Automatic FSK polarity selection on TX side

This is done by simulating two cells with different polarities.
On first message from mobile station, the cell with the correct
polarity is used, the other is disabled.

On RX side the polarity is not selected, since FSK decoder detects
polarity for every frame.

1 files changed, 31 insertions, 11 deletions

diff --git a/src/cnetz/main.c b/src/cnetz/main.c
index 2e65756..87e1ec5 100644
--- a/src/cnetz/main.c
+++ b/src/cnetz/main.c
@@ -45,7 +45,8 @@ enum cnetz_chan_type chan_type[MAX_SENDER] = { CHAN_TYPE_OGK_SPK };
 int measure_speed = 0;
 double clock_speed[2] = { 0.0, 0.0 };
 int set_clock_speed = 0;
-double deviation = 0.5, noise = 0.0;
+const char *flip_polarity = "auto";
+double noise = 0.0;
 int ms_power = 0; /* 0..3 */
 int auth = 0;
 
@@ -60,12 +61,15 @@ void print_help(const char *arg0)
 	printf(" -S --clock-speed <rx ppm>,<tx ppm>\n");
 	printf("        Correct speed of sound card's clock. Use '-M' to measure speed for\n");
 	printf("        some hours after temperature has settled. The use these results to\n");
-	printf("	correct signal processing speed. After adjustment, the clock must match\n");
-	printf("	+- 1ppm or better. CORRECTING CLOCK SPEED IS REQUIRED! See\n");
+	printf("        correct signal processing speed. After adjustment, the clock must match\n");
+	printf("        +- 1ppm or better. CORRECTING CLOCK SPEED IS REQUIRED! See\n");
 	printf("        documentation on how to measure correct value.\n");
-	printf(" -F --flip-polarity\n");
-	printf("	Adjust, so the transmitter increases frequency, when positive levels\n");
-	printf("	are sent to sound device\n");
+	printf(" -F --flip-polarity no | yes auto\n");
+	printf("        Flip polarity of transmitted FSK signal. If yes, the sound card\n");
+	printf("        generates a negative signal rather than a positive one. If auto, the");
+	printf("        base station generates two virtual base stations with both polarities.\n");
+	printf("        Once a mobile registers, the correct polarity is selected and used.\n");
+	printf("        (default = %s)\n", flip_polarity);
 	printf(" -N --noise 0.0 .. 1.0 (default = %.1f)\n", noise);
 	printf("	Between frames on OgK, send noise at given level. Use 0.0 for Silence.\n");
 	printf(" -P --ms-power <power level>\n");
@@ -87,14 +91,14 @@ static int handle_options(int argc, char **argv)
 		{"channel-type", 1, 0, 't'},
 		{"measure-speed", 0, 0, 'M'},
 		{"clock-speed", 1, 0, 'S'},
-		{"flip-polarity", 0, 0, 'F'},
+		{"flip-polarity", 1, 0, 'F'},
 		{"noise", 1, 0, 'N'},
 		{"ms-power", 1, 0, 'P'},
 		{"authentication", 0, 0, 'A'},
 		{0, 0, 0, 0}
 	};
 
-	set_options_common("t:MS:FN:P:A", long_options_special);
+	set_options_common("t:MS:F:N:P:A", long_options_special);
 
 	while (1) {
 		int option_index = 0, c;
@@ -134,8 +138,17 @@ static int handle_options(int argc, char **argv)
 			skip_args += 2;
 			break;
 		case 'F':
-			deviation = -deviation;
-			skip_args += 1;
+			if (!strcasecmp(optarg, "no"))
+				flip_polarity = "no";
+			else if (!strcasecmp(optarg, "yes"))
+				flip_polarity = "yes";
+			else if (!strcasecmp(optarg, "auto"))
+				flip_polarity = "auto";
+			else {
+				fprintf(stderr, "Given polarity '%s' is illegal, see help!\n", optarg);
+				exit(0);
+			}
+			skip_args += 2;
 			break;
 		case 'N':
 			noise = strtold(optarg, NULL);
@@ -169,6 +182,7 @@ int main(int argc, char *argv[])
 	int skip_args;
 	const char *station_id = "";
 	int mandatory = 0;
+	int polarity;
 	int i;
 
 	/* init common tones */
@@ -251,9 +265,15 @@ int main(int argc, char *argv[])
 	if (i == num_kanal)
 		fprintf(stderr, "You did not define any SpK (speech) channel. You will not be able to make any call.\n");
 
+	polarity = 0; /* auto */
+	if (!strcmp(flip_polarity, "no"))
+		polarity = 1; /* positive */
+	if (!strcmp(flip_polarity, "yes"))
+		polarity = -1; /* negative */
+
 	/* create transceiver instance */
 	for (i = 0; i < num_kanal; i++) {
-		rc = cnetz_create(kanal[i], chan_type[i], sounddev[i], samplerate, cross_channels, rx_gain, auth, ms_power, (i == 0) ? measure_speed : 0, clock_speed, deviation, noise, do_pre_emphasis, do_de_emphasis, write_wave, read_wave, loopback);
+		rc = cnetz_create(kanal[i], chan_type[i], sounddev[i], samplerate, cross_channels, rx_gain, auth, ms_power, (i == 0) ? measure_speed : 0, clock_speed, polarity, noise, do_pre_emphasis, do_de_emphasis, write_wave, read_wave, loopback);
 		if (rc < 0) {
 			fprintf(stderr, "Failed to create \"Sender\" instance. Quitting!\n");
 			goto fail;