Posted on March 31, 2016 at 21:57Hi,
We're trying to reduce power consumption when not suspended and using USB. During the time when we are not handing USB interrupts, we would like to run at a slower core clock speed. I'm wondering if this is possible or not?
Looking at CubeMx and the Reference Manual, I see that the AHB clock must be 30MHz or higher for the USB HS PHY. However, I also see that this clock is used to access the USB registers. So, my question is if I can switch the SYSCLK to use the HSI using the System Clock Mux as long as I am not accessing the USB peripheral? This would bring the AHB down to 16MHz. I would then disable interrupts and do a WFI and then use the PLL clock again after I wake.
If I can do this, are there steps I need to take when I switch back to the PLLCLK? For example, do I need to set the HRST bit in the USB PHY?
If I can't do this, is there a suggestion? We don't really want to run at full tilt when we aren't doing anything.
Thanks.
#clocks #usb #power #system
