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# Tools for reading bulk sensor data from the mcu
#
# Copyright (C) 2020-2023 Kevin O'Connor <kevin@koconnor.net>
#
# This file may be distributed under the terms of the GNU GPLv3 license.
# Helper class for chip clock synchronization via linear regression
class ClockSyncRegression:
def __init__(self, mcu, chip_clock_smooth, decay = 1. / 20.):
self.mcu = mcu
self.chip_clock_smooth = chip_clock_smooth
self.decay = decay
self.last_chip_clock = self.last_exp_mcu_clock = 0.
self.mcu_clock_avg = self.mcu_clock_variance = 0.
self.chip_clock_avg = self.chip_clock_covariance = 0.
def reset(self, mcu_clock, chip_clock):
self.mcu_clock_avg = self.last_mcu_clock = mcu_clock
self.chip_clock_avg = chip_clock
self.mcu_clock_variance = self.chip_clock_covariance = 0.
self.last_chip_clock = self.last_exp_mcu_clock = 0.
def update(self, mcu_clock, chip_clock):
# Update linear regression
decay = self.decay
diff_mcu_clock = mcu_clock - self.mcu_clock_avg
self.mcu_clock_avg += decay * diff_mcu_clock
self.mcu_clock_variance = (1. - decay) * (
self.mcu_clock_variance + diff_mcu_clock**2 * decay)
diff_chip_clock = chip_clock - self.chip_clock_avg
self.chip_clock_avg += decay * diff_chip_clock
self.chip_clock_covariance = (1. - decay) * (
self.chip_clock_covariance + diff_mcu_clock*diff_chip_clock*decay)
def set_last_chip_clock(self, chip_clock):
base_mcu, base_chip, inv_cfreq = self.get_clock_translation()
self.last_chip_clock = chip_clock
self.last_exp_mcu_clock = base_mcu + (chip_clock-base_chip) * inv_cfreq
def get_clock_translation(self):
inv_chip_freq = self.mcu_clock_variance / self.chip_clock_covariance
if not self.last_chip_clock:
return self.mcu_clock_avg, self.chip_clock_avg, inv_chip_freq
# Find mcu clock associated with future chip_clock
s_chip_clock = self.last_chip_clock + self.chip_clock_smooth
scdiff = s_chip_clock - self.chip_clock_avg
s_mcu_clock = self.mcu_clock_avg + scdiff * inv_chip_freq
# Calculate frequency to converge at future point
mdiff = s_mcu_clock - self.last_exp_mcu_clock
s_inv_chip_freq = mdiff / self.chip_clock_smooth
return self.last_exp_mcu_clock, self.last_chip_clock, s_inv_chip_freq
def get_time_translation(self):
base_mcu, base_chip, inv_cfreq = self.get_clock_translation()
clock_to_print_time = self.mcu.clock_to_print_time
base_time = clock_to_print_time(base_mcu)
inv_freq = clock_to_print_time(base_mcu + inv_cfreq) - base_time
return base_time, base_chip, inv_freq
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