Tony Abbey

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9 years, 10 months ago.

Low power modes for Nucleo L053R8

I went to an ST micro workshop today and learnt about all the low power modes available for this processor - resulting in supply currents down to sub microamp. Apart from changing the clock speed and setting the processor into a sleep mode, does the mbed system support any other low power modes - eg turning off the pll clock gen, reducing the core voltage, setting internal regulators into low power mode, turning off unused features etc. Is their a command to control the required function registers?

1 Answer

Martin Kojtal
9 years, 10 months ago.

Hello,

there isn't available any low power manager in the mbed. There are some features considered being low-powered. As: sleep(), deep_sleep() methods. The peripherals should initialize its clock source accroding to systemcoreclock. The problematic part is to disabling peripherals which an application does not want to use prior entering low power. This has to be managed by an application at the moment..

A flow: 1. Desired clock freq, do some work.... 2. Time to go to the sleep, change clocking, disable peripherals clocks, set source of wake up, sleep 3. Wake up, disable low power mode settings (periphreal low power enablement, or any specific registers), enable peripherals and go back to 1.

Most of the code to implement 1-3 needs to be handled by an application, at the moment. What I missed above, a need to reenable peripherals once clocks are changed, to calculate their specific clocking... Hope this brings some light to low power problematic and what should be improved.

Regards,
0xc0170

Thanks Martin Although you say there is no low power manager in mbed, is it still possible to write to the relevant control address registers assuming you fully understand the processor's data sheet, or is this hidden from the user?

posted by Tony Abbey 19 Jun 2014

Yes, that's why I outlined that the flow needs to be mostly implemented in the application. There is ST HAL files (drivers) which you can use, might facilitate your work.

posted by Martin Kojtal 19 Jun 2014