How to exit serial download mode with sdphost (RT1050)

[eric_yp_chen]

Hey @jeremyzhou 

Is it possible to exit serial download mode by using sdphost's write-register command ?

First, I've already upload bootable image into SPI flash through blhost.

After I send blhost --reset command , the device seems boot abnormally.

It boot into serial download mode again. However, if I re-plug in the power , or press the POR reset button. It can boot normally into my application.

I'd like to know what's wrong with this condition ?

BR,

Eric

[jeremyzhou]

Hi,
Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
1) I'd like to know what's wrong with this condition?
-- I think the source code of handling the Reset command can give us the answer.

//! @brief Reset command handler.
void handle_reset(uint8_t *packet, uint32_t packetLength)
{
    command_packet_t *commandPacket = (command_packet_t *)packet;
    send_generic_response(kStatus_Success, commandPacket->commandTag);

    // Wait for the ack from the host to the generic response
    g_bootloaderContext.activePeripheral->packetInterface->finalize(g_bootloaderContext.activePeripheral);

    // Prepare for shutdown.
    shutdown_cleanup(kShutdownType_Reset);
#if defined(BL_FEATURE_6PINS_PERIPHERAL) && BL_FEATURE_6PINS_PERIPHERAL
    shutdown_cleanup(kShutdownType_Cleanup);
#endif // BL_FEATURE_6PINS_PERIPHERAL

    NVIC_SystemReset();
    // Does not get here.
    assert(0);
}

After going through the code, we can find that the handle_reset function will execute the NVIC_SystemReset() to trigger a reset event, then MCU will boot from the mode which is determined by either boot pins or fuse set, and I think it can explain the phenomenon you encountered.
Have a great day,
TIC

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[eric_yp_chen]

Hi @jeremyzhou 

OK, I seem to know the problem.  First, I forced BOOT_CFG Pin = 01 to enter sdp mode.

After that, upload flashloader image and run. At this moment, even though I change pin setting to internal boot mode

while flashloader is still running. BOOT_CFG Pin setting will be only latch once after power-on reset.

Also, Blhost --reset command is not equal power-on reset. So, it will always boot into serial download mode.

Am I right ?

BR,

Eric

[jeremyzhou]

Hi,
Thanks for your reply.
1) Am I right?
-- No, I'm afraid not, I think the --reset command to force the MCU exit the Serial Download if the BOOT CFG pins were set to internal boot mode before.
Have a great day,
TIC

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[eric_yp_chen]

Hi @jeremyzhou 

My verification steps as below:  ( using IMXRT1050-EVKB)

1. Modify SW7 to 0001 (Set as serial download).

2. Use MCUBootUtility upload flashloader.

3. Use MCUBootUtility upload bootable image into nor-flash.

4. Modify SW7 to 0010 (Set as internal boot).

5. Press "reset device" button on MCUBootUtility --> this will trigger sending blhost --reset command

After these steps, mcu still stuck in serial download mode.

At this moment, you could try using this command "sdphost -t 50000 -u 0x1FC9,0x0130 -- read-register 1074757660 32 4"

This register represent SRC_SBMR2 which include BootMode Pin setting.

It always shows BootMode = 01, that means mcu didn't latch new setting when we sending blhost--reset

command through usb.

I've tried over 30 times or more..., the results were all the same.  BOOT_CFG Pin setting will be only latch once after POR_B hardware reset triggered. Otherwise it won't be changed.

You could try by yourself.

BR,

Eric

[jeremyzhou · Accepted solution]

Hi,
Thanks for sharing the detailed steps and I replicated the phenomenon on my side too.
According to the testing, we can jump to conclusion that the BOOT_MODE is initialized by sampling the BOOT_MODE0 and BOOT_MODE1 inputs on the rising edge of the POR_B.
Hope this is clear.
Have a great day,
TIC

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