New-bie question on Low power modes: Sleep/LP Slepp

[martinj3456]

Posted on January 16, 2016 at 18:52

Hi,

I am a beginner and experimenting with low power modes. I'm looking for two answers: 1. Is Sleep mode is mandatory to be configured with HSI, or we can also configure it with HSE 8MHz? SPL example and datasheets use HSI 16MHz in all place for Sleep. To save HSE switch-on (~1ms) time, I am trying a low power mode with HSE. My project needs to switch run/low power mode in every 10ms. 2. In other experiment with LP sleep, do we need to enable PWR_UltraLowPowerCmd() & FLASH_SLEEPPowerDownCmd() every time before going to sleep and disable these two at wake-up routine, or it'll be disabled automatically? Thank you for your answer.

[Tesla DeLorean]

Posted on January 16, 2016 at 19:28

What STM32 part, specifically, are we talking about?

Do you have anything timing critical that needs a crystal based HSE source?The HSI is preferable in that it is fast and starts quickly and predictably. Many boards don't have an HSE, and the DISCO boards often take an 8 MHz clock signal from the ST-LINK rather than actually using the oscillator.