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+/* -*- c++ -*- */
+/*
+ * Copyright 2007,2008,2010-2012 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 "ofdm_sampler_impl.h"
+#include <gr_io_signature.h>
+#include <gr_expj.h>
+#include <cstdio>
+
+namespace gr {
+ namespace digital {
+
+ ofdm_sampler::sptr
+ ofdm_sampler::make(unsigned int fft_length,
+ unsigned int symbol_length,
+ unsigned int timeout)
+ {
+ return gnuradio::get_initial_sptr
+ (new ofdm_sampler_impl(fft_length, symbol_length, timeout));
+ }
+
+ ofdm_sampler_impl::ofdm_sampler_impl(unsigned int fft_length,
+ unsigned int symbol_length,
+ unsigned int timeout)
+ : gr_block("ofdm_sampler",
+ gr_make_io_signature2(2, 2, sizeof(gr_complex), sizeof(char)),
+ gr_make_io_signature2(2, 2, sizeof(gr_complex)*fft_length, sizeof(char)*fft_length)),
+ d_state(STATE_NO_SIG), d_timeout_max(timeout),
+ d_fft_length(fft_length), d_symbol_length(symbol_length)
+ {
+ set_relative_rate(1.0/(double) fft_length); // buffer allocator hint
+ }
+
+ ofdm_sampler_impl::~ofdm_sampler_impl()
+ {
+ }
+
+ void
+ ofdm_sampler_impl::forecast(int noutput_items, gr_vector_int &ninput_items_required)
+ {
+ // FIXME do we need more
+ //int nreqd = (noutput_items-1) * d_symbol_length + d_fft_length;
+ int nreqd = d_symbol_length + d_fft_length;
+ unsigned ninputs = ninput_items_required.size();
+ for(unsigned i = 0; i < ninputs; i++)
+ ninput_items_required[i] = nreqd;
+ }
+
+ int
+ ofdm_sampler_impl::general_work(int noutput_items,
+ gr_vector_int &ninput_items,
+ gr_vector_const_void_star &input_items,
+ gr_vector_void_star &output_items)
+ {
+ const gr_complex *iptr = (const gr_complex*)input_items[0];
+ const char *trigger = (const char*)input_items[1];
+
+ gr_complex *optr = (gr_complex*)output_items[0];
+ char *outsig = (char*)output_items[1];
+
+ //FIXME: we only process a single OFDM symbol at a time; after the preamble, we can
+ // process a few at a time as long as we always look out for the next preamble.
+
+ unsigned int index = d_fft_length; // start one fft length into the input so we can always look back this far
+
+ outsig[0] = 0; // set output to no signal by default
+
+ // Search for a preamble trigger signal during the next symbol length
+ while((d_state != STATE_PREAMBLE) && (index <= (d_symbol_length+d_fft_length))) {
+ if(trigger[index]) {
+ outsig[0] = 1; // tell the next block there is a preamble coming
+ d_state = STATE_PREAMBLE;
+ }
+ else
+ index++;
+ }
+
+ unsigned int i, pos, ret;
+ switch(d_state) {
+ case(STATE_PREAMBLE):
+ // When we found a preamble trigger, get it and set the symbol boundary here
+ for(i = (index - d_fft_length + 1); i <= index; i++) {
+ *optr++ = iptr[i];
+ }
+
+ d_timeout = d_timeout_max; // tell the system to expect at least this many symbols for a frame
+ d_state = STATE_FRAME;
+ consume_each(index - d_fft_length + 1); // consume up to one fft_length away to keep the history
+ ret = 1;
+ break;
+
+ case(STATE_FRAME):
+ // use this state when we have processed a preamble and are getting the rest of the frames
+ //FIXME: we could also have a power squelch system here to enter STATE_NO_SIG if no power is received
+
+ // skip over fft length history and cyclic prefix
+ pos = d_symbol_length; // keeps track of where we are in the input buffer
+ while(pos < d_symbol_length + d_fft_length) {
+ *optr++ = iptr[pos++];
+ }
+
+ if(d_timeout-- == 0) {
+ printf("TIMEOUT\n");
+ d_state = STATE_NO_SIG;
+ }
+
+ consume_each(d_symbol_length); // jump up by 1 fft length and the cyclic prefix length
+ ret = 1;
+ break;
+
+ case(STATE_NO_SIG):
+ default:
+ consume_each(index-d_fft_length); // consume everything we've gone through so far leaving the fft length history
+ ret = 0;
+ break;
+ }
+
+ return ret;
+ }
+
+ } /* namespace digital */
+} /* namespace gr */