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Problems with USB running off IRC48

Question asked by Ove-Anders Gaarder Aune on Dec 4, 2015
Latest reply on Dec 9, 2015 by Ove-Anders Gaarder Aune

Having some issues with getting the USB to work on a MK22FN512VLL12 using the IRC48 oscillator. ( Using Freescale USB Stack 4.1.1 )


I have enabled the oscillator in USB_RECOVER_INT_EN, also selected it as USB source in SIM ( USBSRC=1 and FLLPLLSEL =3). I also also measured the IRC48CLK on PTC3 when selecting CLKOUT = 7. so the clock seems to be running.


I can measure that the DP+ not gets pulled high once the register is set ( NONOTGPULLUP ), so guessing that this means that the USB module is still static, but can't understand why.


PLL and FLL are off, cpu is runnig of fast IRC ( 4MHz ). Normally operating in VLPR mode, but once USB cable is connected, I go back into RUN mode. Keeping LP bit set to disable PLL and FLL as they are not used.