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#!/usr/bin/env python3
#
# OUTDATED
# This document is outdated because the VHF LO is not generated
# externally
from fractions import Fraction
from math import floor
xtal = 25
print()
print("# 116MHz and 4.915 MHz on PLLa")
PLLa = xtal * 32
print(f"PLLa = xtal * 32 = {PLLa} MHz")
# x/y = a + b/y
# a = floor(x/y)
# b = x - (a * y)
f1 = 116
a = floor(PLLa / f1)
b = PLLa - (a * f1)
div1 = Fraction(b, f1)
print(f"CLK1: f1 = PLLa / ({a} + {div1.numerator} / {div1.denominator}) = {f1}")
f2 = 4.91521
a = floor(PLLa / f2)
b = PLLa - (a * f2)
div1 = Fraction(round(b * 10000), round(f2 * 10000))
print(f"CLK2: f2 = PLLa / ({a} + {div1.numerator} / {div1.denominator}) = {f2}")
print()
print("# VFO between 23 and 25 MHz on PLLb")
def calculate(frequency):
divider = floor(900000000 / frequency) # Calculate the division ratio. 900,000,000 is the maximum internal
if divider % 2:
divider -= 1 # Ensure an even integer division ratio
pllFreq = round(divider * frequency) # Calculate the pllFrequency: the divider * desired output frequency
xtalFreq = xtal * 1000000
mult = floor(pllFreq / xtalFreq) # Determine the multiplier to get to the required pllFrequency
l = pllFreq % xtalFreq # It has three parts:
f = floor(l) # mult is an integer that must be in the range 15..90
denom = 1048575
f *= denom # num and denom are the fractional parts, the numerator and denominator
f /= xtalFreq # each is 20 bits (range 0..1048575)
num = floor(f) # the actual multiplier is mult + num / denom
return (divider, mult, num, denom)
vfo = 23000000
for i in range(10):
divider, mult, num, denom = calculate(vfo)
PLLb = xtal * 1000000 * (mult + num/denom)
freq = PLLb / divider
delta = vfo - freq
print(f"CLK0: VFO {vfo}, PLLb = xtal * ({mult} + {num} / {denom}) = {PLLb}, PLLb / {divider} = {freq}, delta = {delta:.03} Hz")
vfo += 100000
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