添加一些关于midi播放的项目

Midi/music-box-nv32-master/nv32lib/common/system_nv32.h

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+/*
+ * @brief Device specific configuration file for NV32 (header file)
+ *
+ * Provides a system configuration function and a global variable that contains
+ * the system frequency. It configures the device and initializes the oscillator
+ * (PLL) that is part of the microcontroller device.
+ */
+
+#ifndef SYSTEM_NV32_H_
+#define SYSTEM_NV32_H_                        /**< Symbol preventing repeated inclusion */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+
+/**
+ * @brief System clock frequency (core clock)
+ *
+ * The system clock frequency supplied to the SysTick timer and the processor
+ * core clock. This variable can be used by the user application to setup the
+ * SysTick timer or configure other parameters. It may also be used by debugger to
+ * query the frequency of the debug timer or configure the trace clock speed
+ * SystemCoreClock is initialized with a correct predefined value.
+ */
+extern uint32_t SystemCoreClock;
+
+/**
+ * @brief Setup the microcontroller system.
+ *
+ * Typically this function configures the oscillator (PLL) that is part of the
+ * microcontroller device. For systems with variable clock speed it also updates
+ * the variable SystemCoreClock. SystemInit is called from startup_device file.
+ */
+void SystemInit (void);
+
+/**
+ * @brief Updates the SystemCoreClock variable.
+ *
+ * It must be called whenever the core clock is changed during program
+ * execution. SystemCoreClockUpdate() evaluates the clock register settings and calculates
+ * the current core clock.
+ */
+void SystemCoreClockUpdate (void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* #if !defined(SYSTEM_NV32_H_) */