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TM4C123FH6PM: Cannot set up booting to Boot Loader using jumper.

Oleg Kobrin
Expert 1890 points

Part Number: TM4C123FH6PM

Hello!

My design contains special jumper to set up firmvare update by entering boot loader. here is the schematic part:

The line BOOT/EXT_RST is multiplexed with reset for LCD. Measuring on pin 10 of CPU I see high level then no jumper installed and lo level with jumper.

I am configuring BOOTCFG as the following:

    uint32_t BCfg = 0xFFFFFFFE;
    BCfg &= ~FLASH_BOOTCFG_PORT_M;
    BCfg |= FLASH_BOOTCFG_PORT_D;
    BCfg &= ~FLASH_BOOTCFG_PIN_M;
    BCfg |= FLASH_BOOTCFG_PIN_7;
    //BCfg &= ~FLASH_BOOTCFG_POL;
    BCfg &= ~FLASH_BOOTCFG_EN;
    if(BCfg != HWREG(FLASH_BOOTCFG))
    {
        HWREG(FLASH_FMD) = BCfg;
        HWREG(FLASH_FMA) = 0x75100000;
        HWREG(FLASH_FMC) = FLASH_FMC_WRKEY | FLASH_FMC_COMT;
        while(HWREG(FLASH_FMC) & FLASH_FMC_COMT);
    }

Then line "BCfg &= ~FLASH_BOOTCFG_POL;" is commented, and POL bit is 1, device boots to application no matter, with or without jumper installed. Then I uncomment this line, boot loader is started regardless the jumper.

What is wrong?

  • 0
    TI__Guru*** 135355 points

    Hello Oleg,

    Configuration wise, it looks okay.

    Can you measure with an o-scope the voltage at the pin when you power up the device in both cases? I wonder if there is something going on hardware wise when the device boots up that is changing the level of the pin - especially due to the LCD connection.

  • 0 in reply to Ralph Jacobi
    Expert 1890 points

    Here is the scope screenshot for reset sequence. Blue is reset input, yellow is D7 input/output. As you see during reset D7 is alwais high, and remains high for 100 ms, until application is started and pulls reset down to initialize LCD. (sorry, time scale is not seen, but it is 50 ms per grid line). When jumper is installed D7 is alwais low, as jumper is shorting it to GND.

  • 0 in reply to Oleg Kobrin
    Expert 1890 points

    This is power up screenshot. As you see, D7 is alwais high too.

  • 0 in reply to Oleg Kobrin
    TI__Guru*** 135355 points

    Hello Oleg,

    Given the information presented here... as unlikely as it feels that the short low period is enough, can you try and test this functionality without the LCD screen connected and pulling that pin down? I don't see any other reason for this issue beyond that brief pull to low right now, and I would like to completely rule that out before trying to do further investigation.