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IMX6UL - Serial downloader works only after first power-up

Question asked by ehwsma on Jul 16, 2018
Latest reply on Jul 19, 2018 by igorpadykov

Hi all,

 

We designed our custom board based on i.MX6UL processor, but I've got a strange behavior here :

 

  • When I power-up the board for the first time (Blank processor and flash), the Serial Downloader feature is available from the USB port and I'm able to load a custom u-boot image to RAM.



  • When I power the board OFF and ON (or use the "reset" command in u-boot), the HID USB interface for the Serial Downloader will not show again ! Instead, I'm having an "Unknown Device" appearing after a few seconds.

  • If I power the board OFF again and wait a few minutes, the Serial Downloader feature is available back immediately when I power the board ON.

 

Would you have any explanation to this strange behavior? This is very annoying both for debugging and for production process, as it looks not being very stable...

 

Thanks in advance.

 

Best regards

serial downloader protocol i.mx6ul

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