Energy efficient mixed task handling on real-time embedded systems using FreeRTOS

With the increased use of embedded devices in Industrial electronics, like relays, battery life has gained more and more attention. Modern processors can use Dynamic Voltage Frequency Scaling (DVFS) techniques for energy reduction and temperature control. However, DVFS is not well supported by systems running with Real-Time operating systems like FreeRTOS, which is a widely used real-time operation system (RTOS) in the industry. Furthermore, energy-efficient DVFS techniques for Mixed Tasksets (including periodic and aperiodic tasks) are hardly investigated. This paper extends the classic well-known DVFS technique Cycle Conserving algorithm to handle Mixed Taskset (CCMT algorithm) and implements it on a real-time embedded platform powered by FreeRTOS. We describe our experience implementing CCMT on a real platform with limited DVFS and corresponding scheduler support. Results show that we can successfully apply CCMT to handle aperiodic requests while meeting the deadlines of the periodic tasks and saving energy on the FreeRTOS platform. The algorithm is tested on an ARM Cortex-M7 processor integrated with frequency scaling and power management. Over 5% to 10% energy savings can be achieved for a standard real-time scheduling mechanism without penalty in application throughput.