Last active
July 1, 2021 14:16
-
-
Save andy-shev/06b084488b3629898121 to your computer and use it in GitHub Desktop.
Quark SoC SPI baudrate calculator
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#!/usr/bin/env python3 | |
# -*- coding: UTF-8 -*- | |
# vim: ts=4 sw=4 et ai si | |
import sys | |
import os | |
import operator | |
import math | |
import fractions | |
__author__ = "Andy Shevchenko" | |
__license__ = "GPL v2" | |
PROG = os.path.basename(sys.argv[0]) | |
FSYS = 200000000 | |
# | |
# Fssp = Fsys * DDS_CLK_RATE / 2**24 | |
# Baud rate = Fsclk = Fssp / (2 * (SCR + 1)) | |
# | |
# DDS_CLK_RATE either 2^n or 2^n / 5. | |
# SCR is in range 0 .. 255 | |
# | |
# Divisor = 5^i * 2^j * 2 * k | |
# i = [0, 1] i = 1 iff j = 0 or j > 3 | |
# j = [0, 23] j = 0 iff i = 1 | |
# k = [1, 256] | |
# Special case: j = 0, i = 1: Divisor = 2 / 5 | |
# | |
# Baud rate, DDS_CLK_RATE, SCR | |
TABLE = [ | |
[50000000, 8388608, 0], | |
[40020000, -1, -1], | |
[40000000, 6710886, 0], | |
[39980000, -1, -1], | |
[25000000, 4194304, 0], | |
[20000000, 6710886, 1], | |
[16667000, 8388608, 2], | |
[13333000, 6710886, 2], | |
[12500000, 2097152, 0], | |
[10000000, 8388608, 4], | |
[8000000, 6710886, 4], | |
[6250000, 4194304, 3], | |
[5000000, 4194304, 4], | |
[4350000, -1, -1], | |
[4000000, 6710886, 9], | |
[3333000, -1, -1], | |
[3140500, 524288, -1], | |
[3125000, 524288, 0], | |
[3109500, 524288, -1], | |
[2500000, 4194304, 9], | |
[2000000, 6710886, 19], | |
[1563000, 262144, 0], | |
[1250000, 2097152, 9], | |
[1006000, -1, -1], | |
[1000000, 4194304, 24], | |
[994000, -1, -1], | |
[800000, 6710886, 49], | |
[781250, 131072, 0], | |
[625000, 2097152, 19], | |
[500000, 4194304, 49], | |
[400000, 6710886, 99], | |
[390625, 65536, 0], | |
[250000, 4194304, 99], | |
[205313, 32768, -1], | |
[200000, 6710886, 199], | |
[195313, 32768, 0], | |
[185313, 32768, -1], | |
[125000, 1048576, 49], | |
[100700, -1, -1], | |
[100000, 2097152, 124], | |
[99300, -1, -1], | |
[50000, 1048576, 124], | |
[25000, 524288, 124], | |
[10066, 131072, -1], | |
[10016, 131072, 77], | |
[9966, 131072, -1], | |
[5065, 131072, -1], | |
[5040, 131072, 154], | |
[5015, 131072, -1], | |
[1007, 32768, -1], | |
[1002, 32768, 194], | |
[997, 32768, -1], | |
[69, -1, -1], | |
[7, -1, -1], | |
[2, -1, -1], | |
[1, -1, -1], | |
] | |
def idiv(a, b): | |
return int(a // b) | |
def go(fref, baud): | |
fr1 = idiv(fref, 2) | |
fr2 = idiv(fref * 2, 5) | |
q1 = idiv(fr1 + baud - 1, baud) | |
q2 = idiv(fr2 + baud - 1, baud) | |
q12 = q1 | |
q3 = idiv(fref + baud - 1, baud) | |
dds12 = 2 ** 23 | |
if q12 > 256: | |
# Use fls() | |
shift = int(math.ceil(math.log(q12, 2))) | |
if shift > 9: | |
q12 >>= shift - 9 | |
dds12 >>= shift - 9 | |
if q12 % 2: | |
q12 += 1 | |
# Use ffs() | |
while q12 % 2 == 0: | |
q12 >>= 1 | |
dds12 >>= 1 | |
arate1 = idiv(fr1, q1) | |
r1 = abs(baud - arate1) | |
dds2 = idiv(2 ** 24 * 2, 5) | |
arate2 = idiv(fr2, q2) | |
r2 = abs(baud - arate2) | |
div = 23 - int(math.log(dds12, 2)) | |
arate12 = idiv(fr1 >> div, q12) | |
r12 = abs(baud - arate12) | |
dds3 = idiv(2 ** 24, q3) | |
arate3 = idiv(fref * dds3, 2 ** 24) | |
r3 = abs(baud - arate3) | |
c1 = '%d, %d' % (q1, r1) | |
c12 = '%d, %d' % (q12, r12) | |
c2 = '' | |
c3 = '' | |
# if (r2 == 0 and r12 == 0 and dds2 > dds12) or (r2 and r2 >= r12) or q2 > 256: | |
if r2 >= r12 or q2 > 256: | |
arate = arate12 | |
dds = dds12 | |
q = q12 | |
r = r12 | |
else: | |
arate = arate2 | |
dds = dds2 | |
q = q2 | |
r = r2 | |
if q2 <= 256: | |
c2 = '%d, %d' % (q2, r2) | |
if fref / 80 >= baud: | |
if r3 < r: | |
arate = arate3 | |
dds = dds3 | |
q = 1 | |
r = r3 | |
c3 = '%d, %d' % (q3, r3) | |
choice = ' -> %06x, %d, %d' % (dds, q, r) | |
print("%8d(%8d): c1: %-12s c12: %-12s c2: %-12s c3: %-12s %s" % (baud, arate, c1, c12, c2, c3, choice)) | |
def usage(): | |
sys.stdout.write("Usage %s [CUSTOM_BAUD_RATE]\n" % PROG) | |
def toint(value): | |
try: | |
return int(value) | |
except ValueError: | |
usage() | |
raise SystemExit("Invalid argument") | |
def main(argv): | |
fref = FSYS / 2 | |
if len(argv) > 1: | |
custom = toint(argv[1]) | |
go(fref, custom) | |
else: | |
for item in TABLE: | |
go(fref, operator.itemgetter(0)(item)) | |
if __name__ == "__main__": | |
sys.exit(main(sys.argv)) |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment