Merge #591

591: PWM WS2812B example and flexible sequence config r=Dirbaio a=huntc

I've permitted the PWM sequences to be mutated on stopping the PWM by associating them with a new  `SingleSequencer` structure. This is so that we can perform effects on the LEDs (and other use-cases, I'm sure!). The example has been updated to illustrate the use of this by flashing a WS2812B LED.

There's also a `Sequencer` structure for more sophisticated PWM interactions, along with a `pwm_double_sequence`  example to illustrate.

These changes should make it possible to attain all of the nRF PWM functionality available.

Co-authored-by: huntc <[email protected]>

1 files changed, 46 insertions, 0 deletions

diff --git a/examples/nrf/src/bin/pwm_double_sequence.rs b/examples/nrf/src/bin/pwm_double_sequence.rs
new file mode 100644
index 000000000..269015f4a
--- /dev/null
+++ b/examples/nrf/src/bin/pwm_double_sequence.rs
@@ -0,0 +1,46 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+use defmt::*;
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_nrf::gpio::NoPin;
+use embassy_nrf::pwm::{
+    Config, Prescaler, Sequence, SequenceConfig, SequenceMode, SequencePwm, Sequencer,
+    StartSequence,
+};
+use embassy_nrf::Peripherals;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    let seq_words_0: [u16; 5] = [1000, 250, 100, 50, 0];
+    let seq_words_1: [u16; 4] = [50, 100, 250, 1000];
+
+    let mut config = Config::default();
+    config.prescaler = Prescaler::Div128;
+    // 1 period is 1000 * (128/16mhz = 0.000008s = 0.008ms) = 8us
+    // but say we want to hold the value for 5000ms
+    // so we want to repeat our value as many times as necessary until 5000ms passes
+    // want 5000/8 = 625 periods total to occur, so 624 (we get the one period for free remember)
+    let mut seq_config = SequenceConfig::default();
+    seq_config.refresh = 624;
+    // thus our sequence takes 5 * 5000ms or 25 seconds
+
+    let mut pwm = unwrap!(SequencePwm::new(
+        p.PWM0, p.P0_13, NoPin, NoPin, NoPin, config,
+    ));
+
+    let sequence_0 = Sequence::new(&seq_words_0, seq_config.clone());
+    let sequence_1 = Sequence::new(&seq_words_1, seq_config);
+    let sequencer = Sequencer::new(&mut pwm, sequence_0, Some(sequence_1));
+    unwrap!(sequencer.start(StartSequence::Zero, SequenceMode::Loop(1)));
+
+    // we can abort a sequence if we need to before its complete with pwm.stop()
+    // or stop is also implicitly called when the pwm peripheral is dropped
+    // when it goes out of scope
+    Timer::after(Duration::from_millis(40000)).await;
+    info!("pwm stopped early!");
+}