From 88afee26d7bd708edc4e6a6be20475030d553255 Mon Sep 17 00:00:00 2001
From: Jared Boone <jboone@earfeast.com>
Date: Sun, 5 Aug 2018 12:21:25 -0700
Subject: [PATCH] Clock Manager: Detect Si5351 CLKIN present, measure
frequency, and use if approximately 10MHz.
---
firmware/application/clock_manager.cpp | 28 ++++++++++++++++++++++----
firmware/application/clock_manager.hpp | 2 ++
firmware/application/si5351.hpp | 9 +++++++++
3 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/firmware/application/clock_manager.cpp b/firmware/application/clock_manager.cpp
index 0cbf462f..fcddba0f 100644
--- a/firmware/application/clock_manager.cpp
+++ b/firmware/application/clock_manager.cpp
@@ -269,11 +269,23 @@ void ClockManager::init() {
clock_generator.enable_fanout();
clock_generator.set_pll_input_sources(si5351_pll_input_sources);
- const bool use_clkin = false;
+ const auto clkin_present = !clock_generator.clkin_loss_of_signal();
+ auto clkin_valid = false;
+
+ if( clkin_present ) {
+ // Measure Si5351B CLKIN frequency against LPC43xx IRC oscillator
+ set_gp_clkin_to_clkin_direct();
+ start_frequency_monitor_measurement(cgu::CLK_SEL::GP_CLKIN);
+ wait_For_frequency_monitor_measurement_done();
+ const auto clkin_frequency = get_frequency_monitor_measurement_in_hertz();
+
+ // CLKIN is required to be 10MHz. FREQ_MON measurement is accurate to 1.5%
+ // due to LPC43xx IRC oscillator precision.
+ clkin_valid = (clkin_frequency >= 9850000) && (clkin_frequency <= 10150000);
+ }
+
clock_generator.set_clock_control(
- use_clkin ?
- si5351_clock_control_clkin
- : si5351_clock_control_xtal
+ clkin_valid ? si5351_clock_control_clkin : si5351_clock_control_xtal
);
clock_generator.write(si5351_pll_a_xtal_reg);
@@ -422,6 +434,14 @@ void ClockManager::disable_gp_clkin_source() {
clock_generator.disable_output(clock_generator_output_mcu_clkin);
}
+void ClockManager::set_gp_clkin_to_clkin_direct() {
+ clock_generator.set_clock_control(
+ clock_generator_output_mcu_clkin,
+ { ClockControl::CLK_IDRV_2mA | ClockControl::CLK_SRC_CLKIN | ClockControl::CLK_INV_Normal | ClockControl::MS_INT_Integer | ClockControl::CLK_PDN_Power_On }
+ );
+ enable_gp_clkin_source();
+}
+
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 {
diff --git a/firmware/application/clock_manager.hpp b/firmware/application/clock_manager.hpp
index de36d374..5d4799ee 100644
--- a/firmware/application/clock_manager.hpp
+++ b/firmware/application/clock_manager.hpp
@@ -77,6 +77,8 @@ private:
void enable_gp_clkin_source();
void disable_gp_clkin_source();
+ void set_gp_clkin_to_clkin_direct();
+
void start_frequency_monitor_measurement(const cgu::CLK_SEL clk_sel);
void wait_For_frequency_monitor_measurement_done();
diff --git a/firmware/application/si5351.hpp b/firmware/application/si5351.hpp
index 58104f82..c7465d71 100644
--- a/firmware/application/si5351.hpp
+++ b/firmware/application/si5351.hpp
@@ -310,6 +310,10 @@ public:
while(device_status() & 0x80);
}
+ bool clkin_loss_of_signal() {
+ return (device_status() >> 4) & 1;
+ }
+
void enable_fanout() {
write_register(Register::FanoutEnable, 0b11010000);
}
@@ -373,6 +377,11 @@ public:
update_all_clock_control();
}
+ void set_clock_control(const size_t n, const ClockControl::Type clock_control) {
+ _clock_control[n] = clock_control;
+ write_register(Register::CLKControl_Base + n, _clock_control[n]);
+ }
+
void enable_clock(const size_t n) {
_clock_control[n] &= ~ClockControl::CLK_PDN_Mask;
write_register(Register::CLKControl_Base + n, _clock_control[n]);
--
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