From 0a618e37524a948ff78b5aa0d0d924176c7e6ebb Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Sat, 13 Sep 2014 20:29:11 +0200
Subject: Tool for calculating the I2S clock register values.

---
 tools/Makefile  |  4 +++
 tools/clkcalc.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 tools/Makefile
 create mode 100644 tools/clkcalc.c

diff --git a/tools/Makefile b/tools/Makefile
new file mode 100644
index 0000000..3cb72c9
--- /dev/null
+++ b/tools/Makefile
@@ -0,0 +1,4 @@
+all: clkcalc
+
+clkcalc: clkcalc.c
+	gcc clkcalc.c -o clkcalc
\ No newline at end of file
diff --git a/tools/clkcalc.c b/tools/clkcalc.c
new file mode 100644
index 0000000..2829ca9
--- /dev/null
+++ b/tools/clkcalc.c
@@ -0,0 +1,91 @@
+#include <stdio.h>
+
+double _fabs(double a)
+{
+	return a<0?a*-1:a;
+}
+
+typedef struct {
+	int pclkdiv_idx;
+	int bitrate;
+	int x;
+	int y;
+	double err;
+} result_t;
+
+static const int pclkdiv[] = { 1, 2, 4, 8 };
+
+
+int main(int argc, char *argv[])
+{
+	result_t best;
+	best.err = 999999;
+
+	if(argc < 3) {
+		printf("Usage: %s samplerate bitwidth channelcount\n", argv[0]);
+		printf("Example: 48KHz 16bit stereo\n");
+		printf("%s 48000 16 2\n", argv[0]);
+		return 1;
+	}
+
+	int fs = atoi(argv[1]);
+	int bw = atoi(argv[2]);
+	int ch = atoi(argv[3]);
+	
+	int target = fs * bw * ch;
+
+	int cclk = 100000000;
+
+	result_t res;
+	res.pclkdiv_idx = 0;
+
+	res.bitrate = 0;
+	res.x = 1;
+	res.y = 1;
+
+	for(;res.pclkdiv_idx < 4; res.pclkdiv_idx++) {
+
+		double clk = (cclk / pclkdiv[res.pclkdiv_idx]);
+
+		for(res.y = 1; res.y < 256; res.y++) {
+
+			double clk_y = clk / (double)res.y;
+
+			for(res.x = 1; res.x < 256; res.x++) {
+			
+				double clk_y_x_2 = (clk_y * (double)res.x) / 2.0;
+
+				for(res.bitrate = 0; res.bitrate < 65; res.bitrate++) {
+
+					double val = clk_y_x_2 / ((double)res.bitrate + 1.0);
+
+					res.err = _fabs(val - target);
+					if(res.err < best.err) best = res;
+
+					if(res.err == 0.0) {
+						goto found;
+					}
+				}
+			}
+		}
+	}
+
+	goto not_found;
+
+ found:
+	printf("Found:\n");
+	printf(" pclkdiv: %d\n", pclkdiv[res.pclkdiv_idx]);
+	printf(" bitrate: %d\n", res.bitrate);
+	printf(" x: %d\n", res.x);
+	printf(" y: %d\n", res.y);
+	return 0;
+
+ not_found:
+	printf("Not found - best was:\n");
+	printf(" pclkdiv: %d\n", pclkdiv[best.pclkdiv_idx]);
+	printf(" bitrate: %d\n", best.bitrate);
+	printf(" x: %d\n", best.x);
+	printf(" y: %d\n", best.y);
+	printf(" err: %f\n", best.err);
+	return 1;
+}
-- 
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