initial commit with my changes

examples/exception.rs

@@ -0,0 +1,37 @@
+//! Overriding an exception handler
+//!
+//! You can override an exception handler using the [`#[exception]`][1] attribute.
+//!
+//! [1]: https://rust-embedded.github.io/cortex-m-rt/0.6.1/cortex_m_rt_macros/fn.exception.html
+//!
+//! ---
+
+#![deny(unsafe_code)]
+#![no_main]
+#![no_std]
+
+use panic_halt as _;
+
+use cortex_m::peripheral::syst::SystClkSource;
+use cortex_m::Peripherals;
+use cortex_m_rt::{entry, exception};
+use cortex_m_semihosting::hprint;
+
+#[entry]
+fn main() -> ! {
+    let p = Peripherals::take().unwrap();
+    let mut syst = p.SYST;
+
+    // configures the system timer to trigger a SysTick exception every second
+    syst.set_clock_source(SystClkSource::Core);
+    syst.set_reload(8_000_000); // period = 1s
+    syst.enable_counter();
+    syst.enable_interrupt();
+
+    loop {}
+}
+
+#[exception]
+fn SysTick() {
+    hprint!(".").unwrap();
+}