mo3pheus / marsrover Goto Github PK

1. Should not get comsDelay when processing instructionQueue
2. Should have error recovery in case of exceptions while processingInstructionQueue.

Fix Radio - if positionSensor.comsDelay throws an Exception use last known comsDelay

1. SleepBreather's rover instance is not volatile.
2. There is no hard interrupt to the sleepBreather upon rover wakeUp().

Result is that sleepingAnimation is shown even if the batteryMonitor has put the rover into sleeping state.

Problem: The SpacecraftClock and PositionSensor for the Rover can get out of sync ( a minute apart or more ).

Cause: The SpacecraftClock and PositionSensors run on separate threads and get kicked off at different times, Over a period of time due to thread synchronization and waits for lock acquisition, they can get out of sync. If the timeScaleFactor is 60 - these discrepancies can add up quickly.

Solution: There is a command you can issue to the Rover for clockSynchronization - this syncs up the spaceCraftClock and the positionSensor. Unfortunately right now the rover waits for this command to be explicitly issued from the commandCenter.

Ideally the rover would have a tune up thread that measures the difference between the spaceCraftClock and the positionSensor Clock and triggers a sync if that difference gets above a certain threshold.

Solution II - tried implementing this but it failed due to thread sync issues. But ideally you could have the PositionSensor as an observer to the spaceCraftClock - i.e. when the spaceCraftClock updates, so does the positionSensor. This makes a cleaner solution than having the positionSensor ticking on a separate thread and dependent upon periodic forced syncs. The clock Syncs are not without their cost - the pacemaker and roverGarbageCollector are both restarted when this happens. Also conceptually the spaceCraftClock should be the final word upon what time it is on the spaceCraft. This is the computer's internal clock and all components rely upon it for their time. Look to how the TelemetrySensor is tied to the trackingAnimationEngine to see how this could be done.

Things to learn from this issue:

1. Thread synchronization.
2. Usage of the marsConfig properties file in configuring the rover.
3. Understanding of the timeScale factor that affects all rover communications.
4. If SolutionII is selected, the observer design pattern.