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Kinetis Kl24 USB operation in low power modes

Question asked by Szymon Mroczek on Dec 21, 2013
Latest reply on Jul 2, 2014 by Kenan SUN

Hi All,

 

I am using Kinetis MKL24 MCU. I need to operate in low power modes (VLLS) and I also need to have USB communication. I am using Freescale's Processor Expert USB CDC stack. Do you have any ideas how to achieve USB connection detection and enumeration while in VLLS (or LLS) power mode? The LLWU module does not contain USB as a wake up source.

My idea is to set up LPTMR as a periodic wake up source. Each time MCU wakes up due to LPTMR I enable PLL clock, initialise USB CDC component and check if any USB event happens. If there's no connection I switch off PLL clock and go back to sleep. LPTMR period is set up to 2 seconds...

 

Prior to trying that idea I would like to ask if any of you have some ideas to share about it...

Thanks!

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