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Clock Manager: Detect Si5351 CLKIN present, measure frequency, and use if approximately 10MHz.
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parent
30f2bc4149
commit
88afee26d7
3 changed files with 35 additions and 4 deletions
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@ -269,11 +269,23 @@ void ClockManager::init() {
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clock_generator.enable_fanout();
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clock_generator.set_pll_input_sources(si5351_pll_input_sources);
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const bool use_clkin = false;
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const auto clkin_present = !clock_generator.clkin_loss_of_signal();
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auto clkin_valid = false;
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if( clkin_present ) {
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// Measure Si5351B CLKIN frequency against LPC43xx IRC oscillator
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set_gp_clkin_to_clkin_direct();
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start_frequency_monitor_measurement(cgu::CLK_SEL::GP_CLKIN);
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wait_For_frequency_monitor_measurement_done();
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const auto clkin_frequency = get_frequency_monitor_measurement_in_hertz();
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// CLKIN is required to be 10MHz. FREQ_MON measurement is accurate to 1.5%
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// due to LPC43xx IRC oscillator precision.
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clkin_valid = (clkin_frequency >= 9850000) && (clkin_frequency <= 10150000);
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}
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clock_generator.set_clock_control(
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use_clkin ?
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si5351_clock_control_clkin
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: si5351_clock_control_xtal
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clkin_valid ? si5351_clock_control_clkin : si5351_clock_control_xtal
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);
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clock_generator.write(si5351_pll_a_xtal_reg);
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@ -422,6 +434,14 @@ void ClockManager::disable_gp_clkin_source() {
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clock_generator.disable_output(clock_generator_output_mcu_clkin);
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}
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void ClockManager::set_gp_clkin_to_clkin_direct() {
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clock_generator.set_clock_control(
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clock_generator_output_mcu_clkin,
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{ ClockControl::CLK_IDRV_2mA | ClockControl::CLK_SRC_CLKIN | ClockControl::CLK_INV_Normal | ClockControl::MS_INT_Integer | ClockControl::CLK_PDN_Power_On }
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);
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enable_gp_clkin_source();
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}
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void ClockManager::start_frequency_monitor_measurement(const cgu::CLK_SEL clk_sel) {
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// Measure a clock input for 480 cycles of the LPC43xx IRC.
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LPC_CGU->FREQ_MON = LPC_CGU_FREQ_MON_Type {
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