k20: Introduce app_blink_k20_isr.

Rakefile

@@ -175,7 +175,7 @@ end
 desc "Build all applications"
 case ENV['PLATFORM']
 when 'k20'
-  task :build_all => [:build_blink_k20]
+  task :build_all => [:build_blink_k20, :build_blink_k20_isr]
 when 'stm32f4'
   task :build_all => [:build_blink_stm32f4]
 else

apps/app_blink_k20_isr.rs

@@ -0,0 +1,54 @@
+#![feature(phase)]
+#![feature(asm)]
+#![crate_type="staticlib"]
+#![no_std]
+
+extern crate core;
+extern crate zinc;
+
+use core::intrinsics::volatile_load;
+
+use core::option::Some;
+use zinc::hal::k20::{pin, watchdog};
+use zinc::hal::pin::GPIO;
+use zinc::hal::cortex_m4::systick;
+use zinc::util::support::wfi;
+
+static mut i: u32 = 0;
+static mut global_on: u32 = 0;
+
+#[allow(dead_code)]
+#[no_split_stack]
+#[no_mangle]
+pub unsafe extern fn isr_systick() {
+    i += 1;
+    if i > 100 {
+      i = 0;
+      global_on = !global_on;
+    }
+}
+
+#[no_mangle]
+#[no_split_stack]
+#[allow(dead_code)]
+pub fn main() {
+  zinc::hal::mem_init::init_stack();
+  zinc::hal::mem_init::init_data();
+  watchdog::init(watchdog::Disabled);
+
+  // Pins for MC HCK (http://www.mchck.org/)
+  let led1 = pin::Pin::new(pin::PortB, 16, pin::GPIO, Some(zinc::hal::pin::Out));
+
+  systick::setup(systick::ten_ms().unwrap_or(480000));
+  systick::enable();
+  systick::enable_irq();
+
+  loop {
+    let on: bool = unsafe { volatile_load(&global_on as *const u32) == 0 };
+      match on {
+        true  => led1.set_high(),
+        false => led1.set_low(),
+      }
+      wfi();
+  }
+}

src/zinc/util/support.rs

@@ -69,3 +69,15 @@ pub fn nop() {
 /// NOP instruction (mock)
 pub fn nop() {
 }
+
+#[cfg(not(test))]
+#[inline(always)]
+/// WFI instruction
+pub fn wfi() {
+    unsafe { asm!("wfi" :::: "volatile"); }
+}
+
+#[cfg(test)]
+/// WFI instruction (mock)
+pub fn wfi() {
+}