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Simplify PLL math when correcting for PPM.

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Jared Boone 2015-08-25 17:56:03 -07:00
parent 98773cb62a
commit 4974774f82
1 changed files with 3 additions and 2 deletions
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5
firmware/application/clock_manager.cpp
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@ -370,9 +370,10 @@ void ClockManager::set_sampling_frequency(const uint32_t frequency) {
void ClockManager::set_reference_ppb(const int32_t ppb) { void ClockManager::set_reference_ppb(const int32_t ppb) {
constexpr uint32_t pll_multiplier = si5351_pll_xtal_25m.a; 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_a = (ppb >= 0) ? pll_multiplier : (pll_multiplier - 1);
const uint32_t new_b = (ppb >= 0) ? (ppb * pll_multiplier / 1000) : (1000000 + (ppb * pll_multiplier / 1000)); const uint32_t new_b = (ppb >= 0) ? (ppb / 1000) : (denominator + (ppb / 1000));
const uint32_t new_c = (ppb == 0) ? 1 : 1000000; const uint32_t new_c = (ppb == 0) ? 1 : denominator;
const si5351::PLL pll { const si5351::PLL pll {
.f_in = si5351_inputs.f_xtal, .f_in = si5351_inputs.f_xtal,