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//
// Copyright 2016 Ettus Research LLC
// Copyright 2018 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: GPL-3.0-or-later
//
#include <uhd/exception.hpp>
#include <uhd/utils/math.hpp>
#include <uhdlib/usrp/cores/dsp_core_utils.hpp>
#include <cmath>
#include <limits>
static const int32_t MAX_FREQ_WORD = std::numeric_limits<int32_t>::max();
static const int32_t MIN_FREQ_WORD = std::numeric_limits<int32_t>::min();
void get_freq_and_freq_word(const double requested_freq,
const double tick_rate,
double& actual_freq,
int32_t& freq_word,
int word_width)
{
const double freq = uhd::math::wrap_frequency(requested_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, word_width);
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(std::lround((freq / tick_rate) * scale_factor));
}
actual_freq = (double(freq_word) / scale_factor) * tick_rate;
}
std::tuple<double, int> get_freq_and_freq_word(
const double requested_freq, const double tick_rate, int word_width)
{
double actual_freq;
int32_t freq_word;
get_freq_and_freq_word(requested_freq, tick_rate, actual_freq, freq_word, word_width);
return std::make_tuple(actual_freq, freq_word);
}
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