Chapter 11. Using Interrupts For Timing

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IN THIS CHAPTER

• Linux Timing Sources

• Measuring Interrupt Latency

• Implementing the Race Timer

• Additional Reading

The first snowfall at Silverjack filled the air with excitement. Soon the village would bustle and the slopes would open. As in past years, many skiers and snowboarders would race against the clock on the mountain's racecourse. This year, however, Project Trailblazer wants to collect, display, log, and post race results. Using embedded Linux for Silverjack race timing will reduce data entry errors, increase efficiency, and enhance the racers' experience.

This chapter explores using Linux as an event timer with 1-millisecond resolution. The Project Trailblazer engineers need to develop interrupt handlers for the target boards the MZ104, the MediaEngine, and the RPX-CLLF. Then they need to use these handlers to measure average interrupt latencies. The engineers need to design a race timer that uses a split interrupt approach with "top half" and "bottom half" handler routines, tasklets, and a self-rescheduling kernel timer.

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