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Original question:

TMS320F280021: Booting from SCI

TMS320F2800137: SCI Boot / AGPIO

Kris Parrent
Intellectual 850 points
Part Number: TMS320F2800137

Good afternoon,

I wanted to clarify the behavior of GPIO28 on F2800137RHBR. I am looking to use this pin for SCI boot as SCIA_RX as this is the default value for unprogrammed devices However, this pin is an AGPIO and has the following footnote in the datasheet which states it is by default unconnected.

(3) The GPIOs on these analog pins support full digital input and output functionality and are referred to as AGPIOs. By default, the AGPIOs are unconnected; that is, the analog and digital functions are both disabled. For configuration details, see the Digital Inputs and Outputs on ADC Pins (AGPIOs) section

Can you clarify what happens during the SCI boot mode execution? Will it read from GPIO28 on an unprogrammed device, or does it need to be programmed first?

Thanks!

  • 0
    TI__Mastermind 19795 points

    Hi Kris,

    Thanks for your question! Our serial bootloader expert is currently out of office, so I will let them confirm the following when the expert returns next week.

    But my understanding is that during the SCI boot execution, the appropriate default GPIO (GPIO28) is automatically configured as an SCI, with all necessary AGPIO configuration completed. So it will, during SCI boot, read the GPIO28 on an unprogrammed device. There is no additional programming that should be necessary first.

    Once you exit the boot-loader (and enter the main code) the SCI needs to be configured again, it will not stay configured past the boot sequence.

    Regards,

    Vince

  • 0 in reply to Vince
    Intellectual 850 points

    Thanks Vince. It seemed logical that it would have to work as you described, but I just wanted to make sure before spinning a board. I look forward to confirmation from the serial bootloader expert next week.

  • 0 in reply to Kris Parrent
    TI__Mastermind 19795 points

    Hi Kris,

    Just to keep you up to date, our expert will be back later this week and can provide an update at that time.

    Regards,

    Vince