Substantial Work on the Encoder
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Cort Buffington
parent
62e791a958
commit
fc1139aa2f
137
bptc19696.py
137
bptc19696.py
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@ -18,9 +18,7 @@ __license__ = 'Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unpo
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__maintainer__ = 'Cort Buffington, N0MJS'
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__email__ = 'n0mjs@me.com'
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#------------------------------------------------------------------------------
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# BPTC(196,96) Decoding routings
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#------------------------------------------------------------------------------
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# Interleaer index
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INDEX_181 = (
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0, 181, 166, 151, 136, 121, 106, 91, 76, 61, 46, 31, 16, 1, 182, 167, 152, 137,
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@ -35,20 +33,25 @@ INDEX_181 = (
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73, 58, 43, 28, 13, 194, 179, 164, 149, 134, 119, 104, 89, 74, 59, 44, 29, 14,
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195, 180, 165, 150, 135, 120, 105, 90, 75, 60, 45, 30, 15)
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# Converts a DMR frame using 98-68-98 (info-sync/EMB-info) into 196 bit array
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def to_binary_19696(_data):
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_bits = bitarray(endian='big')
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_bits.frombytes(_data)
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return _bits[:98] + _bits[-98:]
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#------------------------------------------------------------------------------
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# BPTC(196,96) Decoding Routings
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#------------------------------------------------------------------------------
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# Converts a DMR frame using 98-68-98 (info-sync/EMB-info) into 196 bit array
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# Applies interleave indecies de-interleave 196 bit array
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def deinterleave_19696(_data):
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_bits = bitarray(endian='big')
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_bits.frombytes(_data)
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for i in xrange(68):
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_bits.pop(98)
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deint = bitarray(196, endian='big')
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for index in xrange(196):
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deint[index] = _data[INDEX_181[index]] # the real math is slower: deint[index] = _data[(index * 181) % 196]
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deint[index] = _bits[INDEX_181[index]] # the real math is slower: deint[index] = _data[(index * 181) % 196]
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return deint
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# Applies BTPC error detection/correction routines (INCOMPLETE)
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# Applies BTPC error detection/correction routines
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# This routine, in practice, will not be used in HBlink or DMRlink - it's only usefull for OTA direct data
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def error_check_19696(_data):
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count = 0
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column = bitarray(13, endian='big')
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@ -68,7 +71,6 @@ def error_check_19696(_data):
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_data[pos] = result_1393[0][index]
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pos += 15
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errors = True
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print('fixing error in column {}'.format(col))
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for index in xrange(9):
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pos = (index*15) + 1
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@ -76,10 +78,8 @@ def error_check_19696(_data):
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if result_15113[1]:
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errors = True
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_data[pos:(pos+15)] = result_15113[0]
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print('fixing error in row {}'.format(index))
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count += 1
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print('pass count is {}'.format(count))
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if not errors or count > 4: break
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return (errors)
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@ -90,9 +90,54 @@ def to_bytes_19696(_data):
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#------------------------------------------------------------------------------
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# BPTC(196,96) Decoding routings
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# BPTC(196,96) Encoding Routings
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#------------------------------------------------------------------------------
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# not yet implemented
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def interleave_19696(_data):
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inter = bitarray(196, endian='big')
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for index in xrange(196):
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inter[INDEX_181[index]] = _data[index] # the real math is slower: deint[index] = _data[(index * 181) % 196]
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return inter
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# Accepts 12 byte LC header + RS1293, converts to binary and pads for 196 bit
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# encode hamming 15113 to rows and 1393 to columns
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def enc_bptc_19696(_data):
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# Create a bitarray from the 4 bytes of LC data (includes RS1293 ECC)
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_bdata = bitarray(endian='big')
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_bdata.frombytes(_data)
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# Insert R0-R3 bits
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for i in xrange(4):
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_bdata.insert(0, 0)
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# Get row hamming 15,11,3 and append. +1 is to account for R3 that makes an even 196bit string
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for index in xrange(9):
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spos = (index*15) + 1
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epos= spos + 11
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_rowp = hamming.enc_15113(_bdata[spos:epos])
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for pbit in xrange(4):
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_bdata.insert(epos+pbit,_rowp[pbit])
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# Get column hamming 13,9,3 and append. +1 is to account for R3 that makes an even 196bit string
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# Pad out the bitarray to a full 196 bits. Can't insert into 'columns'
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for i in xrange(60):
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_bdata.append(0)
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column = bitarray(9, endian='big') # Temporary bitarray to hold column data
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for col in xrange(15):
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spos = col + 1
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for index in xrange(9):
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column[index] = _bdata[spos]
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spos += 15
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_colp = hamming.enc_1393(column)
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# Insert bits into matrix...
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cpar = 136 + col # Starting location in the matrix for column bits
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for pbit in xrange(4):
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_bdata[cpar] = _colp[pbit]
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cpar += 15
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return _bdata
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#------------------------------------------------------------------------------
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@ -105,37 +150,45 @@ if __name__ == '__main__':
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from time import time
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# Validation Example
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# Good Data
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data = '\x2b\x60\x04\x10\x1f\x84\x2d\xd0\x0d\xf0\x7d\x41\x04\x6d\xff\x57\xd7\x5d\xf5\xde\x30\x15\x2e\x20\x70\xb2\x0f\x80\x3f\x88\xc6\x95\xe2'
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# Bad Data
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data = '\xff\xff\x14\x10\x1f\x84\x2d\xd0\x0d\xf0\x7d\x41\x04\x6d\xff\x57\xd7\x5d\xf5\xde\x30\x15\x2e\x20\x70\xb2\x0f\x80\x3f\x88\xc6\x95\xe2'
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orig_data = '\x00\x10\x20\x00\x0c\x30\x2f\x9b\xe5\xda\xd4\x5a'
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t0 = time()
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bin_data = to_binary_19696(data)
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deint_data = deinterleave_19696(bin_data)
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enc_data = enc_bptc_19696(orig_data)
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inter_data = interleave_19696(enc_data)
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t1 = time()
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encode_time = t1-t0
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# Good Data
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dec_data = '\x2b\x60\x04\x10\x1f\x84\x2d\xd0\x0d\xf0\x7d\x41\x04\x6d\xff\x57\xd7\x5d\xf5\xde\x30\x15\x2e\x20\x70\xb2\x0f\x80\x3f\x88\xc6\x95\xe2'
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# Bad Data
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#dec_data = '\x2b\x60\xff\xff\xff\x85\x2d\xd0\x0d\xf0\x7d\x41\x04\x6d\xff\x57\xd7\x5d\xf5\xde\x30\x15\x2e\x20\x70\xb2\x0f\x80\x3f\x88\xc6\x95\xe2'
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t0 = time()
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#bin_data = dec_to_binary_19696(dec_data)
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deint_data = deinterleave_19696(dec_data)
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err_corrected = error_check_19696(deint_data) # This corrects deint_data in place -- it does not return a new array!!!
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if err_corrected:
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print('WARNING DATA COULD NOT BE CORRECTED')
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ext_data = to_bytes_19696(deint_data)
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t1 = time()
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print('TIME: ', t1-t0, '\n')
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decode_time = t1-t0
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print('original 33 byte data block:')
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print(h(data))
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print(len(data), 'bytes')
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print('VALIDATION ROUTINE:')
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print()
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print('ENCODER TEST:')
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print('Original Data: {}, {} bytes'.format(h(orig_data), len(orig_data)))
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print('Encoding time: {} seconds'.format(encode_time))
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print('Encoded data: {}, {} bits'.format(enc_data, len(enc_data)))
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print()
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print('DECODER TEST:')
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print('Encoded data: {}, {} bytes'.format(h(dec_data), len(dec_data)))
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print('Decoding Time: {} seconds'.format(t1-t0))
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if err_corrected:
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print('WARNING DATA COULD NOT BE CORRECTED')
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else:
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print('Decoded Data: {}, {} bytes'.format(h(ext_data), len(ext_data)))
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print()
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print('binary data (discarding sync)')
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print(len(bin_data), 'bits')
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print(bin_data)
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print()
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print('deinterleaved binary data')
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print(len(deint_data), 'bits')
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print(deint_data)
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print(h(deint_data.tobytes()))
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print()
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print('decoded hex data should be: 001020000c302f9be5dad45a')
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print('decoded data is: ', h(ext_data))
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print(len(ext_data), 'bytes')
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print('ENCODED vs. DECODED:')
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print('enc:', enc_data)
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print('dec:', deint_data)
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print(enc_data == deint_data)
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