--- /dev/null
+/*
+ * 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 3, 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_sync.h>
+#include <pageri_flex_modes.h>
+#include <pageri_bch3221.h>
+#include <pageri_util.h>
+#include <gr_io_signature.h>
+#include <gr_count_bits.h>
+#include <cstdio>
+
+pager_flex_sync_sptr pager_make_flex_sync()
+{
+ return pager_flex_sync_sptr(new pager_flex_sync());
+}
+
+// FLEX sync block takes input from sliced baseband stream [0-3] at specified
+// channel rate. Symbol timing is established based on receiving one of the
+// defined FLEX protocol synchronization words. The block outputs one FLEX frame
+// worth of bits on each output phase for the data portion of the frame. Unused phases
+// get all zeros, which are considered idle code words.
+
+pager_flex_sync::pager_flex_sync() :
+ gr_block ("flex_sync",
+ gr_make_io_signature (1, 1, sizeof(unsigned char)),
+ gr_make_io_signature (4, 4, sizeof(unsigned char))),
+ d_sync(10) // Fixed at 10 samples per baud (@ 1600 baud)
+{
+ enter_idle();
+}
+
+void pager_flex_sync::forecast(int noutput_items, gr_vector_int &inputs_required)
+{
+ // samples per bit X number of outputs needed
+ int items = noutput_items*d_spb;
+ for (unsigned int i = 0; i < inputs_required.size(); i++)
+ inputs_required[i] = items;
+}
+
+int pager_flex_sync::index_avg(int start, int end)
+{
+ // modulo average
+ if (start < end)
+ return (end + start)/2;
+ else
+ return ((end + start)/2 + d_spb/2) % d_spb;
+}
+
+bool pager_flex_sync::test_sync(unsigned char sym)
+{
+ // 64-bit FLEX sync code:
+ // AAAA:BBBBBBBB:CCCC
+ //
+ // Where BBBBBBBB is always 0xA6C6AAAA
+ // and AAAA^CCCC is 0xFFFF
+ //
+ // Specific values of AAAA determine what bps and encoding the
+ // packet is beyond the frame information word
+ //
+ // First we match on the marker field with a hamming distance < 4
+ // Then we match on the outer code with a hamming distance < 4
+
+ d_sync[d_index] = (d_sync[d_index] << 1) | (sym < 2);
+ gr_int64 val = d_sync[d_index];
+ gr_int32 marker = ((val & 0x0000FFFFFFFF0000ULL)) >> 16;
+
+ if (gr_count_bits32(marker^FLEX_SYNC_MARKER) < 4) {
+ gr_int32 code = ((val & 0xFFFF000000000000ULL) >> 32) |
+ (val & 0x000000000000FFFFULL);
+
+ for (int i = 0; i < num_flex_modes; i++) {
+ if (gr_count_bits32(code^flex_modes[i].sync) < 4) {
+ d_mode = i;
+ return true;
+ }
+ }
+
+ // Marker received but doesn't match known codes
+ // All codes have high word inverted to low word
+ unsigned short high = (code & 0xFFFF0000) >> 16;
+ unsigned short low = code & 0x0000FFFF;
+ unsigned short syn = high^low;
+ if (syn == 0xFFFF)
+ fprintf(stderr, "Unknown sync code detected: %08X\n", code);
+ }
+
+ return false;
+}
+
+void pager_flex_sync::enter_idle()
+{
+ d_state = ST_IDLE;
+ d_index = 0;
+ d_start = 0;
+ d_center = 0;
+ d_end = 0;
+ d_count = 0;
+ d_mode = 0;
+ d_baudrate = 1600;
+ d_levels = 2;
+ d_spb = 16000/d_baudrate;
+ d_bit_a = 0;
+ d_bit_b = 0;
+ d_bit_c = 0;
+ d_bit_d = 0;
+ d_hibit = false;
+ fflush(stdout);
+}
+
+void pager_flex_sync::enter_syncing()
+{
+ d_start = d_index;
+ d_state = ST_SYNCING;
+}
+
+void pager_flex_sync::enter_sync1()
+{
+ d_state = ST_SYNC1;
+ d_end = d_index;
+ d_center = index_avg(d_start, d_end); // Center of goodness
+ d_count = 0;
+}
+
+void pager_flex_sync::enter_sync2()
+{
+ d_state = ST_SYNC2;
+ d_count = 0;
+ d_baudrate = flex_modes[d_mode].baud;
+ d_levels = flex_modes[d_mode].levels;
+ d_spb = 16000/d_baudrate;
+
+ if (d_baudrate == 3200) {
+ // Oversampling buffer just got halved
+ d_center = d_center/2;
+
+ // We're here at the center of a 1600 baud bit
+ // So this hack puts the index and bit counter
+ // in the right place for 3200 bps.
+ d_index = d_index/2-d_spb/2;
+ d_count = -1;
+ }
+}
+
+void pager_flex_sync::enter_data()
+{
+ d_state = ST_DATA;
+ d_count = 0;
+}
+
+void pager_flex_sync::parse_fiw()
+{
+ // Nothing is done with these now, but these will end up getting
+ // passed as metadata when mblocks are available
+
+ // Bits 31-28 are frame number related, but unknown function
+ // This might be a checksum
+ d_unknown2 = pageri_reverse_bits8((d_fiw >> 24) & 0xF0);
+
+ // Cycle is bits 27-24, reversed
+ d_cycle = pageri_reverse_bits8((d_fiw >> 20) & 0xF0);
+
+ // Frame is bits 23-17, reversed
+ d_frame = pageri_reverse_bits8((d_fiw >> 16) & 0xFE);
+
+ // Bits 16-11 are some sort of marker, usually identical across
+ // many frames but sometimes changes between frames or modes
+ d_unknown1 = (d_fiw >> 11) & 0x3F;
+
+ //printf("CYC:%02i FRM:%03i\n", d_cycle, d_frame);
+}
+
+int pager_flex_sync::output_symbol(unsigned char sym)
+{
+ // Here is where we output a 1 or 0 on each phase according
+ // to current FLEX mode and symbol value. Unassigned phases
+ // are zero from the enter_idle() initialization.
+ //
+ // FLEX can transmit the data portion of the frame at either
+ // 1600 bps or 3200 bps, and can use either two- or four-level
+ // FSK encoding.
+ //
+ // At 1600 bps, 2-level, a single "phase" is transmitted with bit
+ // value '0' using level '3' and bit value '1' using level '0'.
+ //
+ // At 1600 bps, 4-level, a second "phase" is transmitted, and the
+ // di-bits are encoded with a gray code:
+ //
+ // Symbol Phase 1 Phase 2
+ // ------ ------- -------
+ // 0 1 1
+ // 1 1 0
+ // 2 0 0
+ // 3 0 1
+ //
+ // At 1600 bps, 4-level, these are called PHASE A and PHASE B.
+ //
+ // At 3200 bps, the same 1 or 2 bit encoding occurs, except that
+ // additionally two streams are interleaved on alternating symbols.
+ // Thus, PHASE A (and PHASE B if 4-level) are decoded on one symbol,
+ // then PHASE C (and PHASE D if 4-level) are decoded on the next.
+
+ int bits = 0;
+
+ if (d_baudrate == 1600) {
+ d_bit_a = (sym < 2);
+ if (d_levels == 4)
+ d_bit_b = (sym == 0) || (sym == 3);
+
+ *d_phase_a++ = d_bit_a;
+ *d_phase_b++ = d_bit_b;
+ *d_phase_c++ = d_bit_c;
+ *d_phase_d++ = d_bit_d;
+ bits++;
+ }
+ else {
+ if (!d_hibit) {
+ d_bit_a = (sym < 2);
+ if (d_levels == 4)
+ d_bit_b = (sym == 0) || (sym == 3);
+ d_hibit = true;
+ }
+ else {
+ d_bit_c = (sym < 2);
+ if (d_levels == 4)
+ d_bit_d = (sym == 0) || (sym == 3);
+ d_hibit = false;
+
+ *d_phase_a++ = d_bit_a;
+ *d_phase_b++ = d_bit_b;
+ *d_phase_c++ = d_bit_c;
+ *d_phase_d++ = d_bit_d;
+ bits++;
+ }
+ }
+
+ return bits;
+}
+
+int pager_flex_sync::general_work(int noutput_items,
+ gr_vector_int &ninput_items,
+ gr_vector_const_void_star &input_items,
+ gr_vector_void_star &output_items)
+{
+ const unsigned char *in = (const unsigned char *)input_items[0];
+ d_phase_a = (unsigned char *)output_items[0];
+ d_phase_b = (unsigned char *)output_items[1];
+ d_phase_c = (unsigned char *)output_items[2];
+ d_phase_d = (unsigned char *)output_items[3];
+
+ int i = 0, j = 0;
+ int ninputs = ninput_items[0];
+
+ while (i < ninputs && j < noutput_items) {
+ unsigned char sym = *in++; i++;
+ d_index = ++d_index % d_spb;
+
+ switch (d_state) {
+ case ST_IDLE:
+ // Continually compare the received symbol stream
+ // against the known FLEX sync words.
+ if (test_sync(sym))
+ enter_syncing();
+ break;
+
+ case ST_SYNCING:
+ // Wait until we stop seeing sync, then calculate
+ // the center of the bit period (d_center)
+ if (!test_sync(sym))
+ enter_sync1();
+ break;
+
+ case ST_SYNC1:
+ // Skip 16 bits of dotting, then accumulate 32 bits
+ // of Frame Information Word.
+ if (d_index == d_center) {
+ d_fiw = (d_fiw << 1) | (sym > 1);
+ if (++d_count == 48) {
+ // FIW is accumulated, call BCH to error correct it
+ pageri_bch3221(d_fiw);
+ parse_fiw();
+ enter_sync2();
+ }
+ }
+ break;
+
+ case ST_SYNC2:
+ // This part and the remainder of the frame are transmitted
+ // at either 1600 bps or 3200 bps based on the received
+ // FLEX sync word. The second SYNC header is 25ms of idle bits
+ // at either speed.
+ if (d_index == d_center) {
+ // Skip 25 ms = 40 bits @ 1600 bps, 80 @ 3200 bps
+ if (++d_count == d_baudrate/40)
+ enter_data();
+ }
+ break;
+
+ case ST_DATA:
+ // The data portion of the frame is 1760 ms long at either
+ // baudrate. This is 2816 bits @ 1600 bps and 5632 bits @ 3200 bps.
+ // The output_symbol() routine decodes and doles out the bits
+ // to each of the four transmitted phases of FLEX interleaved codes.
+ if (d_index == d_center) {
+ j += output_symbol(sym);
+ if (++d_count == d_baudrate*1760/1000)
+ enter_idle();
+ }
+ break;
+
+ default:
+ assert(0); // memory corruption of d_state if ever gets here
+ break;
+ }
+ }
+
+ consume_each(i);
+ return j;
+}
projects / debian / gnuradio / blobdiff