?;

Ok(())
}

/// Disables the PWM channel.
pub fn disable(&self) -> Result<()> {
sysfs::set_enabled(self.channel as u8, false)?;
sysfs::set_enabled(self.chip, self.channel, false)?;

Ok(())
}
Expand Down Expand Up @@ -461,8 +469,8 @@ impl Pwm {
impl Drop for Pwm {
fn drop(&mut self) {
if self.reset_on_drop {
let _ = sysfs::set_enabled(self.channel as u8, false);
let _ = sysfs::unexport(self.channel as u8);
let _ = sysfs::set_enabled(self.chip, self.channel, false);
let _ = sysfs::unexport(self.chip, self.channel);
}
}
}
Loading

0 comments on commit 6bbc5ef

Please sign in to comment.