From 475bc5da838c1395af499b2230e2b4565aba99c2 Mon Sep 17 00:00:00 2001
From: nzkarit <nzkarit@users.noreply.github.com>
Date: Thu, 7 Sep 2017 18:59:24 +1200
Subject: [PATCH] Comments on what things are doing and also doing the DD step
 in the script

---
 ADSB_Encoder.py | 14 ++++++++------
 HackRF.py       |  2 +-
 location.py     |  6 ++++++
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/ADSB_Encoder.py b/ADSB_Encoder.py
index 3c6bb3e..597499e 100755
--- a/ADSB_Encoder.py
+++ b/ADSB_Encoder.py
@@ -6,6 +6,7 @@ from location import *
 from conversions import *
 from parity import *
 from HackRF import HackRF
+import os
 
 ###############################################################
 
@@ -29,7 +30,7 @@ import numpy
 
 def df17_pos_rep_encode(ca, icao, tc, ss, nicsb, alt, time, lat, lon, surface):
 
-    format = 17
+    format = 17 #The format type of an ADSB message
 
     enc_alt =	encode_alt_modes(alt, surface)
     #print "Alt(%r): %X " % (surface, enc_alt)
@@ -141,10 +142,10 @@ if __name__ == "__main__":
     lon = float(argv[3])
     alt = float(argv[4])
 
-    ca = 5
-    tc = 11
-    ss = 0
-    nicsb = 0    
+    ca = 5 # Capability 
+    tc = 11 # Type Code see: https://adsb-decode-guide.readthedocs.io/en/latest/content/introduction.html#ads-b-message-types
+    ss = 0 # Surveillance status
+    nicsb = 0 # NIC supplement-B
     time = 0       
     surface = False
 
@@ -161,5 +162,6 @@ if __name__ == "__main__":
     hackrf = HackRF()
     samples_array = hackrf.hackrf_raw_IQ_format(df17_array)
 
-    SamplesFile = open("Samples.iq8s", "wb")
+    SamplesFile = open("Samples.iq8s", "wb") # TODO make this a function and take the file name. Also have the option to run dd on it.
     SamplesFile.write(samples_array)
+    os.system("dd if=Samples.iq8s of=Samples_256K.iq8s bs=4k seek=63") # TODO make this a flag, also make it take the file name
diff --git a/HackRF.py b/HackRF.py
index 70a2ebe..8e97f26 100644
--- a/HackRF.py
+++ b/HackRF.py
@@ -11,7 +11,7 @@ class HackRF:
             ppm: this is some data in ppm (pulse position modulation) which you want to convert into raw IQ format
             
         Returns:
-            bytearray containig the IQ data
+            bytearray: containing the IQ data
         """
 
         signal = []
diff --git a/location.py b/location.py
index b6068b7..71d7e83 100644
--- a/location.py
+++ b/location.py
@@ -40,6 +40,10 @@ def encode_alt_modes(alt, bit13):
 latz = 15
 
 def nz(ctype):
+	"""
+	Number of geographic latitude zones between equator and a pole. It is set to NZ = 15 for Mode-S CPR encoding
+	https://adsb-decode-guide.readthedocs.io/en/latest/content/cpr.html
+	"""
 	return 4 * latz - ctype
 
 def dlat(ctype, surface):
@@ -68,6 +72,8 @@ def dlon(declat_in, ctype, surface):
 	return tmp / nlcalc
 
 #encode CPR position
+# https://adsb-decode-guide.readthedocs.io/en/latest/content/cpr.html
+# compact position reporting
 def cpr_encode(lat, lon, ctype, surface):
     if surface is True:
         scalar = 2.**19