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//
// Copyright 2016 Ettus Research LLC
//
// This program 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 of the License, or
// (at your option) any later version.
//
// This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
//
#include "dsp_core_utils.hpp"
#include <uhd/utils/math.hpp>
#include <uhd/exception.hpp>
#include <boost/math/special_functions/round.hpp>
#include <boost/math/special_functions/sign.hpp>
static const int32_t MAX_FREQ_WORD = boost::numeric::bounds<int32_t>::highest();
static const int32_t MIN_FREQ_WORD = boost::numeric::bounds<int32_t>::lowest();
void get_freq_and_freq_word(
const double requested_freq,
const double tick_rate,
double &actual_freq,
int32_t &freq_word
) {
//correct for outside of rate (wrap around)
double freq = std::fmod(requested_freq, tick_rate);
if (std::abs(freq) > tick_rate/2.0)
freq -= boost::math::sign(freq) * tick_rate;
//confirm that the target frequency is within range of the CORDIC
UHD_ASSERT_THROW(std::abs(freq) <= tick_rate/2.0);
/* Now calculate the frequency word. It is possible for this calculation
* to cause an overflow. As the requested DSP frequency approaches the
* master clock rate, that ratio multiplied by the scaling factor (2^32)
* will generally overflow within the last few kHz of tunable range.
* Thus, we check to see if the operation will overflow before doing it,
* and if it will, we set it to the integer min or max of this system.
*/
freq_word = 0;
static const double scale_factor = std::pow(2.0, 32);
if ((freq / tick_rate) >= (MAX_FREQ_WORD / scale_factor)) {
/* Operation would have caused a positive overflow of int32. */
freq_word = MAX_FREQ_WORD;
} else if ((freq / tick_rate) <= (MIN_FREQ_WORD / scale_factor)) {
/* Operation would have caused a negative overflow of int32. */
freq_word = MIN_FREQ_WORD;
} else {
/* The operation is safe. Perform normally. */
freq_word = int32_t(boost::math::round((freq / tick_rate) * scale_factor));
}
actual_freq = (double(freq_word) / scale_factor) * tick_rate;
}
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