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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.
import threading
# Helper class to store incoming messages in a queue
class BulkDataQueue:
def __init__(self, mcu, msg_name, oid):
# Measurement storage (accessed from background thread)
self.lock = threading.Lock()
self.raw_samples = []
# Register callback with mcu
mcu.register_response(self._handle_data, msg_name, oid)
def _handle_data(self, params):
with self.lock:
self.raw_samples.append(params)
def pull_samples(self):
with self.lock:
raw_samples = self.raw_samples
self.raw_samples = []
return raw_samples
def clear_samples(self):
self.pull_samples()
# 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
MAX_BULK_MSG_SIZE = 52
# Handle common periodic chip status query responses
class ChipClockUpdater:
def __init__(self, clock_sync, bytes_per_sample):
self.clock_sync = clock_sync
self.bytes_per_sample = bytes_per_sample
self.samples_per_block = MAX_BULK_MSG_SIZE // bytes_per_sample
self.mcu = clock_sync.mcu
self.last_sequence = self.max_query_duration = 0
self.last_limit_count = 0
def get_last_sequence(self):
return self.last_sequence
def get_last_limit_count(self):
return self.last_limit_count
def clear_duration_filter(self):
self.max_query_duration = 1 << 31
def note_start(self, reqclock):
self.last_sequence = 0
self.last_limit_count = 0
self.clock_sync.reset(reqclock, 0)
self.clear_duration_filter()
def update_clock(self, params):
# Handle a status response message of the form:
# adxl345_status oid=x clock=x query_ticks=x next_sequence=x
# buffered=x fifo=x limit_count=x
fifo = params['fifo']
mcu_clock = self.mcu.clock32_to_clock64(params['clock'])
seq_diff = (params['next_sequence'] - self.last_sequence) & 0xffff
self.last_sequence += seq_diff
buffered = params['buffered']
lc_diff = (params['limit_count'] - self.last_limit_count) & 0xffff
self.last_limit_count += lc_diff
duration = params['query_ticks']
if duration > self.max_query_duration:
# Skip measurement as a high query time could skew clock tracking
self.max_query_duration = max(2 * self.max_query_duration,
self.mcu.seconds_to_clock(.000005))
return
self.max_query_duration = 2 * duration
msg_count = (self.last_sequence * self.samples_per_block
+ buffered // self.bytes_per_sample + fifo)
# The "chip clock" is the message counter plus .5 for average
# inaccuracy of query responses and plus .5 for assumed offset
# of hardware processing time.
chip_clock = msg_count + 1
self.clock_sync.update(mcu_clock + duration // 2, chip_clock)
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