1 files changed, 94 insertions, 0 deletions
diff --git a/gr-pager/src/pager_flex_deinterleave.cc b/gr-pager/src/pager_flex_deinterleave.cc
new file mode 100644
index 000000000..e689e9f39
--- /dev/null
+++ b/gr-pager/src/pager_flex_deinterleave.cc
@@ -0,0 +1,94 @@
+/*
+ * Copyright 2004,2006 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <pager_flex_deinterleave.h>
+#include <pageri_bch3221.h>
+#include <pageri_util.h>
+#include <gr_io_signature.h>
+
+pager_flex_deinterleave_sptr pager_make_flex_deinterleave()
+{
+    return pager_flex_deinterleave_sptr(new pager_flex_deinterleave());
+}
+
+pager_flex_deinterleave::pager_flex_deinterleave() :
+    gr_sync_decimator("flex_deinterleave",
+    gr_make_io_signature(1, 1, sizeof(unsigned char)),
+    gr_make_io_signature(1, 1, sizeof(gr_int32)), 32)
+{
+    set_output_multiple(8); // One FLEX block at a time
+}
+
+int pager_flex_deinterleave::work(int noutput_items,
+    gr_vector_const_void_star &input_items,
+    gr_vector_void_star &output_items)
+{
+    const unsigned char *in = (const unsigned char *)input_items[0];
+    gr_int32 *out = (gr_int32 *)output_items[0];    
+
+    // FLEX codewords are interleaved in blocks of 256 bits or 8, 32 bit
+    // codes.  To deinterleave we parcel each incoming bit into the MSB
+    // of each codeword, then switch to MSB-1, etc.  This is done by shifting
+    // in the bits from the right on each codeword as the bits come in.
+    // When we are done we have a FLEX block of eight codewords, ready for
+    // conversion to data words.
+    //
+    // FLEX data words are recovered by reversing the bit order of the code
+    // word, masking off the (reversed) ECC, and inverting the remainder of 
+    // the bits (!).
+    //
+    // The data portion of a FLEX frame consists of 11 of these deinterleaved
+    // and converted blocks.
+    //
+    // set_output_multiple garauntees we have output space for at least
+    // eight data words, and 256 bits are supplied on input
+
+    int i, j;
+    for (i = 0; i < 32; i++) {
+	for (j = 0; j < 8; j++) {
+	    d_codewords[j] <<= 1;
+	    d_codewords[j]  |= *in++;
+	}
+    }
+
+    // Now convert code words into data words  
+    for (j = 0; j < 8; j++) {
+	gr_int32 codeword = d_codewords[j];
+	
+	// Apply BCH 32,21 error correction
+	// TODO: mark dataword when codeword fails ECC
+	pageri_bch3221(codeword);
+	
+	// Reverse bit order
+	codeword = pageri_reverse_bits32(codeword);
+
+	// Mask off ECC then invert lower 21 bits
+	codeword = (codeword & 0x001FFFFF)^0x001FFFFF;
+
+	*out++ = codeword;
+    }
+    
+    return j;
+}