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Clock Manager: Add API to measure LPC43xx clock inputs against IRC oscillator.

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This commit is contained in:
Jared Boone 2018-08-05 12:19:41 -07:00
parent 804ebd25aa
commit 30f2bc4149
2 changed files with 28 additions and 0 deletions
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24
firmware/application/clock_manager.cpp
View File

@ -422,6 +422,30 @@ void ClockManager::disable_gp_clkin_source() {
clock_generator.disable_output(clock_generator_output_mcu_clkin);
}
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::enable_xtal_oscillator() {
LPC_CGU->XTAL_OSC_CTRL.BYPASS = 0;
LPC_CGU->XTAL_OSC_CTRL.ENABLE = 1;

4
firmware/application/clock_manager.hpp
View File

@ -66,6 +66,8 @@ public:
void set_reference_ppb(const int32_t ppb);
uint32_t get_frequency_monitor_measurement_in_hertz();
private:
I2C& i2c0;
si5351::Si5351& clock_generator;
@ -75,6 +77,8 @@ private:
void enable_gp_clkin_source();
void disable_gp_clkin_source();
void start_frequency_monitor_measurement(const cgu::CLK_SEL clk_sel);
void wait_For_frequency_monitor_measurement_done();
void enable_xtal_oscillator();
void disable_xtal_oscillator();