IMX6UL UART RX short to ground

[umasundaram]

Hi,

   We have designed a PCB with IMX6UL(MCIMX6G2CVM05AA)  and PF3001. We normally update the binary in Uboot through the debug UART(UART1) port provided on the PCB.A FTDI 'UART to USB translator' is used for interface from our device to PC.

   We observe that on usage over a course of time,the UART RX line of processor is shorted to ground.We physically checked for the short on the PCB.But there was no physical shorts.

   As the UART RX was initially working fine and developed short over time, can you please let us know what can be source of this.Is there any suggestions need to be followed for prevention of this.

 Please find the attached part of schematic regarding debugging UART section.

Your suggestions are highly appreciated.

Thanks,

Uma

[umasundaram]

Hi ,

 Can you please let us know any updates on the issue.

Your help is highly appreciated.

Thanks,

Uma.

[umasundaram]

Hi Artur,

  Thanks for the response.

Please find attached the schematic pages of the IMX6UL_Debug UART interface, for your debugging.

Regards,

Uma.

[art]

The most likely cause of the issue is that the UART Tx/Rx lines on the processor side are powered from the 1.8V supply, as shown on the schematic you've provided, whereas the Tx/Rx lines of the FTDI UART to USB bridge are powered from the local 3.3V supply (not shown on the schematic), that's why the processor's Rx line became burnt out with time. This issue should be fixed on the design level.

Have a great day,
Artur

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[umasundaram]

Hi Artur,

   Thanks for the reply.As mentioned, we are operating the Debug UART port(UART1) in our design with 1.8V logic.Hence we have provided a level translator between FTDI USB-UART bridge.Please find the attached image for your reference.

   Can you please let us know the cause for the UART RX pin failure,over time.

Regards,

Uma

[art]

To make me able to do some case study, please provide the actual schematic, not only a block diagram.

Artur