Module imxrt_hal::flexpwm

Pulse width modulation.

Each PWM peripheral, Pwm, interacts with four submodules, Submodule. Each submodule acts as a timer with multiple compare registers, called ValueRegisters. A comparison event

• is signaled through a Status flag (see Submodule::status).
• can generate an interrupt (see Submodule::interrupts).
• sets a PWM Output high or low, depending on the turn on / off values.

Note: PWM outputs can also be manipulated directly with Submodule, without using Output.

The PWM driver does not implement any of the embedded-hal PWM traits. You should use these APIs to create your own PWM implementation that satisfies your driver.

Example

The PWM submodule counts over the range of i16 values. The counter runs at the IPG clock frequency. The PWM outputs produce independent, phase-shifted outputs.

use imxrt_hal as hal;
use imxrt_ral as ral;

use hal::flexpwm;

let pwm2 = unsafe { ral::pwm::PWM2::instance() };
let (mut pwm, (_, _, mut sm2, _)) = flexpwm::new(pwm2);

// Keep running in wait, debug modes.
sm2.set_debug_enable(true);
sm2.set_wait_enable(true);
// Run on the IPG clock.
sm2.set_clock_select(flexpwm::ClockSelect::Ipg);
// Divide the IPG clock by 1.
sm2.set_prescaler(flexpwm::Prescaler::Prescaler1);
// Allow PWM outputs to operate independently.
sm2.set_pair_operation(flexpwm::PairOperation::Independent);

// Reload every time the full reload value register compares.
sm2.set_load_mode(flexpwm::LoadMode::reload_full());
sm2.set_load_frequency(1);
// Count over the full range of i16 values.
sm2.set_initial_count(&pwm, i16::MIN);
sm2.set_value(flexpwm::FULL_RELOAD_VALUE_REGISTER, i16::MAX);

let gpio_b0_10 = // Handle to the pad
let gpio_b0_11 = // Handle to the pad
let output_a = flexpwm::Output::new_a(gpio_b0_10);
let output_b = flexpwm::Output::new_b(gpio_b0_11);
// Set the turn on / off count values.
output_a.set_turn_on(&sm2, i16::MIN / 2);
output_a.set_turn_off(&sm2, i16::MAX / 2);
// Output B generates the same duty cycle as A
// with a lagging phase shift of 5000 counts.
output_b.set_turn_on(&sm2, output_a.turn_on(&sm2) + 5000);
output_b.set_turn_off(&sm2, output_a.turn_off(&sm2) + 5000);

// Enable the PWM output.
output_a.set_output_enable(&mut pwm, true);
output_b.set_output_enable(&mut pwm, true);
// Load the values into the PWM registers.
sm2.set_load_ok(&mut pwm);
// Start running.
sm2.set_running(&mut pwm, true);

Structs

• Interrupts
  Interrupt flags.
• Mask
  Bitmask for representing submodules.
• Output
  A PWM output pin.
• Pwm
  A PWM peripheral.
• Status
  Status register flags.
• Submodule
  A PWM submodule.

Enums

• Channel
  PWM channels.
• ClockSelect
  PWM input clock selection.
• LoadMode
  PWM (re)load mode.
• PairOperation
  Describes how PWM channels A and B operate.
• Prescaler
  PWM clock prescaler.
• ValueRegister
  PWM value registers.

Constants

• FULL_RELOAD_VALUE_REGISTER
  The full reload value register.
• HALF_RELOAD_VALUE_REGISTER
  The half reload value register.

Functions

• new
  Create a PWM peripheral with its submodules.
• turn_off
  Returns the “turn off” value register for an output channel.
• turn_on
  Returns the “turn on” value register for an output channel.

Type Aliases

• Submodules
  Four submodules for the Nth PWM instance.