Fixed some bugs where I was treating sample data as an integer. Allows use with UHD without multiplying everything up by 64K. =)

Also changed the reference level printout to show dB instead of sample value. This seems more useful. 0dB is full scale.

src/lib/air_modes_framer.cc

@@ -39,7 +39,7 @@ int air_modes_framer::work(int noutput_items,
 
 	int size = noutput_items - d_check_width; //need to be able to look ahead a full frame
 
-	int reference_level = 0;
+	float reference_level = 0;
 	framer_packet_type packet_attrib;
 
 	for(int i = 0; i < size; i++) {
@@ -67,7 +67,7 @@ int air_modes_framer::work(int noutput_items,
 		//NOTE: you can change the default here to be short packet, and then check for a long packet. don't know which way is better.
 
 		for(int j = (65 * d_samples_per_symbol); j < (70 * d_samples_per_symbol); j += d_samples_per_symbol) {
-			int t_max = (bit_energy(&inraw[i+j], d_samples_per_chip) > bit_energy(&inraw[i+j+d_samples_per_chip], d_samples_per_chip)) ? bit_energy(&inraw[i+j], d_samples_per_chip) : bit_energy(&inraw[i+j+d_samples_per_chip], d_samples_per_chip);
+			float t_max = (bit_energy(&inraw[i+j], d_samples_per_chip) > bit_energy(&inraw[i+j+d_samples_per_chip], d_samples_per_chip)) ? bit_energy(&inraw[i+j], d_samples_per_chip) : bit_energy(&inraw[i+j+d_samples_per_chip], d_samples_per_chip);
 			if(t_max < (reference_level / 2)) packet_attrib = Short_Packet;
 		}
 

src/lib/air_modes_preamble.cc

@@ -39,7 +39,7 @@ int air_modes_preamble::work(int noutput_items,
 
 	int size = noutput_items - d_check_width;
 	int pulse_offsets[4];
-	int bit_energies[4];
+	float bit_energies[4];
 
 	for(int i = d_samples_per_chip; i < size; i++) {
 		float pulse_threshold = bit_energy(&inavg[i], d_samples_per_chip) * d_threshold;

src/lib/air_modes_slicer.cc

@@ -90,7 +90,7 @@ int air_modes_slicer::work(int noutput_items,
 //				confidence = bool(int(firstchip_inref) + int(secondchip_inref)); //one and only one chip in the reference zone
 
 				//below is the Lincoln Labs slicer. it may produce greater bit errors. supposedly it is more resistant to mode A/C FRUIT.
-
+        //see http://adsb.tc.faa.gov/WG3_Meetings/Meeting8/Squitter-Lon.pdf
 				if(firstchip_inref && !secondchip_inref) {
 					slice = 1;
 					confidence = 1;

src/python/altitude.py

@@ -3,6 +3,7 @@
 
 #betcha this would be faster if you used a table for mode C
 #you could strip out D1 since it's never used, that leaves 11 bits (table is 2048 entries)
+#on the other hand doing it this way is educational for others
 def decode_alt(alt, bit13):
 	if alt & 0x40 and bit13 is True:
 		return "METRIC ERROR"

src/python/cpr.py

@@ -2,12 +2,15 @@
 #from string import split, join
 #from math import pi, floor, cos, acos
 import math, time
-#this implements CPR position decoding. local only for now.
+#this implements CPR position decoding.
 
 latz = 15
 nbits = 17
-my_lat = 37.76225 #update these later!
-my_lon = -122.44254
+#my_lat = 37.76225 #update these later!
+#my_lon = -122.44254
+#ER
+my_lat = 37.40889176297184
+my_lon = -122.07765340805054
 
 
 def nz(ctype):
@@ -229,8 +232,8 @@ def range_bearing(loc_a, loc_b):
 
 	avg_lat = (a_lat + b_lat) / 2.0
 
-	R1 = earth_radius_mi*(1.0-esquared)/pow((1.0-esquared*pow(math.sin(avg_lat),2)),1.5)
-             
+	R1 = earth_radius_mi*(1.0-esquared)/pow((1.0-esquared*pow(math.sin(avg_lat),2)),1.5)
+             
 	R2 = earth_radius_mi/math.sqrt(1.0-esquared*pow(math.sin(avg_lat),2))
 
 	distance_North = R1*delta_lat

src/python/modes_print.py

@@ -33,7 +33,7 @@ def modes_print(message):
 	else:
 		output = "No handler for message type " + str(msgtype) + " from " + str(ecc)
 
-	output = "(%.0f) " % float(reference) + output
+	output = "(%.0f) " % (10.0*math.log10(float(reference))) + output
 
 	return output
 

src/python/uhd_modes.py

@@ -33,7 +33,7 @@ The following are optional command line parameters:
 -R SUBDEV    Daughter board specification, defaults to first found
 -f FREQ      USRP receive frequency (1090 MHz Default)
 -g GAIN      Daughterboard gain setting. Defaults to mid-range.
--d DECIM     USRP decimation rate
+-r RATE      USRP sample rate
 -t THRESH    Receiver valid pulse threshold
 -a           Output all frames. Defaults only output frames
 
@@ -80,7 +80,6 @@ class adsb_rx_block (gr.top_block):
 		if options.output_all :
 			pass_all = 1
 
-		self.gain = gr.multiply_const_cc(1000000)
 		self.demod = gr.complex_to_mag()
 		self.avg = gr.moving_average_ff(100, 1.0/100, 400);
 		self.preamble = air.modes_preamble(rate, options.threshold)
@@ -95,7 +94,7 @@ class adsb_rx_block (gr.top_block):
 #		else:
 		self.filt = self.u
 
-		self.connect(self.filt, self.gain, self.demod)
+		self.connect(self.filt, self.demod)
 		self.connect(self.demod, self.avg)
 		self.connect(self.demod, (self.preamble, 0))
 		self.connect(self.avg, (self.preamble, 1))