clocksync: Rework clock synchronization algorithm
Instead of tracking the minimum frequency ever observed, attempt to track the actual frequency of the micro-controller (relative to the host clock). This improves the stability of the secondary mcu clocks when multiple mcus are configured. Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor
parent
387cab27bd
commit
d9fe4b6944
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@ -5,121 +5,120 @@
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# This file may be distributed under the terms of the GNU GPLv3 license.
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import logging, threading
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MAX_CLOCK_DRIFT = 0.000100
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COMM_TIMEOUT = 3.5
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RTT_AGE = .000010 / (60. * 60.)
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class ClockSync:
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def __init__(self, reactor):
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self.reactor = reactor
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self.serial = None
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self.queries_pending = 0
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self.status_timer = self.reactor.register_timer(self._status_event)
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self.status_cmd = None
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self.mcu_freq = 0.
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self.lock = threading.Lock()
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self.last_clock = 0
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self.last_clock_time = self.last_clock_time_min = 0.
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self.min_freq = self.max_freq = 0.
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self.min_half_rtt = 999999999.9
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self.min_half_rtt_time = 0.
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self.clock_est = self.prev_est = (0., 0, 0.)
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self.last_clock_fast = False
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def connect(self, serial):
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self.serial = serial
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# Load initial last_clock/last_clock_time
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msgparser = serial.msgparser
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self.mcu_freq = msgparser.get_constant_float('CLOCK_FREQ')
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# Load initial clock and frequency
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uptime_msg = msgparser.create_command('get_uptime')
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params = serial.send_with_response(uptime_msg, 'uptime')
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self.last_clock = (params['high'] << 32) | params['clock']
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self.last_clock_time = params['#receive_time']
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self.last_clock_time_min = params['#sent_time']
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self.mcu_freq = msgparser.get_constant_float('CLOCK_FREQ')
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self.min_freq = self.mcu_freq * (1. - MAX_CLOCK_DRIFT)
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self.max_freq = self.mcu_freq * (1. + MAX_CLOCK_DRIFT)
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self.last_clock = clock = (params['high'] << 32) | params['clock']
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new_time = .5 * (params['#sent_time'] + params['#receive_time'])
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self.clock_est = self.prev_est = (new_time, clock, self.mcu_freq)
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# Enable periodic get_status timer
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serial.register_callback(self._handle_status, 'status')
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self.status_cmd = msgparser.create_command('get_status')
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for i in range(8):
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params = serial.send_with_response(self.status_cmd, 'status')
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self._handle_status(params)
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self.reactor.pause(0.100)
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serial.register_callback(self._handle_status, 'status')
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self.reactor.update_timer(self.status_timer, self.reactor.NOW)
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def connect_file(self, serial, pace=False):
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self.serial = serial
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self.mcu_freq = serial.msgparser.get_constant_float('CLOCK_FREQ')
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est_freq = 1000000000000.
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freq = 1000000000000.
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if pace:
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est_freq = self.mcu_freq
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self.min_freq = self.max_freq = est_freq
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self.last_clock = 0
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self.last_clock_time = self.reactor.monotonic()
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serial.set_clock_est(
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self.min_freq, self.last_clock_time, self.last_clock)
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def stats(self, eventtime):
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return "last_clock=%d last_clock_time=%.3f" % (
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self.last_clock, self.last_clock_time)
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def is_active(self, eventtime):
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return self.queries_pending <= 4
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def calibrate_clock(self, print_time, eventtime):
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return (0., self.mcu_freq)
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def get_clock(self, eventtime):
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with self.lock:
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freq = self.mcu_freq
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serial.set_clock_est(freq, self.reactor.monotonic(), 0)
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# mcu clock querying
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def _status_event(self, eventtime):
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self.serial.send(self.status_cmd)
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return eventtime + 1.0
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def _handle_status(self, params):
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# Extend clock to 64bit
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clock32 = params['clock']
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last_clock = self.last_clock
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last_clock_time = self.last_clock_time
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min_freq = self.min_freq
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return int(last_clock + (eventtime - last_clock_time) * min_freq)
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clock = (last_clock & ~0xffffffff) | clock32
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if clock < last_clock:
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clock += 0x100000000
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self.last_clock = clock
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# Check if this is the best round-trip-time seen so far
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sent_time = params['#sent_time']
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if not sent_time:
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return
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receive_time = params['#receive_time']
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half_rtt = .5 * (receive_time - sent_time)
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aged_rtt = (sent_time - self.min_half_rtt_time) * RTT_AGE
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if half_rtt < self.min_half_rtt + aged_rtt:
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self.min_half_rtt = half_rtt
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self.min_half_rtt_time = sent_time
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logging.debug("new minimum rtt=%.6f (%d)", half_rtt, self.mcu_freq)
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# Calculate expected clock range from sent/receive time
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est_min_clock = self.get_clock(sent_time + self.min_half_rtt)
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est_max_clock = self.get_clock(receive_time - self.min_half_rtt)
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if clock >= est_min_clock and clock <= est_max_clock:
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# Sample inline with expectations
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return
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# Update estimated frequency based on latest sample
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if clock > est_max_clock:
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clock_fast = True
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new_time = receive_time - self.min_half_rtt
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else:
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clock_fast = False
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new_time = sent_time + self.min_half_rtt
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if clock_fast != self.last_clock_fast:
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self.prev_est = self.clock_est
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self.last_clock_fast = clock_fast
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new_freq = (self.prev_est[1] - clock) / (self.prev_est[0] - new_time)
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self.serial.set_clock_est(new_freq, new_time + 0.001, clock)
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self.clock_est = (new_time, clock, new_freq)
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# clock frequency conversions
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def print_time_to_clock(self, print_time):
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return int(print_time * self.mcu_freq)
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def clock_to_print_time(self, clock):
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return clock / self.mcu_freq
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def get_adjusted_freq(self):
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return self.mcu_freq
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# system time conversions
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def get_clock(self, eventtime):
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sample_time, clock, freq = self.clock_est
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return int(clock + (eventtime - sample_time) * freq)
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def estimated_print_time(self, eventtime):
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return self.clock_to_print_time(self.get_clock(eventtime))
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# misc commands
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def clock32_to_clock64(self, clock32):
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with self.lock:
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last_clock = self.last_clock
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clock_diff = (last_clock - clock32) & 0xffffffff
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if clock_diff & 0x80000000:
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return last_clock + 0x100000000 - clock_diff
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return last_clock - clock_diff
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def print_time_to_clock(self, print_time):
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return int(print_time * self.mcu_freq)
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def clock_to_print_time(self, clock):
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return clock / self.mcu_freq
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def estimated_print_time(self, eventtime):
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return self.clock_to_print_time(self.get_clock(eventtime))
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def get_adjusted_freq(self):
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return self.mcu_freq
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def _status_event(self, eventtime):
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self.queries_pending += 1
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self.serial.send(self.status_cmd)
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return eventtime + 1.0
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def _handle_status(self, params):
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self.queries_pending = 0
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sent_time = params['#sent_time']
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if not sent_time:
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return
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receive_time = params['#receive_time']
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clock = params['clock']
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with self.lock:
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# Extend clock to 64bit
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clock = (self.last_clock & ~0xffffffff) | clock
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if clock < self.last_clock:
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clock += 0x100000000
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# Calculate expected send time from clock and previous estimates
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clock_delta = clock - self.last_clock
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min_send_time = (self.last_clock_time_min
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+ clock_delta / self.max_freq)
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max_send_time = self.last_clock_time + clock_delta / self.min_freq
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# Calculate intersection of times
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min_time = max(min_send_time, sent_time)
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max_time = min(max_send_time, receive_time)
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if min_time > max_time:
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# No intersection - clock drift must be greater than expected
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new_min_freq, new_max_freq = self.min_freq, self.max_freq
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if min_send_time > receive_time:
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new_max_freq = (
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clock_delta / (receive_time - self.last_clock_time_min))
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else:
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new_min_freq = (
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clock_delta / (sent_time - self.last_clock_time))
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logging.warning(
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"High clock drift! Now %.0f:%.0f was %.0f:%.0f",
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new_min_freq, new_max_freq, self.min_freq, self.max_freq)
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self.min_freq, self.max_freq = new_min_freq, new_max_freq
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min_time, max_time = sent_time, receive_time
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# Update variables
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self.last_clock = clock
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self.last_clock_time = max_time
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self.last_clock_time_min = min_time
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self.serial.set_clock_est(self.min_freq, max_time + 0.001, clock)
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def is_active(self, eventtime):
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print_time = self.estimated_print_time(eventtime)
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last_clock_print_time = self.clock_to_print_time(self.last_clock)
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return print_time < last_clock_print_time + COMM_TIMEOUT
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def stats(self, eventtime):
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sample_time, clock, freq = self.clock_est
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return "freq=%d" % (freq,)
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def calibrate_clock(self, print_time, eventtime):
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return (0., self.mcu_freq)
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# Clock synching code for secondary MCUs (whose clocks are sync'ed to
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# a primary MCU)
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# Clock syncing code for secondary MCUs (whose clocks are sync'ed to a
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# primary MCU)
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class SecondarySync(ClockSync):
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def __init__(self, reactor, main_sync):
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ClockSync.__init__(self, reactor)
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@ -136,6 +135,7 @@ class SecondarySync(ClockSync):
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def connect_file(self, serial, pace=False):
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ClockSync.connect_file(self, serial, pace)
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self.clock_adj = (0., self.mcu_freq)
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# clock frequency conversions
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def print_time_to_clock(self, print_time):
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adjusted_offset, adjusted_freq = self.clock_adj
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return int((print_time - adjusted_offset) * adjusted_freq)
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@ -145,25 +145,22 @@ class SecondarySync(ClockSync):
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def get_adjusted_freq(self):
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adjusted_offset, adjusted_freq = self.clock_adj
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return adjusted_freq
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# misc commands
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def stats(self, eventtime):
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adjusted_offset, adjusted_freq = self.clock_adj
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return "%s adj=%d" % (ClockSync.stats(self, eventtime), adjusted_freq)
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def calibrate_clock(self, print_time, eventtime):
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#logging.debug("calibrate: %.3f: %.6f vs %.6f",
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# eventtime,
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# self.estimated_print_time(eventtime),
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# self.main_sync.estimated_print_time(eventtime))
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with self.main_sync.lock:
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ser_clock = self.main_sync.last_clock
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ser_clock_time = self.main_sync.last_clock_time
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ser_freq = self.main_sync.min_freq
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ser_time, ser_clock, ser_freq = self.main_sync.clock_est
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main_mcu_freq = self.main_sync.mcu_freq
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main_clock = (eventtime - ser_clock_time) * ser_freq + ser_clock
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main_clock = (eventtime - ser_time) * ser_freq + ser_clock
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print_time = max(print_time, main_clock / main_mcu_freq)
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main_sync_clock = (print_time + 2.) * main_mcu_freq
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sync_time = ser_clock_time + (main_sync_clock - ser_clock) / ser_freq
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main_sync_clock = (print_time + 4.) * main_mcu_freq
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sync_time = ser_time + (main_sync_clock - ser_clock) / ser_freq
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print_clock = self.print_time_to_clock(print_time)
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sync_clock = self.get_clock(sync_time)
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adjusted_freq = .5 * (sync_clock - print_clock)
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adjusted_freq = .25 * (sync_clock - print_clock)
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adjusted_offset = print_time - print_clock / adjusted_freq
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self.clock_adj = (adjusted_offset, adjusted_freq)
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