Make led 2 fade through spectrum

Cargo.toml

@@ -8,5 +8,6 @@ readme = "README.md"
 [dependencies]
 cortex-m = "0.6.4"
 cortex-m-rt = "0.6.13"
+nb = "1"
 panic-halt = "0.2.0"
 stm32f0xx-hal = { version = "0.18.0", features = ["rt", "stm32f072"] }

src/main.rs

@@ -20,9 +20,12 @@
 #![no_main]
 
 use cortex_m_rt::entry;
+use nb::block;
 use panic_halt as _;
 use stm32f0xx_hal::pac::Peripherals;
 use stm32f0xx_hal::prelude::*;
+use stm32f0xx_hal::pwm::tim3;
+use stm32f0xx_hal::timers::Timer;
 
 #[entry]
 fn main() -> ! {
@@ -33,24 +36,61 @@ fn main() -> ! {
     let gpioa = p.GPIOA.split(&mut rcc);
     let gpiob = p.GPIOB.split(&mut rcc);
 
-    let (mut led1_b, mut led1_g, mut led1_r, mut led2_g, mut led2_r, mut led2_b) = cortex_m::interrupt::free(|cs| (
+    let (mut led1_b, mut led1_g, mut led1_r) = cortex_m::interrupt::free(|cs| (
         gpioa.pa0.into_push_pull_output(cs),
         gpioa.pa1.into_push_pull_output(cs),
         gpioa.pa2.into_push_pull_output(cs),
-        gpiob.pb0.into_push_pull_output(cs),
-        gpiob.pb1.into_push_pull_output(cs),
-        gpiob.pb5.into_push_pull_output(cs),
     ));
+
     led1_r.set_high().ok(); //   0
     led1_g.set_high().ok(); //   0
     led1_b.set_low().ok();  // 255
     // ^ blue
-    led2_r.set_high().ok(); //   0
-    led2_g.set_low().ok();  // 255
-    led2_b.set_low().ok();  // 255
-    // ^ cyan
 
+    let led2_channels = cortex_m::interrupt::free(|cs| (
+        gpiob.pb4.into_alternate_af1(cs),
+        gpiob.pb5.into_alternate_af1(cs),
+        gpiob.pb0.into_alternate_af1(cs),
+        gpiob.pb1.into_alternate_af1(cs),
+    ));
+
+    let (_, mut led2_b, mut led2_g, mut led2_r) = tim3(p.TIM3, led2_channels, &mut rcc, 20u32.khz());
+    let led2_r_max = led2_r.get_max_duty();
+    let led2_g_max = led2_g.get_max_duty();
+    let led2_b_max = led2_b.get_max_duty();
+
+    led2_r.set_duty(led2_r_max); // 0
+    led2_g.set_duty(led2_g_max); // 0
+    led2_b.set_duty(led2_b_max); // 0
+    // ^ violet
+
+    led2_r.enable();
+    led2_g.enable();
+    led2_b.enable();
+
+    let mut timer = Timer::tim1(p.TIM1, 100.hz(), &mut rcc);
+
+    let mut hue = 0;
     loop {
-        cortex_m::asm::nop();
+        let h_i = hue / 60;
+        let f = hue as f32 / 60.0 - h_i as f32;
+        let q = 1.0 - f;
+
+        let (r, g, b) = match h_i {
+            0 => (1.0,   f, 0.0),
+            1 => (  q, 1.0, 0.0),
+            2 => (0.0, 1.0,   f),
+            3 => (0.0,   q, 1.0),
+            4 => (  f, 0.0, 1.0),
+            5 => (1.0, 0.0,   q),
+            _ => (0.0, 0.0, 0.0),
+        };
+        led2_r.set_duty(led2_r_max - (led2_r_max as f32 * r) as u16);
+        led2_g.set_duty(led2_g_max - (led2_g_max as f32 * g) as u16);
+        led2_b.set_duty(led2_b_max - (led2_b_max as f32 * b) as u16);
+
+        hue = (hue + 1) % 360;
+
+        block!(timer.wait()).ok();
     }
 }