X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=src%2Fkernel%2Fao_freq.c;h=5443ea221afe904d8a26a68646c5c4ab1089cd9b;hb=b140da92536d7c48ba37868f1c2afce7bb86dfdb;hp=12496f6fdf785a2d94f5fac84c239092ede0e004;hpb=24167015705ae831692b95735968b04a876f935e;p=fw%2Faltos

diff --git a/src/kernel/ao_freq.c b/src/kernel/ao_freq.c
index 12496f6f..5443ea22 100644
--- a/src/kernel/ao_freq.c
+++ b/src/kernel/ao_freq.c
@@ -3,7 +3,8 @@
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; version 2 of the License.
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -20,36 +21,24 @@
 /*
  * The provided 'calibration' value is
  * that needed to tune the radio to precisely 434550kHz.
- * Use that to 'walk' to the target frequency by following
- * a 'bresenham' line from 434550kHz to the target
- * frequency, and updating the radio setting along the way
+ * The relation between value and freq is linear, so
+ * to get the value for an arbitrary frequency:
+ *
+ *	target_value   target_freq
+ *	------------ = ------------
+ *	 cal_value       cal_freq
+ *
+ *                     cal_value * target_freq
+ *	target_value = -----------------------
+ *                             cal_freq
  */
 
-int32_t ao_freq_to_set(int32_t freq, int32_t cal) __reentrant
+uint32_t ao_freq_to_set(uint32_t target_freq, uint32_t cal_value)
 {
-	static __pdata int32_t	set;
-	static __pdata uint8_t	neg;
-	static __pdata int32_t	error;
+	uint64_t	prod = (uint64_t) target_freq * (uint64_t) cal_value;
 
-	set = 0;
-	neg = 0;
-	error = -434550 / 2;
+	/* Round to nearest */
+	uint32_t target_value = (uint32_t) ((prod + (434550U / 2U)) / 434550U);
 
-	if ((freq -= 434550) < 0) {
-		neg = 1;
-		freq = -freq;
-	}
-	for (;;) {
-		if (error > 0) {
-			error -= 434550;
-			set++;
-		} else {
-			error += cal;
-			if (--freq < 0)
-				break;
-		}
-	}
-	if (neg)
-		set = -set;
-	return cal + set;
+	return target_value;
 }