Issue Booting i.MX8MM Processor from eMMC - Power Down with USB-TTL Debugger Connected

[wooker]

I'm encountering an unusual problem while attempting to boot the i.MX8MM processor from the eMMC storage. According to the official documentation, the configuration involves setting the BOOTMODE0 and BOOTMODE1 pins to "Not Connected," along with specific settings for BT_CFG pins: BT_CFG[4,10,12] should be set to LOW, while BT_CFG[11,13] should be set to HIGH. Additionally, BOOT_MODE1 and BT_CFG[1,2,5] are connected with pull-up resistors.

However, I'm facing an unexpected scenario. When I set up the recommended configuration and connect the board to a USB-TTL debugger via UART2, the processor does not boot; instead, it powers down immediately. Intriguingly, when I disconnect the TX (transmit) line on the TTL, preventing any command transfer from the computer, the processor boots as expected from the eMMC.

I'm puzzled by this behavior. It seems that the presence of the USB-TTL debugger and the transmission of commands are somehow affecting the boot process. Could this be a communication conflict or interference causing the immediate power down?

I've verified the hardware connections and configurations as per the documentation, and everything appears to be in order. However, this peculiar issue persists only when the USB-TTL debugger is connected and actively transmitting commands.

Has anyone encountered a similar issue or can provide guidance on how to troubleshoot this specific scenario? Any insights, suggestions, or experiences related to i.MX8MM booting issues with USB-TTL debuggers would be greatly appreciated.

Thank you for your time and support.

[Dhruvit]

Hi @wooker,

I hope you are doing well.

Please make sure that BOOTMODE0 is pulled down using GND.

One can refer to i.MX8MM EVK design file for reference where UART2 is used for debug port.

i.MX 8M Mini LPDDR4 EVKB Base Board Design Files

Thanks & Regards,
Dhruvit Vasavada

[wooker]

Hello @Dhruvit,

Thank you for your message. I'm doing well, and I hope you are too.

Regarding the configuration, I want to confirm that BOOTMODE0 has been appropriately set by pulling it down to GND. This setup aligns with our design specifications. We've taken inspiration from the SCH-47712 version of i.MX8M Mini Reference Board attached below.

Are there any other aspects or considerations that you believe might help resolve the issue at hand? Any additional insights or alternative approaches you recommend exploring?

Thank you in advance!

[Dhruvit]

Hi @wooker,

Are there any bootlogs seen before the power reset on debug uart?

Please share the schematic of the custom board for further debugging.

Thanks & Regards,
Dhruvit Vasavada