Adding libugba interrupt handler

examples/_lib/libugba/include/timer.h

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright (c) 2020 Antonio Niño Díaz
+
+#ifndef TIMER_H__
+#define TIMER_H__
+
+#include "definitions.h"
+
+// Start timer. The value passed to prescaler can be 1, 64, 256 or 1024.
+EXPORT_API
+void TM_TimerStart(int index, uint16_t reload_value, int prescaler,
+                   int enable_irq);
+
+// Start timer in cascade mode. Note that the prescaler value is ignored in this
+// mode, so it isn't needed.
+EXPORT_API
+void TM_TimerStartCascade(int index, uint16_t period_ticks, int enable_irq);
+
+// Start timer that is triggered every `period_ms` milliseconds. Internally it
+// looks for the lowest prescaler that allows this period (to have the best
+// accuracy). It returns 0 on success.
+EXPORT_API
+int TM_TimerStartMs(int index, uint32_t period_ms, int enable_irq);
+
+// Stop the specified timer.
+EXPORT_API
+void TM_TimerStop(int index);
+
+#endif // TIMER_H__
+