文档介绍：Things ? Should be working on your project at this point – Your group should have something to work on as of today. – Your group should target having ponents be “ mostly working ” by the milestone meeting (April 8 th)? We ’ re nearing the end of regular lectures. – More time for project work. 2 What ’ s left 3 Outline ?Q uick review of real-time systems ? Overview of RTOSes – Goals of an RTOS – Features you might want in an RTOS ? Learning by example: FreeRTOS – Introduction – Tasks – Interrupts – Internals (briefly) – What ’ s missing? 4 Outline ?Q uick overview of real-time systems ? Overview of RTOSes – Goals of an RTOS – Features you might want in an RTOS ? Learning by example: FreeRTOS – Introduction – Tasks – Interrupts – Internals (briefly) – What ’ s missing? 5 What is a Real-Time System? ? Real-time systems have been defined as: "those systems in which the correctness of the system depends not only on the logical result of putation, but also on the time at which the results are produced"; – J. Stankovic , "Misconceptions About Real-Time Computing," puter, 21(10), October 1988. RTS overview 2017-1-14 6 Real-Time Characteristics ? Pretty much your typical embedded system – Sensors & actuators all controlled by a processor. – The big difference is timing constraints (deadlines). ? Those tasks can be broken into two categories 1 – Periodic Tasks : Time-driven and recurring at regular intervals. ? A car checking for a wall every seconds; ? An air monitoring system grabbing an air sample every 10 seconds. – Aperiodic : event-driven ? That car having to react to a wall it found ? The loss work connectivity. 1 Sporadic tasks are sometimes also discussed as a third category. They are tasks similar to aperiodic tasks but activated with some known bounded rate. The bounded rate is characterized by a minimum interval of time between two essive activations. RTS overview 2017-1-14 7 Some Definitions ? Timing constraint: constraint impose