Designing An ARM-Based Multithreaded Audio/Visual/Motion Recording System: Part 1

By Edward L. Lamie, Express Logic
Oct 16 2006 (0:15 AM), Embedded.com

Although it is a generic case study design - not an actual implementation - a real time video/ audio/ motion (VAM) recording system highlights a number of key operating system features and services that must be considered in any embedded system design, including:

application timers
threads
message queues
mutexes
memory byte pools

Designed for use in motorized vehicle fleets this case study depends heavily on the use of application timers. One reason for using so many timers is because we need to schedule the copying of data from the temporary memory to the protected memory whenever any one of four events occurs.

Our design provides the ability to record several events within each 24-second time frame, rather than just one. Application timers play a major role in providing this feature. We also used application timers to simulate interrupts that signify the occurrence of events, and we used one timer to display periodic system statistics.

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