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Resuming USB Communications after exiting VLPS with PLL

Question asked by Chuck Horkin on Aug 14, 2014
Latest reply on Aug 22, 2014 by Chuck Horkin



I'm using a PLL with an external oscillator to run the USB module on a KL25.  When the USB bus is suspended, I bring the device to VLPS.  When I resume (either from a TSI ISR or the Asyncronous USB wakeup) my understanding is that I have to re-enable the PLL.  I'm doing this and it seems to be working, but every so often I find that I lose communications with the device and have to power cycle.


Does anyone know the exact steps required to reinitialize the PLL, AND, how to handle that in code that has multiple ISR wakeup sources that may preempt eachother?