make sound work

lib/FatFs_SPI/include/util.h

@@ -0,0 +1,68 @@
+/* util.h
+Copyright 2021 Carl John Kugler III
+
+Licensed under the Apache License, Version 2.0 (the License); you may not use 
+this file except in compliance with the License. You may obtain a copy of the 
+License at
+
+   http://www.apache.org/licenses/LICENSE-2.0 
+Unless required by applicable law or agreed to in writing, software distributed 
+under the License is distributed on an AS IS BASIS, WITHOUT WARRANTIES OR 
+CONDITIONS OF ANY KIND, either express or implied. See the License for the 
+specific language governing permissions and limitations under the License.
+*/
+#ifndef _UTIL_H_
+#define _UTIL_H_
+
+#include <stddef.h>    
+#include <stdint.h>
+
+#include "hardware/structs/scb.h"
+
+// works with negative index
+static inline int wrap_ix(int index, int n)
+{
+    return ((index % n) + n) % n;
+}
+
+__attribute__((always_inline)) static inline uint32_t calculate_checksum(uint32_t const *p, size_t const size){
+	uint32_t checksum = 0;
+	for (uint32_t i = 0; i < (size/sizeof(uint32_t))-1; i++){
+		checksum ^= *p;
+		p++;
+	}
+	return checksum;
+}
+
+
+// from Google Chromium's codebase:
+#ifndef COUNT_OF    
+#define COUNT_OF(x) ((sizeof(x)/sizeof(0[x])) / ((size_t)(!(sizeof(x) % sizeof(0[x])))))
+#endif
+
+__attribute__((always_inline)) static inline void __DSB(void) {
+    __asm volatile("dsb 0xF" ::: "memory");
+}
+
+// Patterned after CMSIS NVIC_SystemReset
+__attribute__((__noreturn__)) static inline void system_reset() {
+    __DSB(); /* Ensure all outstanding memory accesses included
+         buffered write are completed before reset */
+    scb_hw->aircr = ((0x5FAUL << 16U) | (1UL << 2U));
+    __DSB(); /* Ensure completion of memory access */
+    for (;;) {
+        __asm volatile("nop");
+    }
+}
+
+/**
+  \brief   Disable IRQ Interrupts
+  \details Disables IRQ interrupts by setting the I-bit in the CPSR.
+           Can only be executed in Privileged modes.
+ */
+__attribute__((always_inline)) static inline void __disable_irq(void) {
+    __asm volatile("cpsid i" : : : "memory");
+}
+
+#endif
+/* [] END OF FILE */