not able to enter debug or reset controller

[sandeepa2]

Hi,

I am using MIMXRT1064-EVK, I have connected two uart ports through a FTDI converter to PC

- {pin_num: L13, pin_signal: GPIO_AD_B1_10, label: DEBUG1_Tx}
- {pin_num: J13, pin_signal: GPIO_AD_B1_11, label: DEBUG1_Rx}

- {pin_num: M11, pin_signal: GPIO_AD_B0_02, label: DEBUG2_Tx}
- {pin_num: G11, pin_signal: GPIO_AD_B0_03, label: DEBUG2_Rx}

I have only RX, TX & ground lines through these converters.

If I connect any of these cables first to Laptop, then the micro USB cable to Laptop, am neither able to enter debug session nor reset the controller.

But once I connect the USB cable first, enter debug session, then connect USB serial cables, then next time onwards I am able to use the reset button SW9 or use IDE to reset.

Any help would be appreciated. Thank you.

[Alexis_A]

Hello @sandeepa2,

Looking at these pins there's none that could cause the MCU to not boot. Could you confirm if there's any other connection or software in your project that could cause this issue?

Best Regards,

Alexis Andalon

[Aravind_R]

If we connect UART cables first to Laptop and then USB,we are able to measure only 832mV at MCU supply pins ,330mV at Reset pins and LED D20 is always ON.

[Alexis_A]

Hello @Aravind_R,

When the MCU is in an unpowered state, current injected through the device pins may bias internal device
structures (e.g. ESD diodes) and incorrectly power up these internal structures through inadvertent paths.
The presence of such residual voltage may influence different device-internal blocks in an unpredictable
manner and may ultimately result in unpredictable device behavior.

Once in the illegal state, powering up the device further and then applying reset does not necessarily clear
the illegal state.

So this should be the reason why the MCU doesn't boot with the presence of the FTDI.

Best Regards,

Alexis Andalon