APS - Akustiskt positioneringssystem
The objective of this work was to evaluate and implement a number of energy saving functions for a specific embedded system. The functions were then grouped into a number of energy levels with known properties in terms of functionality, energy consumption, and transition time between the levels.The embedded system consisted of an AT91 ARM9 processor, GSM/GPRS modem, display, Ethernet and other peripheral units. Some energy saving methods that were considered were suspend to RAM, suspend to disk, frequency scaling, and methods for saving energy in the modem, Ethernet, USB and display backlight. The functions were grouped into levels and an interface was specified for controlling the energy level.It proved possible to get known properties within the defined energy levels, even though the paritioning of functions into these levels proved to be sub-optimal in a typical application usage scenario because it was designed for mainly energy consumption, not usage.The final result is a number of energy saving functions grouped into levels, which are controllable via an application interface. Each of the levels have a known energy consumption in both loaded and un-loaded mode.