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//
// Copyright 2013-2014 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 "adf435x_common.hpp"
#include <uhd/types/tune_request.hpp>
#include <uhd/utils/log.hpp>
using namespace uhd;
/***********************************************************************
* ADF 4350/4351 Tuning Utility
**********************************************************************/
adf435x_tuning_settings tune_adf435x_synth(
double target_freq,
double ref_freq,
const adf435x_tuning_constraints& constraints,
double& actual_freq)
{
//Default invalid value for actual_freq
actual_freq = 0;
double pfd_freq = 0;
boost::uint16_t R = 0, BS = 0, N = 0, FRAC = 0, MOD = 0;
boost::uint16_t RFdiv = static_cast<boost::uint16_t>(constraints.rf_divider_range.start());
bool D = false, T = false;
//Reference doubler for 50% duty cycle
//If ref_freq < 12.5MHz enable the reference doubler
D = (ref_freq <= constraints.ref_doubler_threshold);
static const double MIN_VCO_FREQ = 2.2e9;
static const double MAX_VCO_FREQ = 4.4e9;
//increase RF divider until acceptable VCO frequency
double vco_freq = target_freq;
while (vco_freq < MIN_VCO_FREQ && RFdiv < static_cast<boost::uint16_t>(constraints.rf_divider_range.stop())) {
vco_freq *= 2;
RFdiv *= 2;
}
/*
* The goal here is to loop though possible R dividers,
* band select clock dividers, N (int) dividers, and FRAC
* (frac) dividers.
*
* Calculate the N and F dividers for each set of values.
* The loop exits when it meets all of the constraints.
* The resulting loop values are loaded into the registers.
*
* from pg.21
*
* f_pfd = f_ref*(1+D)/(R*(1+T))
* f_vco = (N + (FRAC/MOD))*f_pfd
* N = f_vco/f_pfd - FRAC/MOD = f_vco*((R*(T+1))/(f_ref*(1+D))) - FRAC/MOD
* f_rf = f_vco/RFdiv)
* f_actual = f_rf/2
*/
for(R = 1; R <= 1023; R+=1){
//PFD input frequency = f_ref/R ... ignoring Reference doubler/divide-by-2 (D & T)
pfd_freq = ref_freq*(D?2:1)/(R*(T?2:1));
//keep the PFD frequency at or below 25MHz (Loop Filter Bandwidth)
if (pfd_freq > constraints.pfd_freq_max) continue;
//ignore fractional part of tuning
//N is computed from target_freq and not vco_freq because the feedback
//mode is set to FEEDBACK_SELECT_DIVIDED
N = boost::uint16_t(std::floor(target_freq/pfd_freq));
//keep N > minimum int divider requirement
if (N < static_cast<boost::uint16_t>(constraints.int_range.start())) continue;
for(BS=1; BS <= 255; BS+=1){
//keep the band select frequency at or below band_sel_freq_max
//constraint on band select clock
if (pfd_freq/BS > constraints.band_sel_freq_max) continue;
goto done_loop;
}
} done_loop:
//Fractional-N calculation
MOD = 4095; //max fractional accuracy
//N is computed from target_freq and not vco_freq because the feedback
//mode is set to FEEDBACK_SELECT_DIVIDED
FRAC = static_cast<boost::uint16_t>((target_freq/pfd_freq - N)*MOD);
if (constraints.force_frac0) {
if (FRAC > (MOD / 2)) { //Round integer such that actual freq is closest to target
N++;
}
FRAC = 0;
}
//Reference divide-by-2 for 50% duty cycle
// if R even, move one divide by 2 to to regs.reference_divide_by_2
if(R % 2 == 0) {
T = true;
R /= 2;
}
//Typical phase resync time documented in data sheet pg.24
static const double PHASE_RESYNC_TIME = 400e-6;
//actual frequency calculation
actual_freq = double((N + (double(FRAC)/double(MOD)))*ref_freq*(D?2:1)/(R*(T?2:1)));
//load the settings
adf435x_tuning_settings settings;
settings.frac_12_bit = FRAC;
settings.int_16_bit = N;
settings.mod_12_bit = MOD;
settings.clock_divider_12_bit = std::max<boost::uint16_t>(1, std::ceil(PHASE_RESYNC_TIME*pfd_freq/MOD));
settings.r_counter_10_bit = R;
settings.r_divide_by_2_en = T;
settings.r_doubler_en = D;
settings.band_select_clock_div = BS;
settings.rf_divider = RFdiv;
settings.feedback_after_divider = true;
std::string tuning_str = (constraints.force_frac0) ? "Integer-N" : "Fractional";
UHD_LOGV(often)
<< boost::format("ADF 435X Frequencies (MHz): REQUESTED=%0.9f, ACTUAL=%0.9f"
) % (target_freq/1e6) % (actual_freq/1e6) << std::endl
<< boost::format("ADF 435X Intermediates (MHz): VCO=%0.2f, PFD=%0.2f, BAND=%0.2f, REF=%0.2f"
) % (vco_freq/1e6) % (pfd_freq/1e6) % (pfd_freq/BS/1e6) % (ref_freq/1e6) << std::endl
<< boost::format("ADF 435X Tuning: %s") % tuning_str.c_str() << std::endl
<< boost::format("ADF 435X Settings: R=%d, BS=%d, N=%d, FRAC=%d, MOD=%d, T=%d, D=%d, RFdiv=%d"
) % R % BS % N % FRAC % MOD % T % D % RFdiv << std::endl;
UHD_ASSERT_THROW((settings.frac_12_bit & ((boost::uint16_t)~0xFFF)) == 0);
UHD_ASSERT_THROW((settings.mod_12_bit & ((boost::uint16_t)~0xFFF)) == 0);
UHD_ASSERT_THROW((settings.clock_divider_12_bit & ((boost::uint16_t)~0xFFF)) == 0);
UHD_ASSERT_THROW((settings.r_counter_10_bit & ((boost::uint16_t)~0x3FF)) == 0);
UHD_ASSERT_THROW(vco_freq >= MIN_VCO_FREQ and vco_freq <= MAX_VCO_FREQ);
UHD_ASSERT_THROW(settings.rf_divider >= static_cast<boost::uint16_t>(constraints.rf_divider_range.start()));
UHD_ASSERT_THROW(settings.rf_divider <= static_cast<boost::uint16_t>(constraints.rf_divider_range.stop()));
UHD_ASSERT_THROW(settings.int_16_bit >= static_cast<boost::uint16_t>(constraints.int_range.start()));
UHD_ASSERT_THROW(settings.int_16_bit <= static_cast<boost::uint16_t>(constraints.int_range.stop()));
return settings;
}
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