Power optimisation

27 Feb 2010

> At last I would like also to disable the PLL and all
> the additional
> pheripheral such as ethernet device in order to
> decrease the power
> consumption to suit my application. Is it
> possible?
> And how can I do that?

mbed is designed for rapid prototyping, and so the features of the tools and hardware have been chosen to make it as easy as possible to get started. Some optimisations like power management are most often required at the product develoment stage, rather than at the rapid prototyping stage, and so are currently not addressed by mbed.

However, I can confirm that in the standard startup, the Ethernet MAC is off, the Phy is held in reset and its oscillator is switched off. In addition, all peripherals are also powered down.

The MCU on mbed is an NXP LPC1768 and the binary output by our compiler runs on the bare metal, there is no runtime environment. If you wish to manipulate things like the PLLs, it is possible by accessing the LPC1768 registers or better still, going through the CMSIS layer. if your are looking to fully optimise an LPC1768 design for power, you may wish to look at other LPC1768 evaluation boards which do not have the mbed interface onboard, or a custom PCB design with only the rquired hardware.