GK SDK 源码库: XMIPCLinuxV100R005C00SPC030 (kernel/tools/open_source excluded)

source/bootloader/u-boot-2020.01/drivers/sound/sound.c

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+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2012 Samsung Electronics
+ * R. Chandrasekar <rcsekar@samsung.com>
+ */
+
+#include <common.h>
+#include <sound.h>
+
+void sound_create_square_wave(uint sample_rate, unsigned short *data, int size,
+			      uint freq, uint channels)
+{
+	const unsigned short amplitude = 16000; /* between 1 and 32767 */
+	const int period = freq ? sample_rate / freq : 0;
+	const int half = period / 2;
+
+	assert(freq);
+
+	/* Make sure we don't overflow our buffer */
+	if (size % 2)
+		size--;
+
+	while (size) {
+		int i, j;
+
+		for (i = 0; size && i < half; i++) {
+			size -= 2;
+			for (j = 0; j < channels; j++)
+				*data++ = amplitude;
+		}
+		for (i = 0; size && i < period - half; i++) {
+			size -= 2;
+			for (j = 0; j < channels; j++)
+				*data++ = -amplitude;
+		}
+	}
+}