RT1064 - using multiple LPUARTs on power-up

[jason_lo]

We have designed a custom board using the RT1064 that mostly functions as expected.  In our design, we are using RT1064 LPUARTs 4, 6, and 8, which are connected to header pins.  

A problem we are observing is that when we reset the processor with devices connected to all the LPUART header pins, it halts and does not boot up.  However, if we only connect a single device to one out of the three LPUARTs (does not matter which one), the processor boots up without any problems.  And then upon successful boot-up, all LPUARTs function normally with any combination of devices attached.

Any ideas as to what could cause this from either the hardware or software side?

Thanks,

Jason

[jeremyzhou]

Hi  Jason Lo,

Thank you for your interest in NXP Semiconductor products and
for the opportunity to serve you.
According to your introduction, I guess this issue is related to the boot pins.
The below table provides boot options, functionality, fuse values, and associated pins. Please check the connected LPUART pins whether affect the value of the boot pins.

Have a great day,
TIC

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[jason_lo]

Thank you for response Jeremy.  We are using the following pins for LPUART functions.  I do not see any conflict with BOOT_CFG or BOOT_MODE pins.

• LPUART4_TX       = GPIO_EMC_19
• LPUART4_RX      = GPIO_EMC_20
• LPUART6_TX       = GPIO_EMC_25
• LPUART6_RX      = GPIO_EMC_26
• LPUART8_TX       = GPIO_EMC_38
• LPUART8_RX      = GPIO_EMC_39

To continue, I have also opened a support ticket.

Regards,

Jason

[jeremyzhou]

Hi  Jason Lo,

Thanks for your reply.
Maybe you can use the multimeter to monitor the above boot pins, and power supply pins, to check whether connecting LPUART4, 6,8 or not would change the value of these pins.

Have a great day,
TIC

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Note:
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- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
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