initial commit

ADSBLowLevelEncoder.py

@@ -0,0 +1,102 @@
+from CustomDecorators import *
+import numpy
+
+@Singleton
+class ADSBLowLevelEncoder:
+    """
+    Hamming and Manchester Encoding example
+
+    Author: Joel Addison
+    Date: March 2013
+
+    Functions to do (7,4) hamming encoding and decoding, including error detection
+    and correction.
+    Manchester encoding and decoding is also included, and by default will use
+    least bit ordering for the byte that is to be included in the array.
+    """
+
+    def __init__(self):
+        self.adsb_frame_preamble = [0xA1,0x40]
+        self.adsb_frame_pause = [0]*70
+###############################################################
+# Further work on fork
+# Copyright (C) 2017 David Robinson
+    def extract_bit(self, byte, pos):
+        """
+        Extract a bit from a given byte using MS ordering.
+        ie. B7 B6 B5 B4 B3 B2 B1 B0
+        """
+        return (byte >> pos) & 0x01
+
+    def manchester_encode(self, byte):
+        """
+        Encode a byte using Manchester encoding. Returns an array of bits.
+        Adds two start bits (1, 1) and one stop bit (0) to the array.
+        """
+        manchester_encoded = []
+
+        # Encode byte
+        for i in range(7, -1, -1):
+            if self.extract_bit(byte, i):
+                manchester_encoded.extend([0,1])
+            else:
+                manchester_encoded.extend([1,0])
+
+        return manchester_encoded
+
+    def frame_1090es_ppm_modulate(self, even, odd = []):
+        """
+        Args:
+            even and odd: The data frames that need to be converted to PPM
+        Returns:
+            The bytearray of the PPM data
+        """
+        ppm = [ ]
+
+        length_even = len(even)
+        length_odd  = len(odd)
+
+        if (length_even != 0):
+            ppm.extend(self.adsb_frame_pause)      # pause
+            ppm.extend(self.adsb_frame_preamble)   # preamble
+            
+            for i in range(length_even):
+                word16 = numpy.packbits(self.manchester_encode(~even[i]))
+                ppm.extend(word16[0:2])
+            
+            ppm.extend(self.adsb_frame_pause)  # pause
+
+        if (length_odd != 0):
+            ppm.extend(self.adsb_frame_pause)        # pause
+            ppm.extend(self.adsb_frame_preamble)     # preamble
+
+            for i in range(length_odd):
+                word16 = numpy.packbits(self.manchester_encode(~odd[i]))
+                ppm.extend(word16[0:2])
+
+            ppm.extend(self.adsb_frame_pause)  # pause
+        
+        return bytearray(ppm)
+
+    def hackrf_raw_IQ_format(self, ppm):
+        """
+        Args:
+            ppm: this is some data in ppm (pulse position modulation) which will be converted into
+                 hackRF raw IQ sample format, ready to be broadcasted
+            
+        Returns:
+            bytearray: containing the IQ data
+        """
+        signal = []
+        bits = numpy.unpackbits(numpy.asarray(ppm, dtype=numpy.uint8))
+        for bit in bits:
+            if bit == 1:
+                I = 127
+                Q = 127
+            else:
+                I = 0
+                Q = 0
+            signal.append(I)
+            signal.append(Q)
+
+        return bytearray(signal)