2 * Copyright 2004,2006 Free Software Foundation, Inc.
4 * This file is part of GNU Radio
6 * GNU Radio is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 3, or (at your option)
11 * GNU Radio is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with GNU Radio; see the file COPYING. If not, write to
18 * the Free Software Foundation, Inc., 51 Franklin Street,
19 * Boston, MA 02110-1301, USA.
26 #include <pager_flex_deinterleave.h>
27 #include <pageri_bch3221.h>
28 #include <pageri_util.h>
29 #include <gr_io_signature.h>
31 pager_flex_deinterleave_sptr pager_make_flex_deinterleave()
33 return pager_flex_deinterleave_sptr(new pager_flex_deinterleave());
36 pager_flex_deinterleave::pager_flex_deinterleave() :
37 gr_sync_decimator("flex_deinterleave",
38 gr_make_io_signature(1, 1, sizeof(unsigned char)),
39 gr_make_io_signature(1, 1, sizeof(gr_int32)), 32)
41 set_output_multiple(8); // One FLEX block at a time
44 int pager_flex_deinterleave::work(int noutput_items,
45 gr_vector_const_void_star &input_items,
46 gr_vector_void_star &output_items)
48 const unsigned char *in = (const unsigned char *)input_items[0];
49 gr_int32 *out = (gr_int32 *)output_items[0];
51 // FLEX codewords are interleaved in blocks of 256 bits or 8, 32 bit
52 // codes. To deinterleave we parcel each incoming bit into the MSB
53 // of each codeword, then switch to MSB-1, etc. This is done by shifting
54 // in the bits from the right on each codeword as the bits come in.
55 // When we are done we have a FLEX block of eight codewords, ready for
56 // conversion to data words.
58 // FLEX data words are recovered by reversing the bit order of the code
59 // word, masking off the (reversed) ECC, and inverting the remainder of
62 // The data portion of a FLEX frame consists of 11 of these deinterleaved
63 // and converted blocks.
65 // set_output_multiple garauntees we have output space for at least
66 // eight data words, and 256 bits are supplied on input
69 for (i = 0; i < 32; i++) {
70 for (j = 0; j < 8; j++) {
72 d_codewords[j] |= *in++;
76 // Now convert code words into data words
77 for (j = 0; j < 8; j++) {
78 gr_int32 codeword = d_codewords[j];
80 // Apply BCH 32,21 error correction
81 // TODO: mark dataword when codeword fails ECC
82 pageri_bch3221(codeword);
85 codeword = pageri_reverse_bits32(codeword);
87 // Mask off ECC then invert lower 21 bits
88 codeword = (codeword & 0x001FFFFF)^0x001FFFFF;