Blinky (in theory)...

src/main.rs

@@ -6,12 +6,34 @@
 use panic_halt;
 
 use cortex_m_rt::entry;
-use stm32l4xx_hal::{pac, rcc::RccExt};
+use stm32l4xx_hal::{prelude::*, flash::FlashExt, gpio::GpioExt, pac, pwr::PwrExt, rcc::RccExt, time::Hertz, delay::Delay};
 
 #[entry]
 fn main() -> ! {
     let dp = pac::Peripherals::take().unwrap();
     let cp = cortex_m::Peripherals::take().unwrap();
 
-    loop {}
+    let mut flash = dp.FLASH.constrain();
+    let mut rcc = dp.RCC.constrain();
+    let mut pwr = dp.PWR.constrain(&mut rcc.apb1r1);
+
+    // Ok for now, but ideally actually think about what this does (especially when we have tim).
+    let clocks = rcc
+        .cfgr
+        .hclk(Hertz::MHz(8))
+        .freeze(&mut flash.acr, &mut pwr);
+
+    let mut gpioa = dp.GPIOA.split(&mut rcc.ahb2);
+    let mut led_pin = gpioa
+        .pa0
+        .into_push_pull_output(&mut gpioa.moder, &mut gpioa.otyper);
+
+    let mut timer = Delay::new(cp.SYST, clocks);
+
+    loop {
+        timer.delay_ms(1000_u32);
+        led_pin.set_high();
+        timer.delay_ms(1000_u32);
+        led_pin.set_low();
+    }
 }