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# Micro-controller clock synchronization
#
# Copyright (C) 2016,2017 Kevin O'Connor <kevin@koconnor.net>
#
# This file may be distributed under the terms of the GNU GPLv3 license.
import logging, threading
COMM_TIMEOUT = 3.5
RTT_AGE = .000010 / (60. * 60.)
class ClockSync:
def __init__(self, reactor):
self.reactor = reactor
self.serial = None
self.status_timer = self.reactor.register_timer(self._status_event)
self.status_cmd = None
self.mcu_freq = 0.
self.last_clock = 0
self.min_half_rtt = 999999999.9
self.min_half_rtt_time = 0.
self.clock_est = self.prev_est = (0., 0, 0.)
self.min_freq = 0.
self.last_clock_fast = False
def connect(self, serial):
self.serial = serial
msgparser = serial.msgparser
self.mcu_freq = msgparser.get_constant_float('CLOCK_FREQ')
# Load initial clock and frequency
uptime_msg = msgparser.create_command('get_uptime')
params = serial.send_with_response(uptime_msg, 'uptime')
self.last_clock = clock = (params['high'] << 32) | params['clock']
new_time = .5 * (params['#sent_time'] + params['#receive_time'])
self.clock_est = self.prev_est = (new_time, clock, self.mcu_freq)
self.min_freq = self.mcu_freq
# Enable periodic get_status timer
self.status_cmd = msgparser.create_command('get_status')
for i in range(8):
params = serial.send_with_response(self.status_cmd, 'status')
self._handle_status(params)
self.reactor.pause(0.100)
serial.register_callback(self._handle_status, 'status')
self.reactor.update_timer(self.status_timer, self.reactor.NOW)
def connect_file(self, serial, pace=False):
self.serial = serial
self.mcu_freq = serial.msgparser.get_constant_float('CLOCK_FREQ')
freq = 1000000000000.
if pace:
freq = self.mcu_freq
serial.set_clock_est(freq, self.reactor.monotonic(), 0)
# mcu clock querying
def _status_event(self, eventtime):
self.serial.send(self.status_cmd)
return eventtime + 1.0
def _handle_status(self, params):
# Extend clock to 64bit
clock32 = params['clock']
last_clock = self.last_clock
clock = (last_clock & ~0xffffffff) | clock32
if clock < last_clock:
clock += 0x100000000
self.last_clock = clock
# Check if this is the best round-trip-time seen so far
sent_time = params['#sent_time']
if not sent_time:
return
receive_time = params['#receive_time']
half_rtt = .5 * (receive_time - sent_time)
aged_rtt = (sent_time - self.min_half_rtt_time) * RTT_AGE
if half_rtt < self.min_half_rtt + aged_rtt:
self.min_half_rtt = half_rtt
self.min_half_rtt_time = sent_time
logging.debug("new minimum rtt=%.6f (%d)", half_rtt, self.mcu_freq)
# Calculate expected clock range from sent/receive time
est_min_clock = self.get_clock(sent_time + self.min_half_rtt)
est_max_clock = self.get_clock(receive_time - self.min_half_rtt)
if clock >= est_min_clock and clock <= est_max_clock:
# Sample inline with expectations
return
# Update estimated frequency based on latest sample
if clock > est_max_clock:
clock_fast = True
new_time = receive_time - self.min_half_rtt
else:
clock_fast = False
new_time = sent_time + self.min_half_rtt
if clock_fast != self.last_clock_fast:
self.prev_est = self.clock_est
self.last_clock_fast = clock_fast
new_freq = (self.prev_est[1] - clock) / (self.prev_est[0] - new_time)
self.min_freq = min(self.min_freq, new_freq)
self.serial.set_clock_est(
self.min_freq, new_time + self.min_half_rtt + 0.001, clock)
self.clock_est = (new_time, clock, new_freq)
# clock frequency conversions
def print_time_to_clock(self, print_time):
return int(print_time * self.mcu_freq)
def clock_to_print_time(self, clock):
return clock / self.mcu_freq
def get_adjusted_freq(self):
return self.mcu_freq
# system time conversions
def get_clock(self, eventtime):
sample_time, clock, freq = self.clock_est
return int(clock + (eventtime - sample_time) * freq)
def estimated_print_time(self, eventtime):
return self.clock_to_print_time(self.get_clock(eventtime))
# misc commands
def clock32_to_clock64(self, clock32):
last_clock = self.last_clock
clock_diff = (last_clock - clock32) & 0xffffffff
if clock_diff & 0x80000000:
return last_clock + 0x100000000 - clock_diff
return last_clock - clock_diff
def is_active(self, eventtime):
print_time = self.estimated_print_time(eventtime)
last_clock_print_time = self.clock_to_print_time(self.last_clock)
return print_time < last_clock_print_time + COMM_TIMEOUT
def stats(self, eventtime):
sample_time, clock, freq = self.clock_est
return "freq=%d" % (freq,)
def calibrate_clock(self, print_time, eventtime):
return (0., self.mcu_freq)
# Clock syncing code for secondary MCUs (whose clocks are sync'ed to a
# primary MCU)
class SecondarySync(ClockSync):
def __init__(self, reactor, main_sync):
ClockSync.__init__(self, reactor)
self.main_sync = main_sync
self.clock_adj = (0., 0.)
def connect(self, serial):
ClockSync.connect(self, serial)
self.clock_adj = (0., self.mcu_freq)
curtime = self.reactor.monotonic()
main_print_time = self.main_sync.estimated_print_time(curtime)
local_print_time = self.estimated_print_time(curtime)
self.clock_adj = (main_print_time - local_print_time, self.mcu_freq)
self.calibrate_clock(0., curtime)
def connect_file(self, serial, pace=False):
ClockSync.connect_file(self, serial, pace)
self.clock_adj = (0., self.mcu_freq)
# clock frequency conversions
def print_time_to_clock(self, print_time):
adjusted_offset, adjusted_freq = self.clock_adj
return int((print_time - adjusted_offset) * adjusted_freq)
def clock_to_print_time(self, clock):
adjusted_offset, adjusted_freq = self.clock_adj
return clock / adjusted_freq + adjusted_offset
def get_adjusted_freq(self):
adjusted_offset, adjusted_freq = self.clock_adj
return adjusted_freq
# misc commands
def stats(self, eventtime):
adjusted_offset, adjusted_freq = self.clock_adj
return "%s adj=%d" % (ClockSync.stats(self, eventtime), adjusted_freq)
def calibrate_clock(self, print_time, eventtime):
ser_time, ser_clock, ser_freq = self.main_sync.clock_est
main_mcu_freq = self.main_sync.mcu_freq
main_clock = (eventtime - ser_time) * ser_freq + ser_clock
print_time = max(print_time, main_clock / main_mcu_freq)
main_sync_clock = (print_time + 4.) * main_mcu_freq
sync_time = ser_time + (main_sync_clock - ser_clock) / ser_freq
print_clock = self.print_time_to_clock(print_time)
sync_clock = self.get_clock(sync_time)
adjusted_freq = .25 * (sync_clock - print_clock)
adjusted_offset = print_time - print_clock / adjusted_freq
self.clock_adj = (adjusted_offset, adjusted_freq)
return self.clock_adj
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