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Concerto- Serial loopback SCI boot mode-Drivelib-files

Christian L
Intellectual 630 points

Hi all,

I am using the serial loopback feature (connecting UART4 to C28x SCI) to bootload the C28x with an application using its SCI boot mode. Since there are no external connections, I wonder whether it is safe to not give the C28x ownership of GPIOs 35-36 in this case, allthough the SCI boot mode code assumes they are available. In other words, can I safely remove the following two lines in driverlib/ipc_util.c:

HWREG(GPIO_PORTF_BASE + GPIO_O_PUR) |= (GPIO_PIN_3 | GPIO_PIN_4);
HWREG(GPIO_PORTF_BASE + GPIO_O_CSEL) |= (GPIO_PIN_3 | GPIO_PIN_4);

See lines 220-221 where the case CBROM_MTOC_BOOTMODE_BOOT_FROM_SCI is handled.

It works fine and even seems to be more correct, that is, maybe these lines should be removed in the next release of the drivelib. But maybe I am overlooking something?

Thank you,

Christian

  • 0
    TI__Mastermind 32995 points
    Hi Christian,

    You should be able to remove those two lines in your application.

    We should not remove them from the ipc_util.c driver because that function, when called to boot the C28x to SCI, needs to give the C28x control of those GPIOs so that it can boot to SCI and communicate with an external device. In your application it is not necessary because you are using the internal loopback function. But, for other applications which are not using internal loopback, it is necessary.

    Best Regards,
    sal
  • 0 in reply to Sal Pezzino
    Intellectual 630 points
    Hi Sal,Thank you for confirming that it is ok to remove this lines in my case.
    Since the internal loopback is available and to my knowledge also used by many for bootloading, I think the function IPCMtoCBootControlSystem() within ipc_util.c should be modified to support and additional parameter value, for example called, CBROM_MTOC_BOOTMODE_BOOT_FROM_SCI_INTERNAL_LOOPBACK. This case could then be implemented as the existing case CBROM_MTOC_BOOTMODE_BOOT_FROM_SCI but without the unnecessary handing over of the two GPIOs 35-36.
    Anyway, many thanks for your quick reply.Christian
  • 0 in reply to Christian L
    TI__Mastermind 32995 points

    Hi Christian,

    Thanks for the suggestion.  Does the internal loopback bootloading work properly without commenting out those two lines which configure GPIO35/36??  

    sal

  • 0 in reply to Sal Pezzino
    Intellectual 630 points

    Hi Sal,

    yes, the bootloading itself work without removing these two lines, BUT it has certain side-effects which may cause serious problems. Specifically, during bootloding, GPIO35 will be the TX line of the C28x SCI where the received program is echoed back to the "master". If GPIO35 is used for other functionality (e.g., a LED under ARM control as it was in my case) this is off course a problem..

    Best regards,

    Christian