rp: add PWM api

examples/rp/src/bin/pwm.rs

@@ -0,0 +1,27 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::*;
+use embassy_embedded_hal::SetConfig;
+use embassy_executor::Spawner;
+use embassy_rp::pwm::{Config, Pwm};
+use embassy_time::{Duration, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_rp::init(Default::default());
+
+    let mut c: Config = Default::default();
+    c.top = 0x8000;
+    c.compare_b = 8;
+    let mut pwm = Pwm::new_output_b(p.PWM_CH4, p.PIN_25, c.clone());
+
+    loop {
+        info!("current LED duty cycle: {}/32768", c.compare_b);
+        Timer::after(Duration::from_secs(1)).await;
+        c.compare_b = c.compare_b.rotate_left(4);
+        pwm.set_config(&c);
+    }
+}