Merge "Upgrade bazel to 5.0.0"
diff --git a/aos/events/event_loop.h b/aos/events/event_loop.h
index 11368ae..e810e3f 100644
--- a/aos/events/event_loop.h
+++ b/aos/events/event_loop.h
@@ -407,7 +407,9 @@
   // Returns the name of the underlying queue.
   const Channel *channel() const { return sender_->channel(); }
 
+  // TODO(austin): Deprecate the operator bool.
   operator bool() const { return sender_ ? true : false; }
+  bool valid() const { return static_cast<bool>(sender_); }
 
   // Returns the time_points that the last message was sent at.
   aos::monotonic_clock::time_point monotonic_sent_time() const {
diff --git a/aos/events/event_scheduler.cc b/aos/events/event_scheduler.cc
index c06638c..97e0946 100644
--- a/aos/events/event_scheduler.cc
+++ b/aos/events/event_scheduler.cc
@@ -66,20 +66,32 @@
 }
 
 void EventScheduler::RunOnRun() {
-  for (std::function<void()> &on_run : on_run_) {
-    on_run();
+  while (!on_run_.empty()) {
+    std::function<void()> fn = std::move(*on_run_.begin());
+    on_run_.erase(on_run_.begin());
+    fn();
   }
-  on_run_.clear();
 }
 
-void EventScheduler::RunOnStartup() {
-  for (size_t i = 0; i < on_startup_.size(); ++i) {
-    on_startup_[i]();
+void EventScheduler::RunOnStartup() noexcept {
+  while (!on_startup_.empty()) {
+    std::function<void()> fn = std::move(*on_startup_.begin());
+    on_startup_.erase(on_startup_.begin());
+    fn();
   }
-  on_startup_.clear();
 }
 
-void EventScheduler::RunStarted() { started_(); }
+void EventScheduler::RunStarted() {
+  if (started_) {
+    started_();
+  }
+}
+
+void EventScheduler::RunStopped() {
+  if (stopped_) {
+    stopped_();
+  }
+}
 
 std::ostream &operator<<(std::ostream &stream,
                          const aos::distributed_clock::time_point &now) {
@@ -119,6 +131,7 @@
       rebooted.emplace_back(node_index);
       CHECK_EQ(schedulers_[node_index]->boot_count() + 1,
                times[node_index].boot);
+      schedulers_[node_index]->RunStopped();
       schedulers_[node_index]->Shutdown();
     }
   }
@@ -144,6 +157,7 @@
 void EventSchedulerScheduler::RunFor(distributed_clock::duration duration) {
   distributed_clock::time_point end_time = now_ + duration;
   logging::ScopedLogRestorer prev_logger;
+  RunOnStartup();
   RunOnRun();
 
   // Run all the sub-event-schedulers.
@@ -191,10 +205,13 @@
   }
 
   now_ = end_time;
+
+  RunStopped();
 }
 
 void EventSchedulerScheduler::Run() {
   logging::ScopedLogRestorer prev_logger;
+  RunOnStartup();
   RunOnRun();
   // Run all the sub-event-schedulers.
   while (is_running_) {
@@ -232,6 +249,8 @@
   }
 
   is_running_ = false;
+
+  RunStopped();
 }
 
 std::tuple<distributed_clock::time_point, EventScheduler *>
@@ -261,4 +280,17 @@
   return std::make_tuple(min_event_time, min_scheduler);
 }
 
+void EventSchedulerScheduler::TemporarilyStopAndRun(std::function<void()> fn) {
+  const bool was_running = is_running_;
+  if (is_running_) {
+    is_running_ = false;
+    RunStopped();
+  }
+  fn();
+  if (was_running) {
+    RunOnStartup();
+    RunOnRun();
+  }
+}
+
 }  // namespace aos
diff --git a/aos/events/event_scheduler.h b/aos/events/event_scheduler.h
index 55c1cf8..b64728c 100644
--- a/aos/events/event_scheduler.h
+++ b/aos/events/event_scheduler.h
@@ -126,7 +126,12 @@
     started_ = std::move(callback);
   }
 
+  void set_stopped(std::function<void()> callback) {
+    stopped_ = std::move(callback);
+  }
+
   std::function<void()> started_;
+  std::function<void()> stopped_;
   std::function<void()> on_shutdown_;
 
   Token InvalidToken() { return events_list_.end(); }
@@ -138,10 +143,12 @@
   void RunOnRun();
 
   // Runs the OnStartup callbacks.
-  void RunOnStartup();
+  void RunOnStartup() noexcept;
 
   // Runs the Started callback.
   void RunStarted();
+  // Runs the Started callback.
+  void RunStopped();
 
   // Returns true if events are being handled.
   inline bool is_running() const;
@@ -283,6 +290,13 @@
     }
   }
 
+  void RunStopped() {
+    CHECK(!is_running_);
+    for (EventScheduler *scheduler : schedulers_) {
+      scheduler->RunStopped();
+    }
+  }
+
   void SetTimeConverter(TimeConverter *time_converter) {
     time_converter->set_reboot_found(
         [this](distributed_clock::time_point reboot_time,
@@ -294,6 +308,11 @@
         });
   }
 
+  // Runs the provided callback now.  Stops everything, runs the callback, then
+  // starts it all up again.  This lets us do operations like starting and
+  // stopping applications while running.
+  void TemporarilyStopAndRun(std::function<void()> fn);
+
  private:
   // Handles running the OnRun functions.
   void RunOnRun() {
diff --git a/aos/events/logging/log_reader.cc b/aos/events/logging/log_reader.cc
index e58ccd2..4e89a0e 100644
--- a/aos/events/logging/log_reader.cc
+++ b/aos/events/logging/log_reader.cc
@@ -39,6 +39,13 @@
     time_estimation_buffer_seconds, 2.0,
     "The time to buffer ahead in the log file to accurately reconstruct time.");
 
+DEFINE_string(
+    start_time, "",
+    "If set, start at this point in time in the log on the realtime clock.");
+DEFINE_string(
+    end_time, "",
+    "If set, end at this point in time in the log on the realtime clock.");
+
 namespace aos {
 namespace configuration {
 // We don't really want to expose this publicly, but log reader doesn't really
@@ -131,6 +138,79 @@
 using message_bridge::RemoteMessage;
 }  // namespace
 
+// Class to manage triggering events on the RT clock while replaying logs. Since
+// the RT clock can only change when we get a message, we only need to update
+// our timers when new messages are read.
+class EventNotifier {
+ public:
+  EventNotifier(EventLoop *event_loop, std::function<void()> fn,
+                std::string_view name,
+                realtime_clock::time_point realtime_event_time)
+      : event_loop_(event_loop),
+        fn_(std::move(fn)),
+        realtime_event_time_(realtime_event_time) {
+    CHECK(event_loop_);
+    event_timer_ = event_loop->AddTimer([this]() { HandleTime(); });
+
+    if (event_loop_->node() != nullptr) {
+      event_timer_->set_name(
+          absl::StrCat(event_loop_->node()->name()->string_view(), "_", name));
+    } else {
+      event_timer_->set_name(name);
+    }
+  }
+
+  ~EventNotifier() { event_timer_->Disable(); }
+
+  // Returns the event trigger time.
+  realtime_clock::time_point realtime_event_time() const {
+    return realtime_event_time_;
+  }
+
+  // Observes the next message and potentially calls the callback or updates the
+  // timer.
+  void ObserveNextMessage(monotonic_clock::time_point monotonic_message_time,
+                          realtime_clock::time_point realtime_message_time) {
+    if (realtime_message_time < realtime_event_time_) {
+      return;
+    }
+    if (called_) {
+      return;
+    }
+
+    // Move the callback wakeup time to the correct time (or make it now if
+    // there's a gap in time) now that we know it is before the next
+    // message.
+    const monotonic_clock::time_point candidate_monotonic =
+        (realtime_event_time_ - realtime_message_time) + monotonic_message_time;
+    const monotonic_clock::time_point monotonic_now =
+        event_loop_->monotonic_now();
+    if (candidate_monotonic < monotonic_now) {
+      // Whops, time went backwards.  Just do it now.
+      HandleTime();
+    } else {
+      event_timer_->Setup(candidate_monotonic);
+    }
+  }
+
+ private:
+  void HandleTime() {
+    if (!called_) {
+      called_ = true;
+      fn_();
+    }
+  }
+
+  EventLoop *event_loop_ = nullptr;
+  TimerHandler *event_timer_ = nullptr;
+  std::function<void()> fn_;
+
+  const realtime_clock::time_point realtime_event_time_ =
+      realtime_clock::min_time;
+
+  bool called_ = false;
+};
+
 LogReader::LogReader(std::string_view filename,
                      const Configuration *replay_configuration)
     : LogReader(SortParts({std::string(filename)}), replay_configuration) {}
@@ -139,6 +219,9 @@
                      const Configuration *replay_configuration)
     : log_files_(std::move(log_files)),
       replay_configuration_(replay_configuration) {
+  SetStartTime(FLAGS_start_time);
+  SetEndTime(FLAGS_end_time);
+
   CHECK_GT(log_files_.size(), 0u);
   {
     // Validate that we have the same config everwhere.  This will be true if
@@ -329,8 +412,15 @@
 
   VLOG(1) << "Starting " << MaybeNodeName(node()) << "at time "
           << monotonic_start_time(boot_count());
-  for (size_t i = 0; i < on_starts_.size(); ++i) {
-    on_starts_[i]();
+  auto fn = [this]() {
+    for (size_t i = 0; i < on_starts_.size(); ++i) {
+      on_starts_[i]();
+    }
+  };
+  if (event_loop_factory_) {
+    event_loop_factory_->AllowApplicationCreationDuring(std::move(fn));
+  } else {
+    fn();
   }
   stopped_ = false;
   started_ = true;
@@ -358,12 +448,19 @@
 void LogReader::State::RunOnEnd() {
   VLOG(1) << "Ending " << MaybeNodeName(node()) << "at time "
           << monotonic_start_time(boot_count());
-  for (size_t i = 0; i < on_ends_.size(); ++i) {
-    on_ends_[i]();
+  auto fn = [this]() {
+    for (size_t i = 0; i < on_ends_.size(); ++i) {
+      on_ends_[i]();
+    }
+  };
+  if (event_loop_factory_) {
+    event_loop_factory_->AllowApplicationCreationDuring(std::move(fn));
+  } else {
+    fn();
   }
 
   stopped_ = true;
-  started_ = false;
+  started_ = true;
 }
 
 void LogReader::Register() {
@@ -397,7 +494,8 @@
         node);
     State *state = states_[node_index].get();
     state->SetNodeEventLoopFactory(
-        event_loop_factory_->GetNodeEventLoopFactory(node));
+        event_loop_factory_->GetNodeEventLoopFactory(node),
+        event_loop_factory_);
 
     state->SetChannelCount(logged_configuration()->channels()->size());
     timestamp_mappers.emplace_back(state->timestamp_mapper());
@@ -489,6 +587,11 @@
 
 void LogReader::Register(SimulatedEventLoopFactory *event_loop_factory) {
   RegisterWithoutStarting(event_loop_factory);
+  StartAfterRegister(event_loop_factory);
+}
+
+void LogReader::StartAfterRegister(
+    SimulatedEventLoopFactory *event_loop_factory) {
   // We want to start the log file at the last start time of the log files
   // from all the nodes.  Compute how long each node's simulation needs to run
   // to move time to this point.
@@ -588,6 +691,10 @@
   State *state =
       states_[configuration::GetNodeIndex(configuration(), node)].get();
 
+  if (!event_loop) {
+    state->ClearTimeFlags();
+  }
+
   state->set_event_loop(event_loop);
 
   // We don't run timing reports when trying to print out logged data, because
@@ -889,7 +996,7 @@
                 << "is on the next boot, " << next_time << " now is "
                 << state->monotonic_now();
         CHECK(event_loop_factory_);
-        state->RunOnEnd();
+        state->NotifyLogfileEnd();
         return;
       }
       VLOG(1) << "Scheduling " << MaybeNodeName(state->event_loop()->node())
@@ -900,7 +1007,7 @@
     } else {
       VLOG(1) << MaybeNodeName(state->event_loop()->node())
               << "No next message, scheduling shutdown";
-      state->RunOnEnd();
+      state->NotifyLogfileEnd();
       // Set a timer up immediately after now to die. If we don't do this,
       // then the senders waiting on the message we just read will never get
       // called.
@@ -917,7 +1024,13 @@
 
   if (state->OldestMessageTime() != BootTimestamp::max_time()) {
     state->set_startup_timer(
-        event_loop->AddTimer([state]() { state->RunOnStart(); }));
+        event_loop->AddTimer([state]() { state->NotifyLogfileStart(); }));
+    if (start_time_ != realtime_clock::min_time) {
+      state->SetStartTimeFlag(start_time_);
+    }
+    if (end_time_ != realtime_clock::max_time) {
+      state->SetEndTimeFlag(end_time_);
+    }
     event_loop->OnRun([state]() {
       BootTimestamp next_time = state->OldestMessageTime();
       CHECK_EQ(next_time.boot, state->boot_count());
@@ -927,6 +1040,40 @@
   }
 }
 
+void LogReader::SetEndTime(std::string end_time) {
+  if (end_time.empty()) {
+    SetEndTime(realtime_clock::max_time);
+  } else {
+    std::optional<aos::realtime_clock::time_point> parsed_end_time =
+        aos::realtime_clock::FromString(end_time);
+    CHECK(parsed_end_time) << ": Failed to parse end time '" << end_time
+                           << "'.  Expected a date in the format of "
+                              "2021-01-15_15-30-35.000000000.";
+    SetEndTime(*parsed_end_time);
+  }
+}
+
+void LogReader::SetEndTime(realtime_clock::time_point end_time) {
+  end_time_ = end_time;
+}
+
+void LogReader::SetStartTime(std::string start_time) {
+  if (start_time.empty()) {
+    SetStartTime(realtime_clock::min_time);
+  } else {
+    std::optional<aos::realtime_clock::time_point> parsed_start_time =
+        aos::realtime_clock::FromString(start_time);
+    CHECK(parsed_start_time) << ": Failed to parse start time '" << start_time
+                             << "'.  Expected a date in the format of "
+                                "2021-01-15_15-30-35.000000000.";
+    SetStartTime(*parsed_start_time);
+  }
+}
+
+void LogReader::SetStartTime(realtime_clock::time_point start_time) {
+  start_time_ = start_time;
+}
+
 void LogReader::Deregister() {
   // Make sure that things get destroyed in the correct order, rather than
   // relying on getting the order correct in the class definition.
@@ -1312,8 +1459,10 @@
 }
 
 void LogReader::State::SetNodeEventLoopFactory(
-    NodeEventLoopFactory *node_event_loop_factory) {
+    NodeEventLoopFactory *node_event_loop_factory,
+    SimulatedEventLoopFactory *event_loop_factory) {
   node_event_loop_factory_ = node_event_loop_factory;
+  event_loop_factory_ = event_loop_factory;
 }
 
 void LogReader::State::SetChannelCount(size_t count) {
@@ -1670,7 +1819,7 @@
   return result;
 }
 
-BootTimestamp LogReader::State::OldestMessageTime() const {
+BootTimestamp LogReader::State::OldestMessageTime() {
   if (timestamp_mapper_ == nullptr) {
     return BootTimestamp::max_time();
   }
@@ -1680,6 +1829,12 @@
   }
   VLOG(2) << MaybeNodeName(node()) << "oldest message at "
           << result_ptr->monotonic_event_time.time;
+
+  if (result_ptr->monotonic_event_time.boot == boot_count()) {
+    ObserveNextMessage(result_ptr->monotonic_event_time.time,
+                       result_ptr->realtime_event_time);
+  }
+
   return result_ptr->monotonic_event_time;
 }
 
@@ -1692,11 +1847,12 @@
 
 void LogReader::State::Deregister() {
   if (started_ && !stopped_) {
-    RunOnEnd();
+    NotifyLogfileEnd();
   }
   for (size_t i = 0; i < channels_.size(); ++i) {
     channels_[i].reset();
   }
+  ClearTimeFlags();
   channel_timestamp_loggers_.clear();
   timestamp_loggers_.clear();
   event_loop_unique_ptr_.reset();
@@ -1705,5 +1861,75 @@
   node_event_loop_factory_ = nullptr;
 }
 
+void LogReader::State::SetStartTimeFlag(realtime_clock::time_point start_time) {
+  if (start_time != realtime_clock::min_time) {
+    start_event_notifier_ = std::make_unique<EventNotifier>(
+        event_loop_, [this]() { NotifyFlagStart(); }, "flag_start", start_time);
+  }
+}
+
+void LogReader::State::SetEndTimeFlag(realtime_clock::time_point end_time) {
+  if (end_time != realtime_clock::max_time) {
+    end_event_notifier_ = std::make_unique<EventNotifier>(
+        event_loop_, [this]() { NotifyFlagEnd(); }, "flag_end", end_time);
+  }
+}
+
+void LogReader::State::ObserveNextMessage(
+    monotonic_clock::time_point monotonic_event,
+    realtime_clock::time_point realtime_event) {
+  if (start_event_notifier_) {
+    start_event_notifier_->ObserveNextMessage(monotonic_event, realtime_event);
+  }
+  if (end_event_notifier_) {
+    end_event_notifier_->ObserveNextMessage(monotonic_event, realtime_event);
+  }
+}
+
+void LogReader::State::ClearTimeFlags() {
+  start_event_notifier_.reset();
+  end_event_notifier_.reset();
+}
+
+void LogReader::State::NotifyLogfileStart() {
+  if (start_event_notifier_) {
+    if (start_event_notifier_->realtime_event_time() >
+        realtime_start_time(boot_count())) {
+      VLOG(1) << "Skipping, " << start_event_notifier_->realtime_event_time()
+              << " > " << realtime_start_time(boot_count());
+      return;
+    }
+  }
+  if (found_last_message_) {
+    VLOG(1) << "Last message already found, bailing";
+    return;
+  }
+  RunOnStart();
+}
+
+void LogReader::State::NotifyFlagStart() {
+  if (start_event_notifier_->realtime_event_time() >=
+      realtime_start_time(boot_count())) {
+    RunOnStart();
+  }
+}
+
+void LogReader::State::NotifyLogfileEnd() {
+  if (found_last_message_) {
+    return;
+  }
+
+  if (!stopped_ && started_) {
+    RunOnEnd();
+  }
+}
+
+void LogReader::State::NotifyFlagEnd() {
+  if (!stopped_ && started_) {
+    RunOnEnd();
+    SetFoundLastMessage(true);
+  }
+}
+
 }  // namespace logger
 }  // namespace aos
diff --git a/aos/events/logging/log_reader.h b/aos/events/logging/log_reader.h
index 3eebba7..9bfc90a 100644
--- a/aos/events/logging/log_reader.h
+++ b/aos/events/logging/log_reader.h
@@ -23,6 +23,8 @@
 namespace aos {
 namespace logger {
 
+class EventNotifier;
+
 // We end up with one of the following 3 log file types.
 //
 // Single node logged as the source node.
@@ -73,10 +75,20 @@
   // below, but can be anything as long as the locations needed to send
   // everything are available.
   void Register(SimulatedEventLoopFactory *event_loop_factory);
+
   // Registers all the callbacks to send the log file data out to an event loop
   // factory.  This does not start replaying or change the current distributed
   // time of the factory.  It does change the monotonic clocks to be right.
   void RegisterWithoutStarting(SimulatedEventLoopFactory *event_loop_factory);
+  // Runs the log until the last start time.  Register above is defined as:
+  // Register(...) {
+  //   RegisterWithoutStarting
+  //   StartAfterRegister
+  // }
+  // This should generally be considered as a stepping stone to convert from
+  // Register() to RegisterWithoutStarting() incrementally.
+  void StartAfterRegister(SimulatedEventLoopFactory *event_loop_factory);
+
   // Creates an SimulatedEventLoopFactory accessible via event_loop_factory(),
   // and then calls Register.
   void Register();
@@ -121,6 +133,14 @@
   realtime_clock::time_point realtime_start_time(
       const Node *node = nullptr) const;
 
+  // Sets the start and end times to replay data until for all nodes.  This
+  // overrides the --start_time and --end_time flags.  The default is to replay
+  // all data.
+  void SetStartTime(std::string start_time);
+  void SetStartTime(realtime_clock::time_point start_time);
+  void SetEndTime(std::string end_time);
+  void SetEndTime(realtime_clock::time_point end_time);
+
   // Causes the logger to publish the provided channel on a different name so
   // that replayed applications can publish on the proper channel name without
   // interference. This operates on raw channel names, without any node or
@@ -277,7 +297,7 @@
     TimestampedMessage PopOldest();
 
     // Returns the monotonic time of the oldest message.
-    BootTimestamp OldestMessageTime() const;
+    BootTimestamp OldestMessageTime();
 
     size_t boot_count() const {
       // If we are replaying directly into an event loop, we can't reboot.  So
@@ -296,7 +316,7 @@
       if (start_time == monotonic_clock::min_time) {
         LOG(ERROR)
             << "No start time, skipping, please figure out when this happens";
-        RunOnStart();
+        NotifyLogfileStart();
         return;
       }
       CHECK_GE(start_time, event_loop_->monotonic_now());
@@ -329,7 +349,9 @@
 
     // Sets the node event loop factory for replaying into a
     // SimulatedEventLoopFactory.  Returns the EventLoop to use.
-    void SetNodeEventLoopFactory(NodeEventLoopFactory *node_event_loop_factory);
+    void SetNodeEventLoopFactory(
+        NodeEventLoopFactory *node_event_loop_factory,
+        SimulatedEventLoopFactory *event_loop_factory);
 
     // Sets and gets the event loop to use.
     void set_event_loop(EventLoop *event_loop) { event_loop_ = event_loop; }
@@ -419,6 +441,18 @@
     void RunOnStart();
     void RunOnEnd();
 
+    // Handles a logfile start event to potentially call the OnStart callbacks.
+    void NotifyLogfileStart();
+    // Handles a start time flag start event to potentially call the OnStart
+    // callbacks.
+    void NotifyFlagStart();
+
+    // Handles a logfile end event to potentially call the OnEnd callbacks.
+    void NotifyLogfileEnd();
+    // Handles a end time flag start event to potentially call the OnEnd
+    // callbacks.
+    void NotifyFlagEnd();
+
     // Unregisters everything so we can destory the event loop.
     // TODO(austin): Is this needed?  OnShutdown should be able to serve this
     // need.
@@ -437,6 +471,18 @@
       }
     }
 
+    // Creates and registers the --start_time and --end_time event callbacks.
+    void SetStartTimeFlag(realtime_clock::time_point start_time);
+    void SetEndTimeFlag(realtime_clock::time_point end_time);
+
+    // Notices the next message to update the start/end time callbacks.
+    void ObserveNextMessage(monotonic_clock::time_point monotonic_event,
+                            realtime_clock::time_point realtime_event);
+
+    // Clears the start and end time flag handlers so we can delete the event
+    // loop.
+    void ClearTimeFlags();
+
     // Sets the next wakeup time on the replay callback.
     void Setup(monotonic_clock::time_point next_time) {
       timer_handler_->Setup(next_time);
@@ -516,6 +562,8 @@
 
     // Factory (if we are in sim) that this loop was created on.
     NodeEventLoopFactory *node_event_loop_factory_ = nullptr;
+    SimulatedEventLoopFactory *event_loop_factory_ = nullptr;
+
     std::unique_ptr<EventLoop> event_loop_unique_ptr_;
     // Event loop.
     const Node *node_ = nullptr;
@@ -524,6 +572,9 @@
     TimerHandler *timer_handler_ = nullptr;
     TimerHandler *startup_timer_ = nullptr;
 
+    std::unique_ptr<EventNotifier> start_event_notifier_;
+    std::unique_ptr<EventNotifier> end_event_notifier_;
+
     // Filters (or nullptr if it isn't a forwarded channel) for each channel.
     // This corresponds to the object which is shared among all the channels
     // going between 2 nodes.  The second element in the tuple indicates if this
@@ -598,6 +649,9 @@
 
   // Whether to exit the SimulatedEventLoop when we finish reading the logs.
   bool exit_on_finish_ = true;
+
+  realtime_clock::time_point start_time_ = realtime_clock::min_time;
+  realtime_clock::time_point end_time_ = realtime_clock::max_time;
 };
 
 }  // namespace logger
diff --git a/aos/events/logging/logger_test.cc b/aos/events/logging/logger_test.cc
index 1732549..3b0b672 100644
--- a/aos/events/logging/logger_test.cc
+++ b/aos/events/logging/logger_test.cc
@@ -523,7 +523,12 @@
   }
 };
 
-void ConfirmReadable(const std::vector<std::string> &files) {
+std::vector<std::pair<std::vector<realtime_clock::time_point>,
+                      std::vector<realtime_clock::time_point>>>
+ConfirmReadable(
+    const std::vector<std::string> &files,
+    realtime_clock::time_point start_time = realtime_clock::min_time,
+    realtime_clock::time_point end_time = realtime_clock::max_time) {
   {
     LogReader reader(SortParts(files));
 
@@ -535,22 +540,65 @@
     reader.Deregister();
   }
   {
+    std::vector<std::pair<std::vector<realtime_clock::time_point>,
+                          std::vector<realtime_clock::time_point>>>
+        result;
     LogReader reader(SortParts(files));
 
+    reader.SetStartTime(start_time);
+    reader.SetEndTime(end_time);
+
     SimulatedEventLoopFactory log_reader_factory(reader.configuration());
     reader.RegisterWithoutStarting(&log_reader_factory);
+    result.resize(
+        configuration::NodesCount(log_reader_factory.configuration()));
     if (configuration::MultiNode(log_reader_factory.configuration())) {
+      size_t i = 0;
       for (const aos::Node *node :
            *log_reader_factory.configuration()->nodes()) {
-        reader.OnStart(node, [node]() {
+        LOG(INFO) << "Registering start";
+        reader.OnStart(node, [node, &log_reader_factory, &result,
+                              node_index = i]() {
           LOG(INFO) << "Starting " << node->name()->string_view();
+          result[node_index].first.push_back(
+              log_reader_factory.GetNodeEventLoopFactory(node)->realtime_now());
         });
+        reader.OnEnd(node, [node, &log_reader_factory, &result,
+                            node_index = i]() {
+          LOG(INFO) << "Ending " << node->name()->string_view();
+          result[node_index].second.push_back(
+              log_reader_factory.GetNodeEventLoopFactory(node)->realtime_now());
+        });
+        ++i;
       }
+    } else {
+      reader.OnStart([&log_reader_factory, &result]() {
+        LOG(INFO) << "Starting";
+        result[0].first.push_back(
+            log_reader_factory.GetNodeEventLoopFactory(nullptr)
+                ->realtime_now());
+      });
+      reader.OnEnd([&log_reader_factory, &result]() {
+        LOG(INFO) << "Ending";
+        result[0].second.push_back(
+            log_reader_factory.GetNodeEventLoopFactory(nullptr)
+                ->realtime_now());
+      });
     }
 
     log_reader_factory.Run();
 
     reader.Deregister();
+
+    for (auto x : result) {
+      for (auto y : x.first) {
+        VLOG(1) << "Start " << y;
+      }
+      for (auto y : x.second) {
+        VLOG(1) << "End " << y;
+      }
+    }
+    return result;
   }
 }
 
@@ -3589,7 +3637,27 @@
   // Confirm that we can parse the result.  LogReader has enough internal CHECKs
   // to confirm the right thing happened.
   const std::vector<LogFile> sorted_parts = SortParts(filenames);
-  ConfirmReadable(filenames);
+  auto result = ConfirmReadable(filenames);
+  EXPECT_THAT(result[0].first, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                      chrono::seconds(1)));
+  EXPECT_THAT(result[0].second,
+              ::testing::ElementsAre(realtime_clock::epoch() +
+                                     chrono::microseconds(34990350)));
+
+  EXPECT_THAT(result[1].first,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch() + chrono::seconds(1),
+                  realtime_clock::epoch() + chrono::microseconds(3323000)));
+  EXPECT_THAT(result[1].second,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch() + chrono::microseconds(13990200),
+                  realtime_clock::epoch() + chrono::microseconds(16313200)));
+
+  EXPECT_THAT(result[2].first, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                      chrono::seconds(1)));
+  EXPECT_THAT(result[2].second,
+              ::testing::ElementsAre(realtime_clock::epoch() +
+                                     chrono::microseconds(34900150)));
 }
 
 // Tests that local data before remote data after reboot is properly replayed.
@@ -3730,9 +3798,201 @@
   // Confirm that we can parse the result.  LogReader has enough internal CHECKs
   // to confirm the right thing happened.
   const std::vector<LogFile> sorted_parts = SortParts(filenames);
-  ConfirmReadable(filenames);
+  auto result = ConfirmReadable(filenames);
+
+  EXPECT_THAT(result[0].first, ::testing::ElementsAre(realtime_clock::epoch()));
+  EXPECT_THAT(result[0].second,
+              ::testing::ElementsAre(realtime_clock::epoch() +
+                                     chrono::microseconds(11000350)));
+
+  EXPECT_THAT(result[1].first,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch(),
+                  realtime_clock::epoch() + chrono::microseconds(107005000)));
+  EXPECT_THAT(result[1].second,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch() + chrono::microseconds(4000150),
+                  realtime_clock::epoch() + chrono::microseconds(111000200)));
+
+  EXPECT_THAT(result[2].first, ::testing::ElementsAre(realtime_clock::epoch()));
+  EXPECT_THAT(result[2].second,
+              ::testing::ElementsAre(realtime_clock::epoch() +
+                                     chrono::microseconds(11000150)));
+
+  auto start_stop_result = ConfirmReadable(
+      filenames, realtime_clock::epoch() + chrono::milliseconds(2000),
+      realtime_clock::epoch() + chrono::milliseconds(3000));
+
+  EXPECT_THAT(start_stop_result[0].first, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                      chrono::seconds(2)));
+  EXPECT_THAT(start_stop_result[0].second, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                       chrono::seconds(3)));
+  EXPECT_THAT(start_stop_result[1].first, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                      chrono::seconds(2)));
+  EXPECT_THAT(start_stop_result[1].second, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                       chrono::seconds(3)));
+  EXPECT_THAT(start_stop_result[2].first, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                      chrono::seconds(2)));
+  EXPECT_THAT(start_stop_result[2].second, ::testing::ElementsAre(realtime_clock::epoch() +
+                                                       chrono::seconds(3)));
 }
 
+// Tests that setting the start and stop flags across a reboot works as
+// expected.
+TEST(MultinodeRebootLoggerTest, RebootStartStopTimes) {
+  aos::FlatbufferDetachedBuffer<aos::Configuration> config =
+      aos::configuration::ReadConfig(ArtifactPath(
+          "aos/events/logging/multinode_pingpong_split3_config.json"));
+  message_bridge::TestingTimeConverter time_converter(
+      configuration::NodesCount(&config.message()));
+  SimulatedEventLoopFactory event_loop_factory(&config.message());
+  event_loop_factory.SetTimeConverter(&time_converter);
+  NodeEventLoopFactory *const pi1 =
+      event_loop_factory.GetNodeEventLoopFactory("pi1");
+  const size_t pi1_index = configuration::GetNodeIndex(
+      event_loop_factory.configuration(), pi1->node());
+  NodeEventLoopFactory *const pi2 =
+      event_loop_factory.GetNodeEventLoopFactory("pi2");
+  const size_t pi2_index = configuration::GetNodeIndex(
+      event_loop_factory.configuration(), pi2->node());
+  NodeEventLoopFactory *const pi3 =
+      event_loop_factory.GetNodeEventLoopFactory("pi3");
+  const size_t pi3_index = configuration::GetNodeIndex(
+      event_loop_factory.configuration(), pi3->node());
+
+  const std::string kLogfile1_1 =
+      aos::testing::TestTmpDir() + "/multi_logfile1/";
+  const std::string kLogfile2_1 =
+      aos::testing::TestTmpDir() + "/multi_logfile2.1/";
+  const std::string kLogfile2_2 =
+      aos::testing::TestTmpDir() + "/multi_logfile2.2/";
+  const std::string kLogfile3_1 =
+      aos::testing::TestTmpDir() + "/multi_logfile3/";
+  util::UnlinkRecursive(kLogfile1_1);
+  util::UnlinkRecursive(kLogfile2_1);
+  util::UnlinkRecursive(kLogfile2_2);
+  util::UnlinkRecursive(kLogfile3_1);
+  {
+    CHECK_EQ(pi1_index, 0u);
+    CHECK_EQ(pi2_index, 1u);
+    CHECK_EQ(pi3_index, 2u);
+
+    time_converter.AddNextTimestamp(
+        distributed_clock::epoch(),
+        {BootTimestamp::epoch(), BootTimestamp::epoch(),
+         BootTimestamp::epoch()});
+    const chrono::nanoseconds reboot_time = chrono::milliseconds(5000);
+    time_converter.AddNextTimestamp(
+        distributed_clock::epoch() + reboot_time,
+        {BootTimestamp::epoch() + reboot_time,
+         BootTimestamp{.boot = 1,
+                       .time = monotonic_clock::epoch() + reboot_time},
+         BootTimestamp::epoch() + reboot_time});
+  }
+
+  std::vector<std::string> filenames;
+  {
+    LoggerState pi1_logger = LoggerState::MakeLogger(
+        pi1, &event_loop_factory, SupportedCompressionAlgorithms()[0]);
+    LoggerState pi3_logger = LoggerState::MakeLogger(
+        pi3, &event_loop_factory, SupportedCompressionAlgorithms()[0]);
+    {
+      // And now start the logger.
+      LoggerState pi2_logger = LoggerState::MakeLogger(
+          pi2, &event_loop_factory, SupportedCompressionAlgorithms()[0]);
+
+      pi1_logger.StartLogger(kLogfile1_1);
+      pi3_logger.StartLogger(kLogfile3_1);
+      pi2_logger.StartLogger(kLogfile2_1);
+
+      event_loop_factory.RunFor(chrono::milliseconds(1005));
+
+      // Now that we've got a start time in the past, turn on data.
+      std::unique_ptr<aos::EventLoop> ping_event_loop =
+          pi1->MakeEventLoop("ping");
+      Ping ping(ping_event_loop.get());
+
+      pi2->AlwaysStart<Pong>("pong");
+
+      event_loop_factory.RunFor(chrono::milliseconds(3000));
+
+      pi2_logger.AppendAllFilenames(&filenames);
+    }
+    event_loop_factory.RunFor(chrono::milliseconds(995));
+    // pi2 now reboots at 5 seconds.
+    {
+      event_loop_factory.RunFor(chrono::milliseconds(1000));
+
+      // Make local stuff happen before we start logging and connect the remote.
+      pi2->AlwaysStart<Pong>("pong");
+      std::unique_ptr<aos::EventLoop> ping_event_loop =
+          pi1->MakeEventLoop("ping");
+      Ping ping(ping_event_loop.get());
+      event_loop_factory.RunFor(chrono::milliseconds(5));
+
+      // Start logging again on pi2 after it is up.
+      LoggerState pi2_logger = LoggerState::MakeLogger(
+          pi2, &event_loop_factory, SupportedCompressionAlgorithms()[0]);
+      pi2_logger.StartLogger(kLogfile2_2);
+
+      event_loop_factory.RunFor(chrono::milliseconds(5000));
+
+      pi2_logger.AppendAllFilenames(&filenames);
+    }
+
+    pi1_logger.AppendAllFilenames(&filenames);
+    pi3_logger.AppendAllFilenames(&filenames);
+  }
+
+  const std::vector<LogFile> sorted_parts = SortParts(filenames);
+  auto result = ConfirmReadable(filenames);
+
+  EXPECT_THAT(result[0].first, ::testing::ElementsAre(realtime_clock::epoch()));
+  EXPECT_THAT(result[0].second,
+              ::testing::ElementsAre(realtime_clock::epoch() +
+                                     chrono::microseconds(11000350)));
+
+  EXPECT_THAT(result[1].first,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch(),
+                  realtime_clock::epoch() + chrono::microseconds(6005000)));
+  EXPECT_THAT(result[1].second,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch() + chrono::microseconds(4900150),
+                  realtime_clock::epoch() + chrono::microseconds(11000200)));
+
+  EXPECT_THAT(result[2].first, ::testing::ElementsAre(realtime_clock::epoch()));
+  EXPECT_THAT(result[2].second,
+              ::testing::ElementsAre(realtime_clock::epoch() +
+                                     chrono::microseconds(11000150)));
+
+  // Confirm we observed the correct start and stop times.  We should see the
+  // reboot here.
+  auto start_stop_result = ConfirmReadable(
+      filenames, realtime_clock::epoch() + chrono::milliseconds(2000),
+      realtime_clock::epoch() + chrono::milliseconds(8000));
+
+  EXPECT_THAT(
+      start_stop_result[0].first,
+      ::testing::ElementsAre(realtime_clock::epoch() + chrono::seconds(2)));
+  EXPECT_THAT(
+      start_stop_result[0].second,
+      ::testing::ElementsAre(realtime_clock::epoch() + chrono::seconds(8)));
+  EXPECT_THAT(start_stop_result[1].first,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch() + chrono::seconds(2),
+                  realtime_clock::epoch() + chrono::microseconds(6005000)));
+  EXPECT_THAT(start_stop_result[1].second,
+              ::testing::ElementsAre(
+                  realtime_clock::epoch() + chrono::microseconds(4900150),
+                  realtime_clock::epoch() + chrono::seconds(8)));
+  EXPECT_THAT(
+      start_stop_result[2].first,
+      ::testing::ElementsAre(realtime_clock::epoch() + chrono::seconds(2)));
+  EXPECT_THAT(
+      start_stop_result[2].second,
+      ::testing::ElementsAre(realtime_clock::epoch() + chrono::seconds(8)));
+}
 
 }  // namespace testing
 }  // namespace logger
diff --git a/aos/events/simulated_event_loop.cc b/aos/events/simulated_event_loop.cc
index a2428a4..a1ef95d 100644
--- a/aos/events/simulated_event_loop.cc
+++ b/aos/events/simulated_event_loop.cc
@@ -1268,6 +1268,11 @@
       event_loop->SetIsRunning(true);
     }
   });
+  scheduler_.set_stopped([this]() {
+    for (SimulatedEventLoop *event_loop : event_loops_) {
+      event_loop->SetIsRunning(false);
+    }
+  });
   scheduler_.set_on_shutdown([this]() {
     VLOG(1) << scheduler_.distributed_now() << " " << NodeName(this->node())
             << monotonic_now() << " Shutting down node.";
@@ -1339,7 +1344,7 @@
 
 void NodeEventLoopFactory::Shutdown() {
   for (SimulatedEventLoop *event_loop : event_loops_) {
-    event_loop->SetIsRunning(false);
+    CHECK(!event_loop->is_running());
   }
 
   CHECK(started_);
@@ -1367,12 +1372,11 @@
 
 void SimulatedEventLoopFactory::RunFor(monotonic_clock::duration duration) {
   // This sets running to true too.
-  scheduler_scheduler_.RunOnStartup();
   scheduler_scheduler_.RunFor(duration);
   for (std::unique_ptr<NodeEventLoopFactory> &node : node_factories_) {
     if (node) {
       for (SimulatedEventLoop *loop : node->event_loops_) {
-        loop->SetIsRunning(false);
+        CHECK(!loop->is_running());
       }
     }
   }
@@ -1380,12 +1384,11 @@
 
 void SimulatedEventLoopFactory::Run() {
   // This sets running to true too.
-  scheduler_scheduler_.RunOnStartup();
   scheduler_scheduler_.Run();
   for (std::unique_ptr<NodeEventLoopFactory> &node : node_factories_) {
     if (node) {
       for (SimulatedEventLoop *loop : node->event_loops_) {
-        loop->SetIsRunning(false);
+        CHECK(!loop->is_running());
       }
     }
   }
@@ -1458,6 +1461,11 @@
   return std::move(result);
 }
 
+void SimulatedEventLoopFactory::AllowApplicationCreationDuring(
+    std::function<void()> fn) {
+  scheduler_scheduler_.TemporarilyStopAndRun(std::move(fn));
+}
+
 void NodeEventLoopFactory::Disconnect(const Node *other) {
   factory_->bridge_->Disconnect(node_, other);
 }
diff --git a/aos/events/simulated_event_loop.h b/aos/events/simulated_event_loop.h
index bd589d6..9a447e9 100644
--- a/aos/events/simulated_event_loop.h
+++ b/aos/events/simulated_event_loop.h
@@ -128,6 +128,11 @@
   // tests.
   void SkipTimingReport();
 
+  // Re-enables application creation for the duration of fn.  This is mostly to
+  // allow use cases like log reading to create applications after the node
+  // starts up without stopping execution.
+  void AllowApplicationCreationDuring(std::function<void()> fn);
+
  private:
   friend class NodeEventLoopFactory;
 
diff --git a/aos/events/simulated_event_loop_test.cc b/aos/events/simulated_event_loop_test.cc
index a94b895..09202ff 100644
--- a/aos/events/simulated_event_loop_test.cc
+++ b/aos/events/simulated_event_loop_test.cc
@@ -181,6 +181,29 @@
   EXPECT_EQ(counter, 0);
 }
 
+// Test that TemporarilyStopAndRun respects and preserves running.
+TEST(EventSchedulerTest, TemporarilyStopAndRun) {
+  int counter = 0;
+  EventSchedulerScheduler scheduler_scheduler;
+  EventScheduler scheduler(0);
+  scheduler_scheduler.AddEventScheduler(&scheduler);
+
+  scheduler_scheduler.TemporarilyStopAndRun(
+      [&]() { CHECK(!scheduler_scheduler.is_running()); });
+  ASSERT_FALSE(scheduler_scheduler.is_running());
+
+  FunctionEvent e([&]() {
+    counter += 1;
+    CHECK(scheduler_scheduler.is_running());
+    scheduler_scheduler.TemporarilyStopAndRun(
+        [&]() { CHECK(!scheduler_scheduler.is_running()); });
+    CHECK(scheduler_scheduler.is_running());
+  });
+  scheduler.Schedule(monotonic_clock::epoch() + chrono::seconds(1), &e);
+  scheduler_scheduler.Run();
+  EXPECT_EQ(counter, 1);
+}
+
 void SendTestMessage(aos::Sender<TestMessage> *sender, int value) {
   aos::Sender<TestMessage>::Builder builder = sender->MakeBuilder();
   TestMessage::Builder test_message_builder =
diff --git a/frc971/imu/ADIS16505.cc b/frc971/imu/ADIS16505.cc
index 4c31cab..bd65e4d 100644
--- a/frc971/imu/ADIS16505.cc
+++ b/frc971/imu/ADIS16505.cc
@@ -377,7 +377,12 @@
     pwm_set_gpio_level(RATE_PWM, rate_level);
 
     // 0 to 360
-    uint16_t heading_level = (int16_t)(fmod(yaw, 360) / 360.0 * PWM_TOP);
+    double wrapped_heading = fmod(yaw, 360);
+    if (wrapped_heading < 0) {
+      wrapped_heading = wrapped_heading + 360;
+    }
+
+    uint16_t heading_level = (int16_t)(wrapped_heading / 360.0 * PWM_TOP);
     pwm_set_gpio_level(HEADING_PWM, heading_level);
   }
 
diff --git a/frc971/raspi/rootfs/README.md b/frc971/raspi/rootfs/README.md
index a9c7251..f8d9971 100644
--- a/frc971/raspi/rootfs/README.md
+++ b/frc971/raspi/rootfs/README.md
@@ -1,3 +1,5 @@
+# Creating an SD card to run the Raspberry Pis
+
 This modifies a stock debian root filesystem to be able to operate as a vision
 pi.  It is not trying to be reproducible, but should be good enough for FRC
 purposes.
@@ -5,15 +7,37 @@
 The default hostname and IP is pi-971-1, 10.9.71.101.
   Username pi, password raspberry.
 
-Download 2021-10-30-raspios-bullseye-armhf-lite.img (or any newer
-bullseye version, as a .zip file) from
-`https://www.raspberrypi.org/downloads/raspberry-pi-os/`, extract
-(unzip) the .img file, and edit `modify_rootfs.sh` to point to it.
+## Build the real-time kernel using `build_kernel.sh`
 
-Run modify_rootfs.sh to build the filesystem (you might need to hit
+- Checkout the real-time kernel source code, e.g.,
+  `cd CODE_DIR`
+  `git clone git@github.com:frc971/linux.git`
+  `git checkout frc971-5.10-pi4-rt branch`
+
+- Run `build_kernel.sh` to compile the real-time kernel
+  `cd ROOTFS_DIR` (where ROOTFS_DIR -> //frc971/raspi/rootfs)
+  `./build_kernel.sh CODE_DIR/linux kernel_5.10.tar.gz`
+
+## Download the Raspberry Pi OS
+
+Download the appropriate Raspberry Pi OS image, e.g.,
+`2022-01-28-raspios-bullseye-arm64-lite.img` (or any newer arm64
+bullseye version, as a .zip file) from
+`https://www.raspberrypi.org/downloads/raspberry-pi-os/`, and extract
+(unzip) the .img file.
+
+## Create our custom OS image using `modify_root.sh`
+
+- Edit `modify_rootfs.sh` to point to the kernel file (e.g.,
+`KERNEL=kernel_5.10.tar.gz`) and the Raspberry Pi OS image (e.g.,
+`IMAGE=2022-01-28-raspios-bullseye-arm64-lite.img`)
+
+- Run modify_rootfs.sh to build the filesystem (you might need to hit
 return in a spot or two and will need sudo privileges to mount the
 partition):
-  * `modify_root.sh`
+  * `./modify_root.sh`
+
+## Write the file system to the SD card
 
 VERY IMPORTANT NOTE: Before doing the next step, use `lsblk` to find
 the device and make absolutely sure this isn't your hard drive or
diff --git a/frc971/raspi/rootfs/make_sd.sh b/frc971/raspi/rootfs/make_sd.sh
index 5f1a0e1..3bafacc 100755
--- a/frc971/raspi/rootfs/make_sd.sh
+++ b/frc971/raspi/rootfs/make_sd.sh
@@ -32,15 +32,15 @@
   target /root/bin/change_hostname.sh "${1}"
 fi
 
-echo "Starting a shell for any manual configuration"
-target /bin/bash --rcfile /root/.bashrc
-
 # Put a timestamp on when this card got created and by whom
 TIMESTAMP_FILE="${PARTITION}/home/pi/.DiskFlashedDate.txt"
 date > "${TIMESTAMP_FILE}"
 git rev-parse HEAD >> "${TIMESTAMP_FILE}"
 whoami >> "${TIMESTAMP_FILE}"
 
+echo "Starting a shell for any manual configuration"
+target /bin/bash --rcfile /root/.bashrc
+
 # Found I had to do a lazy force unmount ("-l" flag) to make it work reliably
 sudo umount -l "${PARTITION}"
 rmdir "${PARTITION}"
diff --git a/frc971/wpilib/imu.fbs b/frc971/wpilib/imu.fbs
index 33bad72..565e3a4 100644
--- a/frc971/wpilib/imu.fbs
+++ b/frc971/wpilib/imu.fbs
@@ -105,10 +105,10 @@
   // from the Raspberry Pi Pico to the Raspberry Pi.
   checksum_failed:bool (id:22);
 
-  // The position of the left drivetrain encoder in encoder ticks
-  left_encoder:int (id: 17);
-  // The position of the right drivetrain encoder in encoder ticks
-  right_encoder:int (id: 18);
+  // The position of the left drivetrain encoder in meters
+  left_encoder:double (id: 17);
+  // The position of the right drivetrain encoder in meters
+  right_encoder:double (id: 18);
 
   // For an ADIS16470, the DIAG_STAT value immediately after reset.
   start_diag_stat:ADIS16470DiagStat (id: 13);
diff --git a/y2020/vision/calibration.cc b/y2020/vision/calibration.cc
index 0b05d10..ec5bf40 100644
--- a/y2020/vision/calibration.cc
+++ b/y2020/vision/calibration.cc
@@ -28,8 +28,8 @@
       : event_loop_(event_loop),
         pi_(pi),
         pi_number_(aos::network::ParsePiNumber(pi)),
-        prev_rvec_(Eigen::Vector3d::Zero()),
-        prev_tvec_(Eigen::Vector3d::Zero()),
+        H_camera_board_(Eigen::Affine3d()),
+        prev_H_camera_board_(Eigen::Affine3d()),
         charuco_extractor_(
             event_loop, pi,
             [this](cv::Mat rgb_image,
@@ -67,16 +67,15 @@
     // Calibration calculates rotation and translation delta from last image
     // captured to automatically capture next image
 
-    Eigen::Matrix3d r_aff =
-        Eigen::AngleAxisd(rvec_eigen.norm(), rvec_eigen / rvec_eigen.norm())
-            .toRotationMatrix();
-    Eigen::Matrix3d prev_r_aff =
-        Eigen::AngleAxisd(prev_rvec_.norm(), prev_rvec_ / prev_rvec_.norm())
-            .toRotationMatrix();
+    Eigen::Affine3d H_board_camera =
+        Eigen::Translation3d(tvec_eigen) *
+        Eigen::AngleAxisd(rvec_eigen.norm(), rvec_eigen / rvec_eigen.norm());
+    H_camera_board_ = H_board_camera.inverse();
+    Eigen::Affine3d H_delta = H_board_camera * prev_H_camera_board_;
 
-    Eigen::AngleAxisd delta_r = Eigen::AngleAxisd(r_aff * prev_r_aff.inverse());
+    Eigen::AngleAxisd delta_r = Eigen::AngleAxisd(H_delta.rotation());
 
-    Eigen::Vector3d delta_t = tvec_eigen - prev_tvec_;
+    Eigen::Vector3d delta_t = H_delta.translation();
 
     double r_norm = std::abs(delta_r.angle());
     double t_norm = delta_t.norm();
@@ -84,8 +83,7 @@
     int keystroke = cv::waitKey(1);
     if (r_norm > kDeltaRThreshold || t_norm > kDeltaTThreshold) {
       if (valid) {
-        prev_rvec_ = rvec_eigen;
-        prev_tvec_ = tvec_eigen;
+        prev_H_camera_board_ = H_camera_board_;
 
         all_charuco_ids_.emplace_back(std::move(charuco_ids));
         all_charuco_corners_.emplace_back(std::move(charuco_corners));
@@ -194,8 +192,8 @@
   std::vector<std::vector<int>> all_charuco_ids_;
   std::vector<std::vector<cv::Point2f>> all_charuco_corners_;
 
-  Eigen::Vector3d prev_rvec_;
-  Eigen::Vector3d prev_tvec_;
+  Eigen::Affine3d H_camera_board_;
+  Eigen::Affine3d prev_H_camera_board_;
 
   CharucoExtractor charuco_extractor_;
 };
diff --git a/y2022/constants.h b/y2022/constants.h
index 050c5c7..92f3a48 100644
--- a/y2022/constants.h
+++ b/y2022/constants.h
@@ -30,6 +30,15 @@
            constants::Values::kDrivetrainEncoderRatio() *
            kDrivetrainEncoderCountsPerRevolution();
   }
+
+  static double DrivetrainEncoderToMeters(int32_t in) {
+    return ((static_cast<double>(in) /
+             kDrivetrainEncoderCountsPerRevolution()) *
+            (2.0 * M_PI)) *
+           kDrivetrainEncoderRatio() *
+           control_loops::drivetrain::kWheelRadius;
+  }
+
   static constexpr double kRollerSupplyCurrentLimit() { return 30.0; }
   static constexpr double kRollerStatorCurrentLimit() { return 40.0; }
 
diff --git a/y2022/control_loops/python/BUILD b/y2022/control_loops/python/BUILD
index bc2b624..4049acc 100644
--- a/y2022/control_loops/python/BUILD
+++ b/y2022/control_loops/python/BUILD
@@ -64,6 +64,22 @@
     ],
 )
 
+py_binary(
+    name = "turret",
+    srcs = [
+        "turret.py",
+    ],
+    legacy_create_init = False,
+    target_compatible_with = ["@platforms//cpu:x86_64"],
+    deps = [
+        ":python_init",
+        "//external:python-gflags",
+        "//external:python-glog",
+        "//frc971/control_loops/python:angular_system",
+        "//frc971/control_loops/python:controls",
+    ],
+)
+
 py_library(
     name = "python_init",
     srcs = ["__init__.py"],
diff --git a/y2022/control_loops/python/turret.py b/y2022/control_loops/python/turret.py
new file mode 100644
index 0000000..83ba4b3
--- /dev/null
+++ b/y2022/control_loops/python/turret.py
@@ -0,0 +1,54 @@
+#!/usr/bin/python3
+
+from aos.util.trapezoid_profile import TrapezoidProfile
+from frc971.control_loops.python import control_loop
+from frc971.control_loops.python import angular_system
+from frc971.control_loops.python import controls
+import numpy
+import sys
+from matplotlib import pylab
+import gflags
+import glog
+
+FLAGS = gflags.FLAGS
+
+try:
+    gflags.DEFINE_bool('plot', False, 'If true, plot the loop response.')
+except gflags.DuplicateFlagError:
+    pass
+
+kTurret = angular_system.AngularSystemParams(
+    name='Turret',
+    motor=control_loop.Falcon(),
+    G=0.01,
+    J=2.0,
+    q_pos=0.40,
+    q_vel=20.0,
+    kalman_q_pos=0.12,
+    kalman_q_vel=2.0,
+    kalman_q_voltage=4.0,
+    kalman_r_position=0.05,
+    radius=24 * 0.0254)
+
+
+def main(argv):
+    if FLAGS.plot:
+        R = numpy.matrix([[numpy.pi], [0.0]])
+        angular_system.PlotKick(kTurret, R)
+        angular_system.PlotMotion(kTurret, R)
+
+    # Write the generated constants out to a file.
+    if len(argv) != 5:
+        glog.fatal(
+            'Expected .h file name and .cc file name for the turret and integral turret.'
+        )
+    else:
+        namespaces = ['y2022', 'control_loops', 'superstructure', 'turret']
+        angular_system.WriteAngularSystem(kTurret, argv[1:3], argv[3:5],
+                                          namespaces)
+
+
+if __name__ == '__main__':
+    argv = FLAGS(sys.argv)
+    glog.init()
+    sys.exit(main(argv))
diff --git a/y2022/localizer/imu.cc b/y2022/localizer/imu.cc
index dbdc1a1..db7ec8f 100644
--- a/y2022/localizer/imu.cc
+++ b/y2022/localizer/imu.cc
@@ -2,6 +2,7 @@
 
 #include "aos/util/crc32.h"
 #include "glog/logging.h"
+#include "y2022/constants.h"
 
 namespace y2022::localizer {
 
@@ -120,8 +121,10 @@
 
     // extra data from the pico
     imu_builder.add_pico_timestamp_us(pico_timestamp);
-    imu_builder.add_left_encoder(encoder1_count);
-    imu_builder.add_right_encoder(encoder2_count);
+    imu_builder.add_left_encoder(
+        constants::Values::DrivetrainEncoderToMeters(encoder1_count));
+    imu_builder.add_right_encoder(
+        constants::Values::DrivetrainEncoderToMeters(encoder2_count));
     imu_builder.add_previous_reading_diag_stat(diag_stat_offset);
   }
 
diff --git a/y2022/vision/blob_detector.cc b/y2022/vision/blob_detector.cc
index 76b16ca..ce257a9 100644
--- a/y2022/vision/blob_detector.cc
+++ b/y2022/vision/blob_detector.cc
@@ -9,15 +9,30 @@
 #include "opencv2/features2d.hpp"
 #include "opencv2/imgproc.hpp"
 
-DEFINE_uint64(green_delta, 50,
-              "Required difference between green pixels vs. red and blue");
+DEFINE_uint64(red_delta, 100,
+              "Required difference between green pixels vs. red");
+DEFINE_uint64(blue_delta, 50,
+              "Required difference between green pixels vs. blue");
+
 DEFINE_bool(use_outdoors, false,
             "If true, change thresholds to handle outdoor illumination");
+DEFINE_uint64(outdoors_red_delta, 100,
+              "Difference between green pixels vs. red, when outdoors");
+DEFINE_uint64(outdoors_blue_delta, 15,
+              "Difference between green pixels vs. blue, when outdoors");
 
 namespace y2022 {
 namespace vision {
 
 cv::Mat BlobDetector::ThresholdImage(cv::Mat bgr_image) {
+  size_t red_delta = FLAGS_red_delta;
+  size_t blue_delta = FLAGS_blue_delta;
+
+  if (FLAGS_use_outdoors) {
+    red_delta = FLAGS_outdoors_red_delta;
+    red_delta = FLAGS_outdoors_blue_delta;
+  }
+
   cv::Mat binarized_image(cv::Size(bgr_image.cols, bgr_image.rows), CV_8UC1);
   for (int row = 0; row < bgr_image.rows; row++) {
     for (int col = 0; col < bgr_image.cols; col++) {
@@ -27,8 +42,7 @@
       uint8_t red = pixel.val[2];
       // Simple filter that looks for green pixels sufficiently brigher than
       // red and blue
-      if ((green > blue + FLAGS_green_delta) &&
-          (green > red + FLAGS_green_delta)) {
+      if ((green > blue + blue_delta) && (green > red + red_delta)) {
         binarized_image.at<uint8_t>(row, col) = 255;
       } else {
         binarized_image.at<uint8_t>(row, col) = 0;
@@ -180,11 +194,11 @@
     // when the camera is the farthest from the target, at the field corner.
     // We can solve for the pitch of the blob:
     // blob_pitch = atan((height_tape - height_camera) / depth) + camera_pitch
-    // The triangle with the height of the tape above the camera and the camera
-    // depth is similar to the one with the focal length in y pixels and the y
-    // coordinate offset from the center of the image.
-    // Therefore y_offset = focal_length_y * tan(blob_pitch), and
-    // y = -(y_offset - offset_y)
+    // The triangle with the height of the tape above the camera and the
+    // camera depth is similar to the one with the focal length in y pixels
+    // and the y coordinate offset from the center of the image. Therefore
+    // y_offset = focal_length_y * tan(blob_pitch), and y = -(y_offset -
+    // offset_y)
     constexpr int kMaxY = 400;
     constexpr double kTapeAspectRatio = 5.0 / 2.0;
     constexpr double kAspectRatioThreshold = 1.6;
diff --git a/y2022/wpilib_interface.cc b/y2022/wpilib_interface.cc
index 0ee1e92..673fa80 100644
--- a/y2022/wpilib_interface.cc
+++ b/y2022/wpilib_interface.cc
@@ -68,14 +68,6 @@
 // DMA stuff and then removing the * 2.0 in *_translate.
 // The low bit is direction.
 
-double drivetrain_translate(int32_t in) {
-  return ((static_cast<double>(in) /
-           Values::kDrivetrainEncoderCountsPerRevolution()) *
-          (2.0 * M_PI)) *
-         Values::kDrivetrainEncoderRatio() *
-         control_loops::drivetrain::kWheelRadius;
-}
-
 double drivetrain_velocity_translate(double in) {
   return (((1.0 / in) / Values::kDrivetrainCyclesPerRevolution()) *
           (2.0 * M_PI)) *
@@ -127,12 +119,14 @@
       frc971::control_loops::drivetrain::Position::Builder drivetrain_builder =
           builder.MakeBuilder<frc971::control_loops::drivetrain::Position>();
       drivetrain_builder.add_left_encoder(
-          drivetrain_translate(drivetrain_left_encoder_->GetRaw()));
+          constants::Values::DrivetrainEncoderToMeters(
+              drivetrain_left_encoder_->GetRaw()));
       drivetrain_builder.add_left_speed(
           drivetrain_velocity_translate(drivetrain_left_encoder_->GetPeriod()));
 
       drivetrain_builder.add_right_encoder(
-          -drivetrain_translate(drivetrain_right_encoder_->GetRaw()));
+          -constants::Values::DrivetrainEncoderToMeters(
+              drivetrain_right_encoder_->GetRaw()));
       drivetrain_builder.add_right_speed(-drivetrain_velocity_translate(
           drivetrain_right_encoder_->GetPeriod()));