1#!/usr/bin/env python3
2
3import argparse
4import sys
5
6# Fixed hardware parameters
7fbdiv_range = range(16, 320 + 1)
8postdiv_range = range(1, 7 + 1)
9ref_min = 5
10refdiv_min = 1
11refdiv_max = 63
12
13def validRefdiv(string):
14    if ((int(string) < refdiv_min) or (int(string) > refdiv_max)):
15        raise ValueError("REFDIV must be in the range {} to {}".format(refdiv_min, refdiv_max))
16    return int(string)
17
18parser = argparse.ArgumentParser(description="PLL parameter calculator")
19parser.add_argument("--input", "-i", default=12, help="Input (reference) frequency. Default 12 MHz", type=float)
20parser.add_argument("--ref-min", default=5, help="Override minimum reference frequency. Default 5 MHz", type=float)
21parser.add_argument("--vco-max", default=1600, help="Override maximum VCO frequency. Default 1600 MHz", type=float)
22parser.add_argument("--vco-min", default=750, help="Override minimum VCO frequency. Default 750 MHz", type=float)
23parser.add_argument("--cmake", action="store_true", help="Print out a CMake snippet to apply the selected PLL parameters to your program")
24parser.add_argument("--cmake-only", action="store_true", help="Same as --cmake, but do not print anything other than the CMake output")
25parser.add_argument("--cmake-executable-name", default="<program>", help="Set the executable name to use in the generated CMake output")
26parser.add_argument("--lock-refdiv", help="Lock REFDIV to specified number in the range {} to {}".format(refdiv_min, refdiv_max), type=validRefdiv)
27parser.add_argument("--low-vco", "-l", action="store_true", help="Use a lower VCO frequency when possible. This reduces power consumption, at the cost of increased jitter")
28parser.add_argument("output", help="Output frequency in MHz.", type=float)
29args = parser.parse_args()
30
31refdiv_range = range(refdiv_min, max(refdiv_min, min(refdiv_max, int(args.input / args.ref_min))) + 1)
32if args.lock_refdiv:
33	print("Locking REFDIV to", args.lock_refdiv)
34	refdiv_range = [args.lock_refdiv]
35
36best = (0, 0, 0, 0, 0, 0)
37best_margin = args.output
38
39for refdiv in refdiv_range:
40	for fbdiv in fbdiv_range:
41		vco = args.input / refdiv * fbdiv
42		if vco < args.vco_min or vco > args.vco_max:
43			continue
44		# pd1 is inner loop so that we prefer higher ratios of pd1:pd2
45		for pd2 in postdiv_range:
46			for pd1 in postdiv_range:
47				out = vco / pd1 / pd2
48				margin = abs(out - args.output)
49				vco_is_better = vco < best[5] if args.low_vco else vco > best[5]
50				if ((vco * 1000) % (pd1 * pd2)):
51					continue
52				if margin < best_margin or (abs(margin - best_margin) < 1e-9 and vco_is_better):
53					best = (out, fbdiv, pd1, pd2, refdiv, vco)
54					best_margin = margin
55
56best_out, best_fbdiv, best_pd1, best_pd2, best_refdiv, best_vco = best
57
58if best[0] > 0:
59	cmake_output = \
60f"""target_compile_definitions({args.cmake_executable_name} PRIVATE
61	PLL_SYS_REFDIV={best_refdiv}
62	PLL_SYS_VCO_FREQ_HZ={int((args.input * 1_000_000) / best_refdiv * best_fbdiv)}
63	PLL_SYS_POSTDIV1={best_pd1}
64	PLL_SYS_POSTDIV2={best_pd2}
65	SYS_CLK_HZ={int((args.input * 1_000_000) / (best_refdiv * best_pd1 * best_pd2) * best_fbdiv)}
66)
67"""
68	if not args.cmake_only:
69		print("Requested: {} MHz".format(args.output))
70		print("Achieved:  {} MHz".format(best_out))
71		print("REFDIV:    {}".format(best_refdiv))
72		print("FBDIV:     {} (VCO = {} MHz)".format(best_fbdiv, args.input / best_refdiv * best_fbdiv))
73		print("PD1:       {}".format(best_pd1))
74		print("PD2:       {}".format(best_pd2))
75		if best_refdiv != 1:
76			print(
77				"\nThis requires a non-default REFDIV value.\n"
78				"Add the following to your CMakeLists.txt to apply the REFDIV:\n"
79			)
80		elif args.cmake or args.cmake_only:
81			print("")
82	if args.cmake or args.cmake_only or best_refdiv != 1:
83		print(cmake_output)
84else:
85	sys.exit("No solution found")
86