Do radio settings solely by frequency

Compute the radio setting needed based on the calibration value
provided and the requested frequency.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/src/core/ao_freq.c b/src/core/ao_freq.c
new file mode 100644
index 00000000..13bcb383
--- /dev/null
+++ b/src/core/ao_freq.c
@@ -0,0 +1,52 @@
+/*
+ * Copyright © 2012 Keith Packard <keithp@keithp.com>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <ao.h>
+
+/*
+ * 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
+ */
+
+int32_t ao_freq_to_set(int32_t freq, int32_t cal) {
+	__pdata int32_t	set = 0;
+	uint8_t	neg = 0;
+	__pdata int32_t	error = -434550 / 2;
+
+	freq -= 434550;
+	if (freq < 0) {
+		neg = 1;
+		freq = -freq;
+	}
+	for (;;) {
+		if (freq == 0 && error <= 0)
+			break;
+		if (error > 0) {
+			error -= 434550;
+			set++;
+		} else {
+			error += cal;
+			freq--;
+		}
+	}
+	if (neg)
+		set = -set;
+	return cal + set;
+}