Save a working blinkenlight as a test

hello_gradient/Cargo.lock

@@ -108,8 +108,10 @@ dependencies = [
 name = "hello_gradient"
 version = "0.1.0"
 dependencies = [
+ "itsybitsy_m0 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "itsybitsy_m0_lights 0.1.0",
  "lights 0.1.0",
+ "panic-halt 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]

hello_gradient/Cargo.toml

@@ -10,5 +10,7 @@ codegen-units = 1
 debug = true
 
 [dependencies]
+itsybitsy_m0 = "0.5"
 lights = { path = "../lights" }
 lights_hal = { path = "../itsybitsy_m0_lights", package = "itsybitsy_m0_lights" }
+panic-halt = "0.2"

hello_gradient/src/bin/sanity_test.rs

@@ -0,0 +1,32 @@
+#![no_std]
+#![no_main]
+
+extern crate itsybitsy_m0 as hal;
+extern crate panic_halt;
+
+use hal::clock::GenericClockController;
+use hal::delay::Delay;
+use hal::prelude::*;
+use hal::entry;
+use hal::pac::{CorePeripherals, Peripherals};
+
+#[entry]
+fn main() -> ! {
+    let mut peripherals = Peripherals::take().unwrap();
+    let core = CorePeripherals::take().unwrap();
+    let mut clocks = GenericClockController::with_internal_32kosc(
+        peripherals.GCLK,
+        &mut peripherals.PM,
+        &mut peripherals.SYSCTRL,
+        &mut peripherals.NVMCTRL,
+    );
+    let mut pins = hal::Pins::new(peripherals.PORT);
+    let mut red_led = pins.d13.into_open_drain_output(&mut pins.port);
+    let mut delay = Delay::new(core.SYST, &mut clocks);
+    loop {
+        delay.delay_ms(200u8);
+        red_led.set_high().unwrap();
+        delay.delay_ms(200u8);
+        red_led.set_low().unwrap();
+    }
+}