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34 lines
768 B
34 lines
768 B
3 years ago
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// Uses the built in Real Time Clock (RTC) as timebase.
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// The sketch calculates the relative drift of the main 24MHz crystal relative to the 32.768kHz RTC crystal.
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// Requires a T4.x board
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#include "Arduino.h"
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#include "TeensyTimerTool.h"
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using namespace TeensyTimerTool;
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PeriodicTimer t1(TCK_RTC);
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constexpr uint32_t period = 500'000; //µs
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void callback()
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{
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static uint32_t start = micros();
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static uint32_t idx = 0;
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uint32_t now = micros() - start;
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uint32_t expected = idx++ * period;
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int32_t delta = now - expected;
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float drift = 1E6 * delta / expected; // ppm
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Serial.printf("t: %d µs, rel. drift: %.2f ppm\n", now, drift);
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}
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void setup()
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{
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t1.begin(callback, period);
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}
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void loop()
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{
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}
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