1 files changed, 83 insertions, 0 deletions
diff --git a/02-usart/src/core/irq.c b/02-usart/src/core/irq.c
new file mode 100644
index 0000000..c9b93c2
--- /dev/null
+++ b/02-usart/src/core/irq.c
@@ -0,0 +1,83 @@
+#include "core/irq.h"
+#include "core/gpio.h"
+
+#include "arch.h"
+#include "delay.h"
+
+#ifdef ARCH_STM32L4
+
+#define IRQ_RESERVED(n)
+#define IRQ(name, uname_, n) \
+  void WEAK name () { \
+    unhandled_isr(n); \
+  }
+#include "core/isrs.inc"
+#undef IRQ_RESERVED
+#undef IRQ
+
+void isr_simple_pin_on()
+{
+  __IO gpio_port_t* port_b = enable_gpio(GPIO_PORT_B);
+  gpio_output_pin_t pin3 = set_gpio_pin_output(port_b, PIN_3);
+
+  pin_on(pin3);
+}
+
+#define IRQ_RESERVED(n) 0,
+#define IRQ(name, uname_, n) name,
+const void* vectors[] __attribute__((section(".vectors"))) = {
+    (void*)0x2000c000, /* Top of stack at top of sram1. 48k */
+#include "core/isrs.inc"
+};
+#undef IRQ_RESERVED
+#undef IRQ
+
+/* Encodes the provided number as a series of flashes on the on-board
+ * LED. The flashes follow as such:
+ *
+ * Before the bits of the code are flashed, a rapid succession of 20 flashes
+ * followed by a pause will occur indicating that the next 8 flashes indicate
+ * the bits of the provided code.
+ *
+ * Eoch of the next eight flashes indicate either a 1 or 0 depending on the
+ * length of flash. The first flash is the least-significant bit, the next the
+ * second least, the third third least, etc.
+ *
+ * - A quick flash followed by a long pause indicates a 0 bit.
+ * - A "long" flash followed by a equally long pause indicates a 1 bit.
+ */
+void unhandled_isr(uint8_t number)
+{
+  __IO gpio_port_t* port_b = enable_gpio(GPIO_PORT_B);
+  gpio_output_pin_t pin3 = set_gpio_pin_output(port_b, PIN_3);
+  for (;;) {
+    for (int i = 0; i < 20; ++ i) {
+       pin_on(pin3);
+       delay(1000000);
+       pin_off(pin3);
+       delay(1000000);
+    }
+    delay(50000000);
+
+    int n = number;
+    for (int i = 0; i < 8; ++ i) {
+      if (n & 1) {
+       // LSB is a 1
+       pin_on(pin3);
+       delay(15000000);
+       pin_off(pin3);
+       delay(15000000);
+      } else {
+       // LSB is a 0
+       pin_on(pin3);
+       delay(1000000);
+       pin_off(pin3);
+       delay(29000000);
+      }
+
+      n >>= 1;
+    }
+  }
+}
+
+#endif