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"""
This is an auxiliary script that is used to compute valid PLL values to set
the CPU frequency to a given value. The algorithm here appears as C code
for the machine.freq() function.
"""
from __future__ import print_function
def close_int(x):
return abs(x - round(x)) < 0.01
# original version that requires N/M to be an integer (for simplicity)
def compute_pll(hse, sys):
for P in (2, 4, 6, 8): # allowed values of P
Q = sys * P / 48
NbyM = sys * P / hse
# N/M and Q must be integers
if not (close_int(NbyM) and close_int(Q)):
continue
# VCO_OUT must be between 192MHz and 432MHz
if not (192 <= hse * NbyM <= 432):
continue
# compute M
M = int(192 // NbyM)
while hse > 2 * M or NbyM * M < 192:
M += 1
# VCO_IN must be between 1MHz and 2MHz (2MHz recommended)
if not (M <= hse):
continue
# compute N
N = NbyM * M
# N and Q are restricted
if not (192 <= N <= 432 and 2 <= Q <= 15):
continue
# found valid values
assert NbyM == N // M
return (M, N, P, Q)
# no valid values found
return None
# improved version that doesn't require N/M to be an integer
def compute_pll2(hse, sys):
# Loop over the allowed values of P, looking for a valid PLL configuration
# that gives the desired "sys" frequency. We use floats for P to force
# floating point arithmetic on Python 2.
for P in (2.0, 4.0, 6.0, 8.0):
Q = sys * P / 48
# Q must be an integer in a set range
if not (close_int(Q) and 2 <= Q <= 15):
continue
NbyM = sys * P / hse
# VCO_OUT must be between 192MHz and 432MHz
if not (192 <= hse * NbyM <= 432):
continue
# compute M
M = 192 // NbyM # starting value
while hse > 2 * M or NbyM * M < 192 or not close_int(NbyM * M):
M += 1
# VCO_IN must be between 1MHz and 2MHz (2MHz recommended)
if not (M <= hse):
continue
# compute N
N = NbyM * M
# N must be an integer
if not close_int(N):
continue
# N is restricted
if not (192 <= N <= 432):
continue
# found valid values
return (M, N, P, Q)
# no valid values found
return None
def compute_derived(hse, pll):
M, N, P, Q = pll
vco_in = hse / M
vco_out = hse * N / M
pllck = hse / M * N / P
pll48ck = hse / M * N / Q
return (vco_in, vco_out, pllck, pll48ck)
def verify_pll(hse, pll):
M, N, P, Q = pll
vco_in, vco_out, pllck, pll48ck = compute_derived(hse, pll)
# verify ints
assert close_int(M)
assert close_int(N)
assert close_int(P)
assert close_int(Q)
# verify range
assert 2 <= M <= 63
assert 192 <= N <= 432
assert P in (2, 4, 6, 8)
assert 2 <= Q <= 15
assert 1 <= vco_in <= 2
assert 192 <= vco_out <= 432
def generate_c_table(hse, valid_plls):
valid_plls = valid_plls + [(16, (0, 0, 2, 0))]
if hse < 16:
valid_plls.append((hse, (1, 0, 2, 0)))
valid_plls.sort()
print("// (M, P/2-1, SYS) values for %u MHz HSE" % hse)
print("static const uint16_t pll_freq_table[%u] = {" % len(valid_plls))
for sys, (M, N, P, Q) in valid_plls:
print(" (%u << 10) | (%u << 8) | %u," % (M, P // 2 - 1, sys))
print("};")
def print_table(hse, valid_plls):
print("HSE =", hse, "MHz")
print("sys : M N P Q : VCO_IN VCO_OUT PLLCK PLL48CK")
out_format = "%3u : %2u %.1f %.2f %.2f : %5.2f %6.2f %6.2f %6.2f"
for sys, pll in valid_plls:
print(out_format % ((sys,) + pll + compute_derived(hse, pll)))
print("found %u valid configurations" % len(valid_plls))
def main():
global out_format
# parse input args
import sys
argv = sys.argv[1:]
c_table = False
if argv[0] == '-c':
c_table = True
argv.pop(0)
if len(argv) != 1:
print("usage: pllvalues.py [-c] <hse in MHz>")
sys.exit(1)
if argv[0].startswith("file:"):
# extract HSE_VALUE from header file
with open(argv[0][5:]) as f:
for line in f:
line = line.strip()
if line.startswith("#define") and line.find("HSE_VALUE") != -1:
idx_start = line.find("((uint32_t)") + 11
idx_end = line.find(")", idx_start)
hse = int(line[idx_start:idx_end]) // 1000000
break
else:
raise ValueError("%s does not contain a definition of HSE_VALUE" % argv[0])
else:
# HSE given directly as an integer
hse = int(argv[0])
valid_plls = []
for sysclk in range(1, 217):
pll = compute_pll2(hse, sysclk)
if pll is not None:
verify_pll(hse, pll)
valid_plls.append((sysclk, pll))
if c_table:
generate_c_table(hse, valid_plls)
else:
print_table(hse, valid_plls)
if __name__ == "__main__":
main()
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