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Original question:

TMS320F28379D: SCI flash programming on custom made hardware

TMS320F28379D: Use of GPIO84 for both SCI boot and boot selection switch

pravin n
Prodigy 40 points

Part Number: TMS320F28379D

Dear Team,

I need to burn .out file in F2837xD custom made board using SCI boot mode (GPIO 84 & GPIO85) with the help of Codeskin C2Prog utility. I read the related threads on forum but not satisfied by the conclusion. So my questions are:

1. GPIO84 is being used as boot selection switch and SCIA pin. I understand for boot mode selection it will be working as GPIO input and boot process as SCIATx (GPIO output) pin. Do I need to handle this direction configurations in my code? (if yes, how?) or will boot loader code will handle it by itself?

2. As per my understanding following circuit/ connection should work to implement the above scheme. Please verify and suggest any modification, if required.

  • 0
    TI__Genius 17370 points

    1. boot code will handle the necessary configurations.

    2. i will ask hw expert to comment on this

  • 0 in reply to Baskaran Chidambaram
    TI__Mastermind 19795 points

    Hi Pravin,

    Thanks for your question. For #2:

    The resistor divider formed when the switch is closed is sufficiently low voltage (~0.125V) to be below the VIL maximum of the datasheet for F2837xD (0.8V). So the divider switch itself should work.

    Now one concern that must be pointed out is that if the switch is accidentally left closed and is pulling GPIO84 (SCI-TX) low, it will likely cause break detect errors (since the driver may not be sufficiently driving high voltage between bytes).

    So essentially, if intending to utilize SCI-TX again, the switch should be opened again so that there is no pull-down on SCI-TX.

    Regards,

    Vince