4 files changed, 58 insertions, 21 deletions

diff --git a/embassy-nrf/src/pwm.rs b/embassy-nrf/src/pwm.rs
index 41dcce049..94dfdeda6 100644
--- a/embassy-nrf/src/pwm.rs
+++ b/embassy-nrf/src/pwm.rs
@@ -31,6 +31,8 @@ pub struct SequencePwm<'d, T: Instance> {
     ch1: Option<AnyPin>,
     ch2: Option<AnyPin>,
     ch3: Option<AnyPin>,
+    sequence0: Option<Sequence<'d>>,
+    sequence1: Option<Sequence<'d>>,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -125,11 +127,13 @@ impl<'d, T: Instance> SequencePwm<'d, T> {
             ch1: ch1.degrade_optional(),
             ch2: ch2.degrade_optional(),
             ch3: ch3.degrade_optional(),
+            sequence0: None,
+            sequence1: None,
         })
     }
 
     /// Start or restart playback. Takes at least one sequence along with its
-    /// configuration. Optionally takes a second sequence and/or its configuration.
+    /// configuration. Optionally takes a second sequence and its configuration.
     /// In the case where no second sequence is provided then the first sequence
     /// is used. The sequence mode applies to both sequences combined as one.
     #[inline(always)]
@@ -152,7 +156,7 @@ impl<'d, T: Instance> SequencePwm<'d, T> {
             return Err(Error::SequenceTimesAtLeastOne);
         }
 
-        self.stop();
+        let _ = self.stop();
 
         let r = T::regs();
 
@@ -222,6 +226,9 @@ impl<'d, T: Instance> SequencePwm<'d, T> {
             }
         }
 
+        self.sequence0 = Some(sequence0);
+        self.sequence1 = sequence1;
+
         Ok(())
     }
 
@@ -326,9 +333,10 @@ impl<'d, T: Instance> SequencePwm<'d, T> {
     }
 
     /// Stop playback. Disables the peripheral. Does NOT clear the last duty
-    /// cycle from the pin.
+    /// cycle from the pin. Returns any sequences previously provided to
+    /// `start` so that they may be further mutated.
     #[inline(always)]
-    pub fn stop(&self) {
+    pub fn stop(&mut self) -> (Option<Sequence<'d>>, Option<Sequence<'d>>) {
         let r = T::regs();
 
         r.shorts.reset();
@@ -339,6 +347,8 @@ impl<'d, T: Instance> SequencePwm<'d, T> {
         r.tasks_stop.write(|w| unsafe { w.bits(0x01) });
 
         r.enable.write(|w| w.enable().disabled());
+
+        (self.sequence0.take(), self.sequence1.take())
     }
 }
 
@@ -346,7 +356,7 @@ impl<'a, T: Instance> Drop for SequencePwm<'a, T> {
     fn drop(&mut self) {
         let r = T::regs();
 
-        self.stop();
+        let _ = self.stop();
 
         if let Some(pin) = &self.ch0 {
             pin.set_low();
@@ -415,13 +425,13 @@ impl Default for SequenceConfig {
 #[non_exhaustive]
 pub struct Sequence<'d> {
     /// The words comprising the sequence. Must not exceed 32767 words.
-    pub words: &'d [u16],
+    pub words: &'d mut [u16],
     /// Configuration associated with the sequence.
     pub config: SequenceConfig,
 }
 
 impl<'d> Sequence<'d> {
-    pub fn new(words: &'d [u16], config: SequenceConfig) -> Self {
+    pub fn new(words: &'d mut [u16], config: SequenceConfig) -> Self {
         Self { words, config }
     }
 }
diff --git a/examples/nrf/src/bin/pwm_sequence.rs b/examples/nrf/src/bin/pwm_sequence.rs
index 78787d531..6fb861e8f 100644
--- a/examples/nrf/src/bin/pwm_sequence.rs
+++ b/examples/nrf/src/bin/pwm_sequence.rs
@@ -13,8 +13,8 @@ use embassy_nrf::Peripherals;
 
 #[embassy::main]
 async fn main(_spawner: Spawner, p: Peripherals) {
-    let seq_words_1: [u16; 5] = [1000, 250, 100, 50, 0];
-    let seq_words_2: [u16; 5] = [0, 50, 100, 250, 1000];
+    let mut seq_words_1: [u16; 5] = [1000, 250, 100, 50, 0];
+    let mut seq_words_2: [u16; 5] = [0, 50, 100, 250, 1000];
 
     let mut config = Config::default();
     config.prescaler = Prescaler::Div128;
@@ -30,7 +30,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
         p.PWM0, p.P0_13, NoPin, NoPin, NoPin, config,
     ));
     let _ = pwm.start(
-        Sequence::new(&seq_words_1, seq_config.clone()),
+        Sequence::new(&mut seq_words_1, seq_config.clone()),
         None,
         SequenceMode::Infinite,
     );
@@ -41,7 +41,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     info!("pwm starting with another sequence!");
 
     let _ = pwm.start(
-        Sequence::new(&seq_words_2, seq_config),
+        Sequence::new(&mut seq_words_2, seq_config),
         None,
         SequenceMode::Infinite,
     );
diff --git a/examples/nrf/src/bin/pwm_sequence_ppi.rs b/examples/nrf/src/bin/pwm_sequence_ppi.rs
index c80820f84..f5d734bb1 100644
--- a/examples/nrf/src/bin/pwm_sequence_ppi.rs
+++ b/examples/nrf/src/bin/pwm_sequence_ppi.rs
@@ -16,7 +16,7 @@ use embassy_nrf::Peripherals;
 
 #[embassy::main]
 async fn main(_spawner: Spawner, p: Peripherals) {
-    let seq_words: [u16; 5] = [1000, 250, 100, 50, 0];
+    let mut seq_words: [u16; 5] = [1000, 250, 100, 50, 0];
 
     let mut config = Config::default();
     config.prescaler = Prescaler::Div128;
@@ -32,7 +32,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     ));
 
     let _ = pwm.start(
-        Sequence::new(&seq_words, seq_config),
+        Sequence::new(&mut seq_words, seq_config),
         None,
         SequenceMode::Infinite,
     );
diff --git a/examples/nrf/src/bin/pwm_sequence_ws2812b.rs b/examples/nrf/src/bin/pwm_sequence_ws2812b.rs
index 2fb37015d..0ce79cbe0 100644
--- a/examples/nrf/src/bin/pwm_sequence_ws2812b.rs
+++ b/examples/nrf/src/bin/pwm_sequence_ws2812b.rs
@@ -15,7 +15,9 @@ use embassy_nrf::Peripherals;
 
 // WS2812B LED light demonstration. Drives just one light.
 // The following reference on WS2812B may be of use:
-// https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf
+// https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf.
+// This demo lights up a single LED in blue. It then proceeds
+// to pulsate the LED rapidly.
 
 // In the following declarations, setting the high bit tells the PWM
 // to reverse polarity, which is what the WS2812B expects.
@@ -29,17 +31,17 @@ const RES: u16 = 0x8000;
 #[embassy::main]
 async fn main(_spawner: Spawner, p: Peripherals) {
     // Declare the bits of 24 bits
-    let blue_seq_words = [
+    let mut color_seq_words = [
         T0H, T0H, T0H, T0H, T0H, T0H, T0H, T0H, // G
         T0H, T0H, T0H, T0H, T0H, T0H, T0H, T0H, // R
         T1H, T1H, T1H, T1H, T1H, T1H, T1H, T1H, // B
     ];
-    let blue_seq = Sequence::new(&blue_seq_words, SequenceConfig::default());
+    let color_seq = Sequence::new(&mut color_seq_words, SequenceConfig::default());
 
-    let reset_seq_words = [RES; 1];
+    let mut reset_seq_words = [RES; 1];
     let mut reset_seq_config = SequenceConfig::default();
     reset_seq_config.end_delay = 799; // 50us (20 ticks * 40) - 1 tick because we've already got one RES;
-    let reset_seq = Sequence::new(&reset_seq_words, reset_seq_config);
+    let reset_seq = Sequence::new(&mut reset_seq_words, reset_seq_config);
 
     let mut config = Config::default();
     config.sequence_load = SequenceLoad::Common;
@@ -49,8 +51,33 @@ async fn main(_spawner: Spawner, p: Peripherals) {
         p.PWM0, p.P1_05, NoPin, NoPin, NoPin, config,
     ));
 
-    unwrap!(pwm.start(blue_seq, Some(reset_seq), SequenceMode::Times(2)));
+    unwrap!(pwm.start(color_seq, Some(reset_seq), SequenceMode::Times(2)));
 
-    Timer::after(Duration::from_millis(20000)).await;
-    info!("Program stopped");
+    Timer::after(Duration::from_millis(1000)).await;
+
+    let mut color_bit = 16;
+    let mut bit_value = T0H;
+
+    loop {
+        if let (Some(color_seq), Some(reset_seq)) = pwm.stop() {
+            color_seq.words[color_bit] = bit_value;
+            unwrap!(pwm.start(color_seq, Some(reset_seq), SequenceMode::Times(2)));
+        }
+
+        Timer::after(Duration::from_millis(50)).await;
+
+        if bit_value == T0H {
+            if color_bit == 20 {
+                bit_value = T1H;
+            } else {
+                color_bit += 1;
+            }
+        } else {
+            if color_bit == 16 {
+                bit_value = T0H;
+            } else {
+                color_bit -= 1;
+            }
+        }
+    }
 }