iMX6 ul Boot mode question

[chrisszot]

I am using a iMX6UL and I am trying to boot from eMMC connected to SDIO2.  I am using a lot of GPIO's and do not want to use all of the LCD_DATA lines just for the boot configuration. 

I have installed two testpoints on the BOOT_MODE pins to allow us to enter serial flash mode with a test fixture, then when we remove the board from our test bench we pull these lines low to enable boot from fuses.

I am trying to understand the fusing details to ensure this works.  There are recommendations which state to leave the LCD_DATA lines open, or use a bunch of analogue switches to enable after boot to not enter an incorrect boot mode.  Is this really necessary?  If we enter serial mode, is there any way to boot from internal fuses and not use the GPIOs?  Or is fusing even needed/ could we boot off internal, have that be a bootloader to point to eMMC and set up the system correctly?

[igorpadykov · Accepted solution]

Hi Chris

after entering serial mode there no way to boot from internal fuses, as

processor will execute Serial Downloader commands, flow is described in

sect.8.9 Serial Downloader i.MX6UL Reference Manual (rev.1  4/2016)

http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6ULRM.pdf

Booting from fuses is described in sect.8.2.3 Boot From Fuses Mode

Best regards

igor

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