portapack-mayhem/firmware/application/clock_manager.cpp

/*
 * Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
 *
 * This file is part of PortaPack.
 *
 * 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 2, 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; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#include "clock_manager.hpp"

#include "portapack_persistent_memory.hpp"
#include "portapack_io.hpp"

#include "hackrf_hal.hpp"
using namespace hackrf::one;

#include "lpc43xx_cpp.hpp"
using namespace lpc43xx;

constexpr uint32_t si5351_vco_f = 800000000;

constexpr si5351::Inputs si5351_inputs{
    .f_xtal = si5351_xtal_f,
    .f_clkin = si5351_clkin_f,
    .clkin_div = 1,
};

static_assert(si5351_inputs.f_xtal == si5351_xtal_f, "XTAL output frequency wrong");
static_assert(si5351_inputs.f_clkin_out() == si5351_clkin_f, "CLKIN output frequency wrong");

constexpr si5351::PLLInputSource::Type si5351c_pll_input_sources{
    si5351::PLLInputSource::PLLA_Source_XTAL | si5351::PLLInputSource::PLLB_Source_CLKIN | si5351::PLLInputSource::CLKIN_Div1};

constexpr si5351::PLLInputSource::Type si5351a_pll_input_sources{
    si5351::PLLInputSource::PLLA_Source_XTAL | si5351::PLLInputSource::PLLB_Source_XTAL | si5351::PLLInputSource::CLKIN_Div1};

constexpr si5351::PLL si5351_pll_xtal_25m{
    .f_in = si5351_inputs.f_xtal,
    .a = 32,
    .b = 0,
    .c = 1,
};
constexpr auto si5351_pll_a_xtal_reg = si5351_pll_xtal_25m.reg(0);

constexpr si5351::PLL si5351_pll_clkin_10m{
    .f_in = si5351_inputs.f_clkin_out(),
    .a = 80,
    .b = 0,
    .c = 1,
};
constexpr auto si5351c_pll_b_clkin_reg = si5351_pll_clkin_10m.reg(1);
constexpr auto si5351a_pll_a_clkin_reg = si5351_pll_clkin_10m.reg(0);

static_assert(si5351_pll_xtal_25m.f_vco() == si5351_vco_f, "PLL XTAL frequency wrong");
static_assert(si5351_pll_xtal_25m.p1() == 3584, "PLL XTAL P1 wrong");
static_assert(si5351_pll_xtal_25m.p2() == 0, "PLL XTAL P2 wrong");
static_assert(si5351_pll_xtal_25m.p3() == 1, "PLL XTAL P3 wrong");

static_assert(si5351_pll_clkin_10m.f_vco() == si5351_vco_f, "PLL CLKIN frequency wrong");
static_assert(si5351_pll_clkin_10m.p1() == 9728, "PLL CLKIN P1 wrong");
static_assert(si5351_pll_clkin_10m.p2() == 0, "PLL CLKIN P2 wrong");
static_assert(si5351_pll_clkin_10m.p3() == 1, "PLL CLKIN P3 wrong");
/*
constexpr si5351::MultisynthFractional si5351_ms_18m432 {
        .f_src = si5351_vco_f,
        .a = 43,
        .b = 29,
        .c = 72,
        .r_div = 1,
};
*/
/*
constexpr si5351::MultisynthFractional si5351_ms_0_20m {
        .f_src = si5351_vco_f,
        .a = 20,
        .b = 0,
        .c = 1,
        .r_div = 1,
};
constexpr auto si5351_ms_0_20m_reg = si5351_ms_0_20m.reg(0);
*/
constexpr si5351::MultisynthFractional si5351_ms_0_8m{
    .f_src = si5351_vco_f,
    .a = 50,
    .b = 0,
    .c = 1,
    .r_div = 1,
};
constexpr auto si5351c_ms_0_8m_reg = si5351_ms_0_8m.reg(clock_generator_output_og_codec);

constexpr si5351::MultisynthFractional si5351_ms_group{
    .f_src = si5351_vco_f,
    .a = 80, /* Don't care */
    .b = 0,
    .c = 1,
    .r_div = 0,
};
constexpr auto si5351c_ms_1_group_reg = si5351_ms_group.reg(clock_generator_output_og_cpld);
constexpr auto si5351c_ms_2_group_reg = si5351_ms_group.reg(clock_generator_output_og_sgpio);

constexpr si5351::MultisynthFractional si5351_ms_16m{
    .f_src = si5351_vco_f,
    .a = 50,
    .b = 0,
    .c = 1,
    .r_div = 0,
};
constexpr auto si5351a_ms_1_sgpio_16m_reg = si5351_ms_16m.reg(clock_generator_output_r9_sgpio);

constexpr si5351::MultisynthFractional si5351_ms_10m{
    .f_src = si5351_vco_f,
    .a = 80,
    .b = 0,
    .c = 1,
    .r_div = 0,
};
constexpr auto si5351c_ms_3_10m_reg = si5351_ms_10m.reg(3);
constexpr auto si5351a_ms_2_mcu_10m_reg = si5351_ms_10m.reg(clock_generator_output_r9_mcu_clkin);

constexpr si5351::MultisynthFractional si5351_ms_40m{
    .f_src = si5351_vco_f,
    .a = 20,
    .b = 0,
    .c = 1,
    .r_div = 0,
};

constexpr auto si5351_ms_rffc5072 = si5351_ms_40m;
constexpr auto si5351_ms_max283x = si5351_ms_40m;

constexpr auto si5351c_ms_4_reg = si5351_ms_rffc5072.reg(clock_generator_output_og_first_if);
constexpr auto si5351c_ms_5_reg = si5351_ms_max283x.reg(clock_generator_output_og_second_if);
constexpr auto si5351a_ms_0_if_40m_reg = si5351_ms_40m.reg(clock_generator_output_r9_if);

static_assert(si5351_ms_10m.f_out() == 10000000, "MS 10MHz f_out wrong");
static_assert(si5351_ms_10m.p1() == 9728, "MS 10MHz p1 wrong");
static_assert(si5351_ms_10m.p2() == 0, "MS 10MHz p2 wrong");
static_assert(si5351_ms_10m.p3() == 1, "MS 10MHz p3 wrong");

static_assert(si5351_ms_rffc5072.f_out() == rffc5072_reference_f, "RFFC5072 reference f_out wrong");

static_assert(si5351_ms_max283x.f_out() == max283x_reference_f, "MAX283x reference f_out wrong");

constexpr si5351::MultisynthInteger si5351_ms_int_off{
    .f_src = si5351_vco_f,
    .a = 255,
    .r_div = 0,
};

constexpr si5351::MultisynthInteger si5351_ms_int_40m{
    .f_src = si5351_vco_f,
    .a = 20,
    .r_div = 0,
};

constexpr si5351::MultisynthInteger si5351_ms_int_10m{
    .f_src = si5351_vco_f,
    .a = 80,
    .r_div = 0,
};

constexpr auto si5351c_ms_int_mcu_clkin = si5351_ms_int_40m;
constexpr auto si5351a_ms_int_mcu_clkin = si5351_ms_int_10m;

constexpr auto si5351c_ms6_7_off_mcu_clkin_reg = si5351::ms6_7_reg(si5351_ms_int_off, si5351c_ms_int_mcu_clkin);
constexpr auto si5351a_ms6_7_off_reg = si5351::ms6_7_reg(si5351_ms_int_off, si5351_ms_int_off);

static_assert(si5351_ms_int_off.f_out() == 3137254, "MS int off f_out wrong");
static_assert(si5351_ms_int_off.p1() == 255, "MS int off P1 wrong");

static_assert(si5351c_ms_int_mcu_clkin.f_out() == mcu_clkin_og_f, "MS int MCU CLKIN OG f_out wrong");
static_assert(si5351a_ms_int_mcu_clkin.f_out() == mcu_clkin_r9_f, "MS int MCU CLKIN r9 f_out wrong");

using namespace si5351;

static constexpr ClockControl::MultiSynthSource get_si5351c_reference_clock_generator_pll(const ClockManager::ReferenceSource reference_source) {
    return (reference_source == ClockManager::ReferenceSource::Xtal)
               ? ClockControl::MultiSynthSource::PLLA
               : ClockControl::MultiSynthSource::PLLB;
}

constexpr ClockControls si5351c_clock_control_common{{
    {ClockControl::ClockCurrentDrive::_8mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Fractional, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Group, ClockControl::ClockInvert::Invert, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Group, ClockControl::ClockInvert::Normal, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_8mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_6mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Invert, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_4mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Fractional, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, get_si5351c_reference_clock_generator_pll(ClockManager::ReferenceSource::Xtal), ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
}};

constexpr ClockControls si5351a_clock_control_common{{
    {ClockControl::ClockCurrentDrive::_6mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_4mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Fractional, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_8mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
    {ClockControl::ClockCurrentDrive::_2mA, ClockControl::ClockSource::MS_Self, ClockControl::ClockInvert::Normal, ClockControl::MultiSynthSource::PLLA, ClockControl::MultiSynthMode::Integer, ClockControl::ClockPowerDown::Power_Off},
}};
ClockManager::Reference ClockManager::get_reference() const {
    return reference;
}

std::string ClockManager::get_source() {
    std::string source_name("---");
    switch (reference.source) {
        case ClockManager::ReferenceSource::Xtal:
            source_name = "HackRF";
            break;
        case ClockManager::ReferenceSource::PortaPack:
            source_name = "PortaPack";
            break;
        case ClockManager::ReferenceSource::External:
            source_name = "External";
            break;
    }
    return source_name;
}

std::string ClockManager::get_freq() {
    return to_string_dec_uint(reference.frequency / 1000000, 2) + "." +
           to_string_dec_uint((reference.frequency % 1000000) / 100, 4, '0') + " MHz";
}

static void portapack_tcxo_enable() {
    portapack::io.reference_oscillator(true);

    /* Delay >10ms at 96MHz clock speed for reference oscillator to start. */
    /* Delay an additional 1ms (arbitrary) for the clock generator to detect a signal. */
    volatile uint32_t delay = 240000 + 24000;
    while (delay--)
        ;
}

static void portapack_tcxo_disable() {
    portapack::io.reference_oscillator(false);
}

#include "hackrf_gpio.hpp"
using namespace hackrf::one;

void ClockManager::init_clock_generator() {
    clock_generator.reset();
    clock_generator.set_crystal_internal_load_capacitance(CrystalInternalLoadCapacitance::XTAL_CL_8pF);
    clock_generator.enable_fanout();
    clock_generator.set_pll_input_sources(hackrf_r9
                                              ? si5351a_pll_input_sources
                                              : si5351c_pll_input_sources);

    auto si5351_clock_control_common = hackrf_r9
                                           ? si5351a_clock_control_common
                                           : si5351c_clock_control_common;

    auto clock_generator_output_mcu_clkin = hackrf_r9
                                                ? clock_generator_output_r9_mcu_clkin
                                                : clock_generator_output_og_mcu_clkin;

    clock_generator.set_clock_control(
        clock_generator_output_mcu_clkin,
        si5351_clock_control_common[clock_generator_output_mcu_clkin]
            .clk_src(hackrf_r9
                         ? ClockControl::ClockSource::Xtal
                         : ClockControl::ClockSource::CLKIN)
            .clk_pdn(ClockControl::ClockPowerDown::Power_On));
    clock_generator.enable_output(clock_generator_output_mcu_clkin);

    reference = choose_reference();

    clock_generator.disable_output(clock_generator_output_mcu_clkin);

    const auto ref_pll = hackrf_r9
                             ? ClockControl::MultiSynthSource::PLLA
                             : get_si5351c_reference_clock_generator_pll(reference.source);

    const ClockControls si5351_clock_control = ClockControls{{
        si5351_clock_control_common[0].ms_src(ref_pll),
        si5351_clock_control_common[1].ms_src(ref_pll),
        si5351_clock_control_common[2].ms_src(ref_pll),
        si5351_clock_control_common[3].ms_src(ref_pll),
        si5351_clock_control_common[4].ms_src(ref_pll),
        si5351_clock_control_common[5].ms_src(ref_pll),
        si5351_clock_control_common[6].ms_src(ref_pll),
        si5351_clock_control_common[7].ms_src(ref_pll),
    }};
    clock_generator.set_clock_control(si5351_clock_control);

    if (hackrf_r9) {
        const PLLReg pll_reg = (reference.source == ReferenceSource::Xtal)
                                   ? si5351_pll_a_xtal_reg
                                   : si5351a_pll_a_clkin_reg;
        clock_generator.write(pll_reg);
        clock_generator.write(si5351a_ms_0_if_40m_reg);
        clock_generator.write(si5351a_ms_1_sgpio_16m_reg);
        clock_generator.write(si5351a_ms_2_mcu_10m_reg);
        clock_generator.write(si5351a_ms6_7_off_reg);
    } else {
        clock_generator.write(si5351_pll_a_xtal_reg);
        clock_generator.write(si5351c_pll_b_clkin_reg);
        clock_generator.write(si5351c_ms_0_8m_reg);
        clock_generator.write(si5351c_ms_1_group_reg);
        clock_generator.write(si5351c_ms_2_group_reg);
        clock_generator.write(si5351c_ms_3_10m_reg);
        clock_generator.write(si5351c_ms_4_reg);
        clock_generator.write(si5351c_ms_5_reg);
        clock_generator.write(si5351c_ms6_7_off_mcu_clkin_reg);
    }

    clock_generator.reset_plls();

    // Wait for PLL(s) to lock.
    uint8_t device_status_mask = hackrf_r9
                                     ? 0x20
                                 : (ref_pll == ClockControl::MultiSynthSource::PLLB)
                                     ? 0x40
                                     : 0x20;
    while ((clock_generator.device_status() & device_status_mask) != 0)
        ;

    clock_generator.set_clock_control(
        clock_generator_output_mcu_clkin,
        si5351_clock_control_common[clock_generator_output_mcu_clkin].ms_src(ref_pll).clk_pdn(ClockControl::ClockPowerDown::Power_On));
    clock_generator.enable_output(clock_generator_output_mcu_clkin);
}

uint32_t ClockManager::measure_gp_clkin_frequency() {
    // Measure Si5351B CLKIN frequency against LPC43xx IRC oscillator
    start_frequency_monitor_measurement(cgu::CLK_SEL::GP_CLKIN);
    wait_For_frequency_monitor_measurement_done();
    return get_frequency_monitor_measurement_in_hertz();
}

bool ClockManager::loss_of_signal() {
    if (hackrf_r9) {
        const auto frequency = measure_gp_clkin_frequency();
        return (frequency < 9850000) || (frequency > 10150000);
    } else {
        return clock_generator.clkin_loss_of_signal();
    }
}

ClockManager::ReferenceSource ClockManager::detect_reference_source() {
    if (portapack::persistent_memory::config_disable_external_tcxo())
        return ReferenceSource::Xtal;

    if (loss_of_signal()) {
        // No external reference. Turn on PortaPack reference (if present).
        portapack_tcxo_enable();

        if (loss_of_signal()) {
            // No PortaPack reference was detected. Choose the HackRF crystal as the reference.
            return ReferenceSource::Xtal;
        } else {
            return ReferenceSource::PortaPack;
        }
    } else {
        return ReferenceSource::External;
    }
}

ClockManager::Reference ClockManager::choose_reference() {
    if (hackrf_r9) {
        gpio_r9_clkin_en.write(1);
        volatile uint32_t delay = 240000 + 24000;
        while (delay--)
            ;
    }
    const auto detected_reference = detect_reference_source();

    if ((detected_reference == ReferenceSource::External) ||
        (detected_reference == ReferenceSource::PortaPack)) {
        const auto frequency = measure_gp_clkin_frequency();
        if ((frequency >= 9850000) && (frequency <= 10150000)) {
            return {detected_reference, 10000000};
        }
    }

    if (hackrf_r9) {
        gpio_r9_clkin_en.write(0);
    }

    portapack_tcxo_disable();
    return {ReferenceSource::Xtal, 25000000};
}

void ClockManager::shutdown() {
    clock_generator.reset();
}

void ClockManager::enable_codec_clocks() {
    if (hackrf_r9) {
        clock_generator.enable_clock(clock_generator_output_r9_sgpio);
    } else {
        clock_generator.enable_clock(clock_generator_output_og_codec);
        clock_generator.enable_clock(clock_generator_output_og_cpld);
        clock_generator.enable_clock(clock_generator_output_og_sgpio);
    }
    /* Turn on all outputs at the same time. This probably doesn't ensure
     * their phase relationships. For example, clocks that output frequencies
     * in a 2:1 relationship may start with the slower clock high or low?
     */
    if (hackrf_r9) {
        clock_generator.enable_output_mask(1U << clock_generator_output_r9_sgpio);
    } else {
        clock_generator.enable_output_mask(
            (1U << clock_generator_output_og_codec) | (1U << clock_generator_output_og_cpld) | (1U << clock_generator_output_og_sgpio));
    }
}

void ClockManager::disable_codec_clocks() {
    /* Turn off outputs before disabling clocks. It seems the clock needs to
     * be enabled for the output to come to rest at the state specified by
     * CLKx_DISABLE_STATE.
     */
    if (hackrf_r9) {
        clock_generator.disable_output_mask(1U << clock_generator_output_r9_sgpio);
        clock_generator.disable_clock(clock_generator_output_r9_sgpio);
    } else {
        clock_generator.disable_output_mask(
            (1U << clock_generator_output_og_codec) | (1U << clock_generator_output_og_cpld) | (1U << clock_generator_output_og_sgpio));
        clock_generator.disable_clock(clock_generator_output_og_codec);
        clock_generator.disable_clock(clock_generator_output_og_cpld);
        clock_generator.disable_clock(clock_generator_output_og_sgpio);
    }
}

void ClockManager::enable_if_clocks() {
    if (hackrf_r9) {
        clock_generator.enable_clock(clock_generator_output_r9_if);
        clock_generator.enable_output_mask(1U << clock_generator_output_r9_if);
    } else {
        clock_generator.enable_clock(clock_generator_output_og_first_if);
        clock_generator.enable_output_mask(1U << clock_generator_output_og_first_if);
        clock_generator.enable_clock(clock_generator_output_og_second_if);
        clock_generator.enable_output_mask(1U << clock_generator_output_og_second_if);
    }
}

void ClockManager::disable_if_clocks() {
    if (hackrf_r9) {
        clock_generator.disable_output_mask(1U << clock_generator_output_r9_if);
        clock_generator.disable_clock(clock_generator_output_r9_if);
    } else {
        clock_generator.disable_output_mask(1U << clock_generator_output_og_first_if);
        clock_generator.disable_clock(clock_generator_output_og_first_if);
        clock_generator.disable_output_mask(1U << clock_generator_output_og_second_if);
        clock_generator.disable_clock(clock_generator_output_og_second_if);
    }
}

void ClockManager::set_sampling_frequency(const uint32_t frequency) {
    /* Codec clock is at sampling frequency, CPLD and SGPIO clocks are at
     * twice the frequency, and derived from the MS0 synth. So it's only
     * necessary to change the MS0 synth frequency, and ensure the output
     * is divided by two.
     */
    if (hackrf_r9) {
        clock_generator.set_ms_frequency(clock_generator_output_r9_sgpio, frequency * 2, si5351_vco_f, 0);
    } else {
        clock_generator.set_ms_frequency(clock_generator_output_og_codec, frequency * 2, si5351_vco_f, 1);
    }
}

void ClockManager::set_reference_ppb(const int32_t ppb) {
    /* NOTE: This adjustment only affects PLLA when it is derived from the 25MHz crystal.
     * It is assumed an external clock coming in to CLKIN/PLLB is sufficiently accurate as to not need adjustment.
     * TODO: Revisit the above policy. It may be good to allow adjustment of the external reference too.
     */
    if (hackrf_r9 && reference.source != ReferenceSource::Xtal) {
        return;
    }
    constexpr uint32_t pll_multiplier = si5351_pll_xtal_25m.a;
    constexpr uint32_t denominator = 1000000 / pll_multiplier;
    const uint32_t new_a = (ppb >= 0) ? pll_multiplier : (pll_multiplier - 1);
    const uint32_t new_b = (ppb >= 0) ? (ppb / 1000) : (denominator + (ppb / 1000));
    const uint32_t new_c = (ppb == 0) ? 1 : denominator;

    const si5351::PLL pll{
        .f_in = si5351_inputs.f_xtal,
        .a = new_a,
        .b = new_b,
        .c = new_c,
    };
    const auto pll_a_reg = pll.reg(0);
    clock_generator.write(pll_a_reg);
}

void ClockManager::start_frequency_monitor_measurement(const cgu::CLK_SEL clk_sel) {
    // Measure a clock input for 480 cycles of the LPC43xx IRC.
    LPC_CGU->FREQ_MON = LPC_CGU_FREQ_MON_Type{
        .RCNT = 480,
        .FCNT = 0,
        .MEAS = 0,
        .CLK_SEL = toUType(clk_sel),
        .RESERVED0 = 0};
    LPC_CGU->FREQ_MON.MEAS = 1;
}

void ClockManager::wait_For_frequency_monitor_measurement_done() {
    // FREQ_MON mechanism fails to finish if there's no clock present on selected input?!
    while (LPC_CGU->FREQ_MON.MEAS == 1)
        ;
}

uint32_t ClockManager::get_frequency_monitor_measurement_in_hertz() {
    // Measurement is only as accurate as the LPC43xx IRC oscillator,
    // which is +/- 1.5%. Measurement is for 480 IRC clcocks. Scale
    // the cycle count to get a value in Hertz.
    return LPC_CGU->FREQ_MON.FCNT * 25000;
}

void ClockManager::start_audio_pll() {
    cgu::pll0audio::ctrl({
        .pd = 1,
        .bypass = 0,
        .directi = 0,
        .directo = 0,
        .clken = 0,
        .frm = 0,
        .autoblock = 1,
        .pllfract_req = 0,
        .sel_ext = 1,
        .mod_pd = 1,
        .clk_sel = cgu::CLK_SEL::GP_CLKIN,
    });

    /* For 40MHz clock source, 48kHz audio rate, 256Fs MCLK:
     * 		Fout=12.288MHz, Fcco=491.52MHz
     *	OG:	PSEL=20, NSEL=125, MSEL=768
     *		PDEC=31, NDEC=45, MDEC=30542
     *	r9:	PSEL=20, NSEL=125, MSEL=3072
     *		PDEC=31, NDEC=45, MDEC=8308
     */
    cgu::pll0audio::mdiv({
        .mdec = hackrf_r9 ? 8308UL : 30542UL,
    });
    cgu::pll0audio::np_div({
        .pdec = 31,
        .ndec = 45,
    });

    cgu::pll0audio::frac({
        .pllfract_ctrl = 0,
    });

    cgu::pll0audio::power_up();
    while (!cgu::pll0audio::is_locked())
        ;
    cgu::pll0audio::clock_enable();

    set_base_audio_clock_divider(1);

    LPC_CGU->BASE_AUDIO_CLK.AUTOBLOCK = 1;
    LPC_CGU->BASE_AUDIO_CLK.CLK_SEL = toUType(cgu::CLK_SEL::IDIVD);
}

void ClockManager::set_base_audio_clock_divider(const size_t divisor) {
    LPC_CGU->IDIVD_CTRL.word =
        (0 << 0) | ((divisor - 1) << 2) | (1 << 11) | (toUType(cgu::CLK_SEL::PLL0AUDIO) << 24);
}

void ClockManager::stop_audio_pll() {
    cgu::pll0audio::clock_disable();
    cgu::pll0audio::power_down();
    while (cgu::pll0audio::is_locked())
        ;
}

void ClockManager::enable_clock_output(bool enable) {
    if (hackrf_r9) {
        gpio_r9_clkout_en.output();
        gpio_r9_clkout_en.write(enable);

        // NOTE: RETURNING HERE IF HACKRF_R9 TO PREVENT CLK2 FROM BEING DISABLED OR FREQ MODIFIED SINCE CLK2 ON R9 IS
        // USED FOR BOTH CLKOUT AND FOR THE MCU_CLOCK (== GP_CLKIN) WHICH OTHER LP43XX CLOCKS CURRENTLY RELY ON.
        // FUTURE TBD: REMOVE OTHER LP43XX CLOCK DEPENDENCIES ON GP_CLKIN, THEN DELETE THE return LINE BELOW TO ALLOW
        // CLKOUT FREQ CHANGES ON R9 BOARDS.
        return;
    }

    auto clkout_select = hackrf_r9 ? clock_generator_output_r9_clkout : clock_generator_output_og_clkout;

    if (enable) {
        clock_generator.enable_output(clkout_select);
        if (portapack::persistent_memory::clkout_freq() < 1000) {
            clock_generator.set_ms_frequency(clkout_select, portapack::persistent_memory::clkout_freq() * 128000, si5351_vco_f, 7);
        } else {
            clock_generator.set_ms_frequency(clkout_select, portapack::persistent_memory::clkout_freq() * 1000, si5351_vco_f, 0);
        }

        auto si5351_clock_control_common = hackrf_r9 ? si5351a_clock_control_common : si5351c_clock_control_common;
        const auto ref_pll = hackrf_r9 ? ClockControl::MultiSynthSource::PLLA : get_si5351c_reference_clock_generator_pll(reference.source);
        clock_generator.set_clock_control(clkout_select, si5351_clock_control_common[clkout_select].ms_src(ref_pll).clk_pdn(ClockControl::ClockPowerDown::Power_On));
    } else {
        clock_generator.disable_output(clkout_select);
        clock_generator.set_clock_control(clkout_select, ClockControl::power_off());
    }
}