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OMAP3530 - Use McSPI (13MHz) and USB at Same Time

Felipe Souza
Prodigy 195 points

Hi ,

In my application I have to use McSPI at 13 MHz but I would like to use a USB Host interface.

I didn't know much about USB , but I think it uses a clock multiple of 48 MHz. and analyzing OMAP35xx architecture I saw that they share the same line of clock.

I need to use both at the same time. The McSPI will write data with DMA and USB can be requested sometime.

 

Anyone know a solution for this problem ? Or another approach to this problem ?

Thanks.

  • 0
    TI__Mastermind 41665 points

    From what I can tell in the TRM the McSPI is tied to the CORE_48M_FCLK only, which I am not sure of the consequences of running at a different frequency, this same signal also goes to the UARTs so it may cause problems there as well, I am not sure how changing this would impact the USB peripheral. The datasheet makes no mention of a spec for CORE_48M_FCLK I can find, but the label implies it operates at 48MHz. I would probably try messing with the PRCM settings to see if you can get a 52MHz CORE_48M_FCLK on a dev board (for a /4 13MHz SPI), and see what it does to the rest of the system before committing to anything in hardware.

    Optimally if you could run at 12MHz that would be best if you need master capabilities, if you need 13 MHz exclusively the easiest way would probably be to run the McSPI as the slave to an external clock master if that is possible.

  • 0 in reply to Bernie Thompson TI
    Prodigy 195 points

    Hi Bernie, thanks for your answer.

    I am using Mistral Board to develop and I configure the McSPI to work in 13 MHz properly (correct), this isn't really the problem. My problem is using USB Host because, as long as I know, you must use a 48 MHz clock. If I mistaken correct me please. So the problem is set the USB as 28 MHz and McSPI as 13 MHz at the same time and I can't change McSPI to another frequency.

    I see that suggest to use a external clock trigger McSPI (slave mode). I will see if it's possible but I was thinking if it's possible to use a different clock in USB Host in a way that work for usual devices.

    Well I will study more the points you mention.

    Thanks a lot.